diff --git a/2025-12-02.md b/2025-12-02.md new file mode 100644 index 0000000..566d492 --- /dev/null +++ b/2025-12-02.md @@ -0,0 +1,85 @@ +--- +id: +aliases: [] +tags: + - authorship/original + - destiny/permanent + - status/draft + - type/daily +title: 2025-12-02 +--- +# 2025-12-02 + +## 2025-12-02 10:40 + +> [!cite] [Hysteresis - Wikipedia](https://en.wikipedia.org/wiki/Hysteresis) +> **Hysteresis** is the dependence of the state of a system on its history. +> For example, a [magnet](https://en.wikipedia.org/wiki/Magnet "Magnet") +> may have more than one possible +> [magnetic moment](https://en.wikipedia.org/wiki/Magnetic_moment "Magnetic moment") +> in a given [magnetic field](https://en.wikipedia.org/wiki/Magnetic_field "Magnetic field"), +> depending on how the field changed in the past. +> Such a system is called **hysteretic**. + +![[alternating-current#Ferroelectric Hysteresis]] + +## 2025-12-02 10:57 + +Let $A$ and $B$ be sets +sharing some but not all elements. + +* $A \cap B \neq \varnothing$: + The intersection of $A$ and $B$ is nonempty + (They share at least one element). + +* $A \not\subseteq B$: + $A$ is not a subset of $B$ + ($A$ has at least one element not in $B$). + Equivalent to $A \setminus B \neq \varnothing$. + +* $B \not\subseteq A$: + $B$ is not a subset of $A$ + ($B$ has at least one element not in $A$). + Equivalent to $B \setminus A \neq \varnothing$. + +## 2025-12-02 13:20 + +### Panel Schedule Relationship Diagram + +#### Sections + +A panelboard with multiple sections +may or may not have multiple schedules. +`PANEL A1 SEC 1` + +#### Typical Schedules + +Schedules may be typical of multiple panelboards +`PANEL H(2-6)` + +## 2025-12-02 15:35 + +### Bluebeam Model Context Protocol Tools + +* add_view_port +* color_process_analyze +* color_process_modify +* count +* create_bookmarks +* create_markup_thumbnail +* get_markup_state +* get_page_count +* get_page_information +* list_markups_in_pdf +* list_state_models_in_pdf +* list_studio_projects +* list_studio_sessions +* open_file +* redact +* save_as_text +* search_and_markup +* set_markup_property +* set_markup_state +* set_page_labels +* stamp +* studio_project_search diff --git a/2025-12-03.md b/2025-12-03.md new file mode 100644 index 0000000..e1c58a7 --- /dev/null +++ b/2025-12-03.md @@ -0,0 +1,46 @@ +--- +id: +aliases: [] +tags: + - authorship/original + - destiny/permanent + - status/draft + - type/daily +title: 2025-12-03 +--- +# 2025-12-03 + +## 2025-12-03 15:54 + +There is a distinct difference between _excluding_ and _ignoring_ requirements. + +If, before award, you communicate to the customer +that your cost does not include respect for a requirement, +_and_ they understand the implications of the omission, +you have _excluded_ that requirement. + +If your cost does not include respect for a requirement, +but you have not communicated the omission to the customer +_and_ made a reasonable effort to inform them of the implications of its omission +you are _ignoring_ that requirement. + +_Excluding_ requirements is common practice. +_Ignoring_ requirements is unprofessional and irresponsible. + +Sometimes requirements are ignored out of convenience. +If an estimator is confident a requirement won't be enforced, +they may ignore it to lower the estimate and save time in closeout. +More ethical estimators may have no desire to do so, +but may nonetheless feel obligated to. +If a contractor is confident their competitors will ignore a requirement, +they may feel that the moral high road offers two losing options: + +* include it and appear overpriced +* exclude it and appear to present coverage concerns + +The winning strategy, as always, is open communication with the customer. + +> [!important] +> Given the same project documents and your proposal, +> a reasonably experienced estimator employed by your customer +> should be able to replicate your takeoff with confidence. diff --git a/alternating-current.md b/alternating-current.md index 1f78fb6..3926ec5 100644 --- a/alternating-current.md +++ b/alternating-current.md @@ -38,6 +38,8 @@ The voltage measured between any line and neutral is called **phase voltage**. ### Formula +#### Active Power + The formula for active power in a three phase system is given by $$ @@ -51,12 +53,18 @@ where: * $I_{L}$ is the line current, * $\text{PF}$ is the power factor. +#### Apparent Power + The formula for apparent power in a three phase system is given by $$ S = \sqrt{3} \times V_{L} \times I_{L} $$ +$$ +I_{L} = \frac{S}{\sqrt{3} \times V_{L}} +$$ + where: * $S$ is the apparent power, @@ -125,3 +133,10 @@ $$ Capacitance and inductance can both be measured in VAR, but their effects cancel each other out rather than add. + +## Ferroelectric Hysteresis + +The Venn Diagram of ferroelectric and ferromagnetic materials +has a large but not complete intersection. + + diff --git a/conductor-sizing.md b/conductor-sizing.md index e4bb7aa..0a49f4a 100644 --- a/conductor-sizing.md +++ b/conductor-sizing.md @@ -11,9 +11,18 @@ title: Conductor Sizing --- # Conductor Sizing +It is tempting to size circuit conductors +based on overcurrent protection, +but they are sized independently. + Conductors are sized to be suitable for the load, overcurrent protection is sized to protect the conductors. +Allowable conductor ampacity restrictions +are not based on a wire's ability to carry current, +they are intended to protect its insulation +from damage due to excessive heating. + ## "The 80% Rule" > [!danger] @@ -23,7 +32,7 @@ overcurrent protection is sized to protect the conductors. > that isn't preceded by a section reference, > it is _not_ code. > -> It is my opinion that this should never be repeated, +> It is my opinion that this one should never be repeated, > even as shorthand. "The 80% Rule" is a rule of thumb @@ -31,8 +40,12 @@ referring to a common convention of several articles including: * [[nfpa-70_210_branch-circuits#210.19(A)(1) General.]] + * [[nfpa-70_215_feeders#215.2(A)(1) General.]] +* [[nfpa-70_215_feeders#215.3 Overcurrent Protection.]] + * [[nfpa-70_430_motors#430.22 Single Motor.]] +* [[nfpa-70_430_motors#430.51 General.]] which paraphrased states: @@ -47,9 +60,9 @@ for 80% their listed rating, since 80% is the reciprocal of 125%. The rule neglects important context and common exceptions, -namely transformers, whose feeder conductors are sized at 100%. +namely transformers, whose feeder conductors are sized at 100%[^1]. -![[nfpa-70_215_feeders#215.2(B)(1) Feeders Supplying Transformers.]] +[^1]: [[nfpa-70_215_feeders#215.2(B)(1) Feeders Supplying Transformers.]] ## Branch Circuits @@ -81,7 +94,7 @@ or at least was at some point in the design. ## Feeders -![[nfpa-70_250_grounding-and-bonding#250.122(A) General.]] +![[nfpa-70_250_grounding#250.122(A) General.]] Apparently in the 2026 NEC First Draft Meetings, Code Making Panel 5 clarified that the equipment grounding conductor (EGC) diff --git a/electrical-takeoff.md b/electrical-takeoff.md index d3e7199..46800ce 100644 --- a/electrical-takeoff.md +++ b/electrical-takeoff.md @@ -19,6 +19,13 @@ title: Electrical Takeoff > [!tip] > Use [[heating-designations]] for uncertain scope. +## Garage + +In conventional slab garages, +use ENT and PVC as permitted. + +In precast slab garages, use EMT. + ## Lighting Control By PDI convention, [[lighting-controls-takeoff]] are generally "Electrical", not "Lighting". diff --git a/feeders-takeoff.md b/feeders-takeoff.md index b97ab6f..5a405e9 100644 --- a/feeders-takeoff.md +++ b/feeders-takeoff.md @@ -25,7 +25,7 @@ All feeder takeoff descriptions should be prefixed with ` TO ` > [!cite] Joel Jansen, in reference to Omni Hotels Raleigh (pp.) > It is acceptable to use typicals for identical feeders > (i.e. meter centers fed from bus plugs) -> so long as the typical is in the Feeders `Area`. +> so long as the typical is in `Area` = "01 - Feeders/Risers ...". ### Routing @@ -61,8 +61,14 @@ add 20ft in addition to previously mentioned adders. ## Feeders -`Area` = "01 - Feeders/Risers Building" -for all feeders, no matter the location. +* `Area` = "01 - Feeders/Risers Building" +* `Phase` = "Feeders" +* `System` = "FRR - Feeders and Risers" + +> [!info] Garage Feeders +> `Area` "01 - Feeders/Risers Garage" is seldom used. +> It may be appropriate for totally separate parking garage buildings. +> Seek clarification before using. ## Bus Duct @@ -70,7 +76,7 @@ for all feeders, no matter the location. ## Conductor Support -![[nfpa-70_300_general-requirements#300.19(A) Spacing Intervals -- Maximum.]] +![[nfpa-70_300_general-requirements#300.19(A) Spacing Intervals --- Maximum.]] `ITEM DATABASE`/`CONDUIT & FITTINGS`/`CABLE SUPPORT / WEDGES`/`... COMPLETE FITTING`/... diff --git a/fire-resistive-wiring-methods-takeoff.md b/fire-resistive-wiring-methods-takeoff.md index 8d55621..e2d55fe 100644 --- a/fire-resistive-wiring-methods-takeoff.md +++ b/fire-resistive-wiring-methods-takeoff.md @@ -21,3 +21,4 @@ or concrete-encasement can fulfill this requirement. If "Lifeline" (cable-in-conduit) cable is used, utilize EMT-Comp assemblies. + diff --git a/fire-resistive-wiring-methods.md b/fire-resistive-wiring-methods.md index 8dfff83..3b6439b 100644 --- a/fire-resistive-wiring-methods.md +++ b/fire-resistive-wiring-methods.md @@ -2,11 +2,11 @@ id: aliases: [] tags: - - authorship/original - - destiny/permanent - - status/incomplete - - topic/construction/electrical - - type/encyclopedia + - authorship/original + - destiny/permanent + - status/incomplete + - topic/construction/electrical + - type/encyclopedia title: Fire Resistive Wiring Methods --- # Fire Resistive Wiring Methods @@ -14,11 +14,12 @@ title: Fire Resistive Wiring Methods ## Requirements Permitted methods for fire protection of emergency feeders -are specified in 700.10(D)(1). +are specified in [[nfpa-70_700_emergency-systems#700.10(D)(2) Feeder-Circuit Wiring.|700.10(D)(2)]]. ![[nfpa-70_700_emergency-systems#700.10(D)(2) Feeder-Circuit Wiring.]] -the requirements of which only apply to occupancies listed in 700.10(D)(1) +the requirements of which only apply to occupancies listed in +[[nfpa-70_700_emergency-systems#700.10(D)(1) Occupancies.|700.10(D)(1)]] ![[nfpa-70_700_emergency-systems#700.10(D)(1) Occupancies.]] @@ -30,12 +31,43 @@ require fire protection, not [[nfpa-70_100_definitions#Branch Circuit.|branch ci > [!info] Keywords > * Low Smoke Zero Halogen (LSZH) -* Mineral Insulated (MI) Cable -* Fire Resistive Metal-Clad (MC) Cable -* Fire Resistive Cable-in-Conduit (CIC) +### Fire Resistive Metal-Clad (MC) Cable -> [!info] "Vitalink" vs "Lifeline" cable +[[nfpa-70_330_mc-cable|330 Metal-Clad Cable: Type MC]] + +### Mineral Insulated (MI) Cable + +[[nfpa-70_332_mi-cable|332 Mineral-Insulated, Metal-Sheathed Cable: Type MI]] + +When terminating single conductors in a ferrous metal enclosure, +it is necessary to terminate MI cables in a brass plate +to prevent heating due to ferroelectric hysteresis +Cut out and replace a section of the enclosure with the plate + +When cutting a hole in the enclosure would void its listing, +or is otherwise not allowed, +the cables can be terminated through a brass plate into a junction box +and power brought to the enclosure through a conventional raceway. + +> [!info] +> According to Pyrotenax literature, +> the intermediate junction box method is obligatory +> for fire pump controllers. + +### Fire Resistive Cable-in-Conduit (CIC) + +### Notes + +> [!info] "Vitalink" vs "Lifeline" cable ^vitalink-vs-lifeline > VITALink® and Lifeline® are brand names > (of Omni Cable and Prysmian Group respectively), > not cable types. > _Both_ brands include MC _and_ CIC cables. + +## Resources + +[VITALink Fire-Rated Cables | OmniCable](https://www.omnicable.com/vitalink/) + +[Lifeline® Fire Rated Cable Systems | Prysmian](https://na.prysmian.com/markets/electrification/industrial-and-construction/building-wire/fire-resistive-cable-systems) + +[Chemelex Pyrotenax](https://www.chemelex.com/en-us/pyrotenax) diff --git a/multi-family-dwellings.md b/multi-family-dwellings.md index 4c5388f..9894697 100644 --- a/multi-family-dwellings.md +++ b/multi-family-dwellings.md @@ -25,7 +25,9 @@ title: Multifamily Dwellings ### Are Hotels Multifamily Dwellings? > [!info] -> This question also applies to student housing and similar occupancies. +> This question also applies to student housing and similar occupancies, +> sometimes generalized as "hospitality", +> but this term is ambiguously understood. Whether hotel rooms are dwelling units and thus whether are hotels are multifamily dwellings per the NEC definition diff --git a/nfpa-70_100_definitions.md b/nfpa-70_100_definitions.md index 98d0246..022aac3 100644 --- a/nfpa-70_100_definitions.md +++ b/nfpa-70_100_definitions.md @@ -6,14 +6,15 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: Article 100 Definitions --- # Article 100 Definitions -**Scope.** +## Scope. + This article contains only those definitions essential to the application of this _Code_. It is not intended to include commonly defined general terms or commonly defined technical terms from related codes and standards. @@ -122,21 +123,21 @@ An organization, office, or individual responsible for enforcing the requirement or for approving equipment, materials, an installation, or a procedure. (CMP-1) -Informational Note: -The phrase "authority having jurisdiction," or its acronym AHJ, -is used in NFPA documents in a broad manner, -since jurisdictions and approval agencies vary, as do their responsibilities. -Where public safety is primary, -the authority having jurisdiction may be a federal, state, local, -or other regional department or individual -such as a fire chief; fire marshal; chief of a fire prevention bureau, -labor department, or health department; building official; electrical inspector; -or others having statutory authority. -For insurance purposes, an insurance inspection department, -rating bureau, or other insurance company representative -may be the authority having jurisdiction. -In many circumstances, the property owner or his or her designated agent assumes the role of the authority having jurisdiction; -at government installations, the commanding officer or departmental official may be the authority having jurisdiction. +> [!info] Informational Note: +> The phrase "authority having jurisdiction," or its acronym AHJ, +> is used in NFPA documents in a broad manner, +> since jurisdictions and approval agencies vary, as do their responsibilities. +> Where public safety is primary, +> the authority having jurisdiction may be a federal, state, local, +> or other regional department or individual +> such as a fire chief; fire marshal; chief of a fire prevention bureau, +> labor department, or health department; building official; electrical inspector; +> or others having statutory authority. +> For insurance purposes, an insurance inspection department, +> rating bureau, or other insurance company representative +> may be the authority having jurisdiction. +> In many circumstances, the property owner or his or her designated agent assumes the role of the authority having jurisdiction; +> at government installations, the commanding officer or departmental official may be the authority having jurisdiction. ### Automatic. diff --git a/nfpa-70_110_requirements-for-electrical-installations.md b/nfpa-70_110_requirements.md similarity index 99% rename from nfpa-70_110_requirements-for-electrical-installations.md rename to nfpa-70_110_requirements.md index 7faf674..612a540 100644 --- a/nfpa-70_110_requirements-for-electrical-installations.md +++ b/nfpa-70_110_requirements.md @@ -6,7 +6,7 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: Article 110 Requirements for Electrical Installations diff --git a/nfpa-70_210_branch-circuits.md b/nfpa-70_210_branch-circuits.md index 448c573..bbdfcc6 100644 --- a/nfpa-70_210_branch-circuits.md +++ b/nfpa-70_210_branch-circuits.md @@ -6,7 +6,7 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: Article 210 Branch Circuits @@ -23,7 +23,7 @@ This article provides the general requirements for branch circuits. Table 210.3 lists references for specific equipment and applications not located in Chapters 5, 6, and 7 that amend or supplement the requirements of this article. -Table 210.3 Specific-Purpose Branch Circuits +#### Table 210.3 Specific-Purpose Branch Circuits | Equipment | Article | Section | | --------------------------------------------------------------------------- | ------- | --------------------- | @@ -37,6 +37,13 @@ Table 210.3 Specific-Purpose Branch Circuits | Motors, motor circuits, and controllers | 430 | | | Switchboards and panelboards | | 408.52 | +%% +* [[nfpa-70_440_hvac-equipment#440.6 Ampacity and Rating.]] +* [[nfpa-70_440_hvac-equipment#440.31 General.]] +* [[nfpa-70_440_hvac-equipment#440.32 Single Motor-Compressor.]] +* [[nfpa-70_430_motors]] +%% + ### 210.4 Multiwire Branch Circuits. #### 210.4(A) General. @@ -453,21 +460,15 @@ All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets * c. The first outlet box in the branch circuit shall be marked to indicate that it is the first outlet of the circuit. * d. The combination of the branch-circuit overcurrent device and outlet branch-circuit AFCI shall be identified as meeting the requirements for a system combination-type AFCI and shall be listed as such. -* (5) If metal raceway, metal wireways, metal auxiliary gutters, or Type MC, or Type AC cable meeting the applicable requirements of -250.118, with metal boxes, metal conduit bodies, and metal enclosures are installed for the portion of the branch circuit between the branch-circuit overcurrent device and the first outlet, it shall be permitted to install a listed outlet branch-circuit-type AFCI at the first outlet to provide protection for the remaining portion of the branch circuit. +* (5) If metal raceway, metal wireways, metal auxiliary gutters, or Type MC, or Type AC cable meeting the applicable requirements of 250.118, with metal boxes, metal conduit bodies, and metal enclosures are installed for the portion of the branch circuit between the branch-circuit overcurrent device and the first outlet, it shall be permitted to install a listed outlet branch-circuit-type AFCI at the first outlet to provide protection for the remaining portion of the branch circuit. * (6) Where a listed metal or nonmetallic conduit or tubing or Type MC cable is encased in not less than 50 mm (2 in.) of concrete for the portion of the branch circuit between the branch-circuit overcurrent device and the first outlet, it shall be permitted to install a listed outlet branch-circuit-type AFCI at the first outlet to provide protection for the remaining portion of the branch circuit. > [!important] Exception: -> AFCI protection shall not be required for an individual branch circuit supplying a fire alarm system installed in accordance with 760.41(B) or 760.121(B). The branch circuit shall be installed in a metal raceway, metal auxiliary gutter, steel-armored cable, Type - -MC or Type AC, meeting the applicable requirements of 250.118, with metal boxes, conduit bodies, and enclosures. +> AFCI protection shall not be required for an individual branch circuit supplying a fire alarm system installed in accordance with 760.41(B) or 760.121(B). The branch circuit shall be installed in a metal raceway, metal auxiliary gutter, steel-armored cable, Type MC or Type AC, meeting the applicable requirements of 250.118, with metal boxes, conduit bodies, and enclosures. > [!info] Informational Note No. 1: -> For information on combination-type and branch/feeder-type arc-fault circuit interrupters, see UL 1699-2011, - -Standard for Arc-Fault Circuit Interrupters. For information on outlet branch-circuit type arc-fault circuit interrupters, see UL Subject -1699A, Outline of Investigation for Outlet Branch Circuit Arc-Fault Circuit-Interrupters. For information on system combination AFCIs, see UL Subject 1699C, Outline of Investigation for System Combination Arc-Fault Circuit Interrupters. +> For information on combination-type and branch/feeder-type arc-fault circuit interrupters, see UL 1699-2011, Standard for Arc-Fault Circuit Interrupters. For information on outlet branch-circuit type arc-fault circuit interrupters, see UL Subject 1699A, Outline of Investigation for Outlet Branch Circuit Arc-Fault Circuit-Interrupters. For information on system combination AFCIs, see UL Subject 1699C, Outline of Investigation for System Combination Arc-Fault Circuit Interrupters. > [!info] Informational Note No. 2: > See 29.6.3(5) of NFPA 72-2013, National Fire Alarm and Signaling Code, for information related to secondary power-supply requirements for smoke alarms installed in dwelling units. @@ -478,14 +479,10 @@ Standard for Arc-Fault Circuit Interrupters. For information on outlet branch-ci #### 210.12(B) Dormitory Units. All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets and devices installed in dormitory unit bedrooms, living rooms, hallways, closets, bathrooms, and similar rooms shall be protected by any of the means described in 210.12(A)(1) through (6). -210.12(C) Guest Rooms, Guest Suites, and Patient Sleeping Rooms in Nursing Homes and Limited-Care - -Facilities. +210.12(C) Guest Rooms, Guest Suites, and Patient Sleeping Rooms in Nursing Homes and Limited-Care Facilities. All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets and devices installed in guest rooms and guest suites of hotels and motels and patient sleeping rooms in nursing homes and limited-care facilities shall be protected by any of the means described in 210.12(A)(1) through (6). -210.12(D) Branch Circuit Extensions or Modifications --- Dwelling Units, Dormitory Units, and Guest - -Rooms and Guest Suites. +210.12(D) Branch Circuit Extensions or Modifications --- Dwelling Units, Dormitory Units, and Guest Rooms and Guest Suites. Where branch circuit wiring for any of the areas specified in 210.12(A), (B), or (C) is modified, replaced, or extended, the branch circuit shall be protected by one of the following: @@ -494,8 +491,7 @@ Where branch circuit wiring for any of the areas specified in 210.12(A), (B), or * (2) A listed outlet branch-circuit-type AFCI located at the first receptacle outlet of the existing branch circuit > [!important] Exception: -> AFCI protection shall not be required where the extension of the existing branch circuit conductors is not more than 1.8 m -(6 ft) and does not include any additional outlets or devices, other than splicing devices. This measurement shall not include the conductors inside an enclosure, cabinet, or junction box. +> AFCI protection shall not be required where the extension of the existing branch circuit conductors is not more than 1.8 m (6 ft) and does not include any additional outlets or devices, other than splicing devices. This measurement shall not include the conductors inside an enclosure, cabinet, or junction box. ### 210.13 Ground-Fault Protection of Equipment. @@ -553,7 +549,7 @@ shall determine the circuit rating. Branch-circuit conductors shall have an ampacity not less than the larger of 210.19(A)(1)(a) or (A)(1)(b) and comply with -[[nfpa-70_110_requirements-for-electrical-installations#110.14(C) Temperature Limitations.|110.14(C)]] +[[nfpa-70_110_requirements#110.14(C) Temperature Limitations.|110.14(C)]] for equipment terminations. * (a) Where a branch circuit supplies continuous loads @@ -594,8 +590,7 @@ Branch-circuit conductors supplying household ranges, wall-mounted ovens, counte ##### 210.19(A)(4) Other Loads. -Branch-circuit conductors that supply loads other than those specified in 210.3 and other than cooking appliances as covered in -210.19(A)(3) shall have an ampacity sufficient for the loads served and shall not be smaller than 14 AWG. +Branch-circuit conductors that supply loads other than those specified in 210.3 and other than cooking appliances as covered in 210.19(A)(3) shall have an ampacity sufficient for the loads served and shall not be smaller than 14 AWG. > [!important] Exception No. 1: > Tap conductors shall have an ampacity sufficient for the load served. In addition, they shall have an ampacity of not less than 15 for circuits rated less than 40 amperes and not less than 20 for circuits rated at 40 or 50 amperes and only where these tap conductors supply any of the following loads: @@ -615,11 +610,13 @@ Branch-circuit conductors that supply loads other than those specified in 210.3 #### 210.19(B) Branch Circuits Over 600 Volts. -The ampacity of conductors shall be in accordance with 310.14 and 311.60, as applicable. Branch-circuit conductors over 600 volts shall be sized in accordance with 210.19(B)(1) or (B)(2). +The ampacity of conductors shall be in accordance with 310.14 and 311.60, as applicable. +Branch-circuit conductors over 600 volts shall be sized in accordance with 210.19(B)(1) or (B)(2). ##### 210.19(B)(1) General. -The ampacity of branch-circuit conductors shall not be less than 125 percent of the designed potential load of utilization equipment that will be operated simultaneously. +The ampacity of branch-circuit conductors +shall not be less than 125 percent of the designed potential load of utilization equipment that will be operated simultaneously. ##### 210.19(B)(2) Supervised Installations. @@ -1225,7 +1222,7 @@ shall be located within the same room or area as the service equipment. ##### 210.63(B)(2) Indoor Equipment Requiring Dedicated Equipment Spaces. Where equipment, other than service equipment, -requires dedicated equipment space as specified in [[nfpa-70_110_requirements-for-electrical-installations#110.26(E) Dedicated Equipment Space.|110.26(E)]], +requires dedicated equipment space as specified in [[nfpa-70_110_requirements#110.26(E) Dedicated Equipment Space.|110.26(E)]], the required receptacle outlet shall be located within the same room or area as the electrical equipment and shall not be connected to the load side of the equipment's branch-circuit disconnecting means. diff --git a/nfpa-70_215_feeders.md b/nfpa-70_215_feeders.md index ac43931..ae99b0f 100644 --- a/nfpa-70_215_feeders.md +++ b/nfpa-70_215_feeders.md @@ -6,7 +6,7 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: Article 215 Feeders @@ -44,7 +44,6 @@ and shall comply with 110.14(C). > [!important] Exception No. 3: > Grounded conductors that are not connected to an overcurrent device shall be permitted to be sized at 100 percent of the continuous and noncontinuous load. - * (b) The minimum feeder conductor size shall have an ampacity not less than the maximum load to be served after the application of any adjustment or correction factors @@ -62,7 +61,10 @@ and shall comply with 110.14(C). ##### 215.2(A)(2) Grounded Conductor. -The size of the feeder circuit grounded conductor shall not be smaller than that required by 250.122, except that 250.122(F) shall not apply where grounded conductors are run in parallel. +The size of the feeder circuit grounded conductor +shall not be smaller than that required by [[nfpa-70_250_grounding#250.122 Size of Equipment Grounding Conductors.|250.122]], +except that [[nfpa-70_250_grounding#250.122(F) Conductors in Parallel.|250.122(F)]] +shall not apply where grounded conductors are run in parallel. Additional minimum sizes shall be as specified in 215.2(A)(3) under the conditions stipulated. @@ -77,7 +79,8 @@ The ampacity of conductors shall be in accordance with 310.14 and 311.60 as appl ##### 215.2(B)(1) Feeders Supplying Transformers. The ampacity of feeder conductors -shall not be less than the sum of the nameplate ratings of the transformers supplied +shall not be less than the sum +of the nameplate ratings of the transformers supplied when only transformers are supplied. ##### 215.2(B)(2) Feeders Supplying Transformers and Utilization Equipment. @@ -90,22 +93,37 @@ that will be operated simultaneously. ##### 215.2(B)(3) Supervised Installations. -For supervised installations, feeder conductor sizing shall be permitted to be determined by qualified persons under engineering supervision in accordance with 310.14(B) or 311.60(B). Supervised installations are defined as those portions of a facility where all of the following conditions are met: +For supervised installations, feeder conductor sizing shall be permitted +to be determined by qualified persons under engineering supervision +in accordance with 310.14(B) or 311.60(B). +Supervised installations are defined as those portions of a facility +where all of the following conditions are met: * (1) Conditions of design and installation are provided under engineering supervision. -* (2) Qualified persons with documented training and experience in over 1000-volt systems provide maintenance, monitoring, and servicing of the system. +* (2) Qualified persons with documented training and experience + in over 1000-volt systems provide maintenance, + monitoring, and servicing of the system. ### 215.3 Overcurrent Protection. -Feeders shall be protected against overcurrent in accordance with Part I of Article 240. Where a feeder supplies continuous loads or any combination of continuous and noncontinuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load. +Feeders shall be protected against overcurrent +in accordance with [[nfpa-70_240_overcurrent-protection#Part I. General|Part I of Article 240]]. +Where a feeder supplies continuous loads +or any combination of continuous and noncontinuous loads, +the rating of the overcurrent device +shall not be less than the noncontinuous load +plus 125 percent of the continuous load. > [!important] Exception: -> Where the assembly, including the overcurrent devices protecting the feeder(s), is listed for operation at 100 percent of its rating, the ampere rating of the overcurrent device shall be permitted to be not less than the sum of the continuous load plus the noncontinuous load. +> Where the assembly, including the overcurrent devices protecting the feeder(s), +> is listed for operation at 100 percent of its rating, +> the ampere rating of the overcurrent device +> shall be permitted to be not less than the sum of the continuous load +> plus the noncontinuous load. ### 215.4 Feeders with Common Neutral Conductor. - #### 215.4(A) Feeders with Common Neutral. Up to three sets of 3-wire feeders or two sets of 4-wire or 5-wire feeders shall be permitted to utilize a common neutral. @@ -116,9 +134,15 @@ Where installed in a metal raceway or other metal enclosure, all conductors of a ### 215.5 Diagrams of Feeders. -If required by the authority having jurisdiction, a diagram showing feeder details shall be provided prior to the installation of the feeders. +If required by the authority having jurisdiction, +a diagram showing feeder details +shall be provided prior to the installation of the feeders. -Such a diagram shall show the area in square feet of the building or other structure supplied by each feeder, the total calculated load before applying demand factors, the demand factors used, the calculated load after applying demand factors, and the size and type of conductors to be used. +Such a diagram shall show the area in square feet +of the building or other structure supplied by each feeder, +the total calculated load before applying demand factors, +the demand factors used, the calculated load after applying demand factors, +and the size and type of conductors to be used. ### 215.6 Feeder Equipment Grounding Conductor. @@ -127,7 +151,7 @@ in which equipment grounding conductors are required, the feeder shall include or provide an equipment grounding conductor, to which the equipment grounding conductors of the branch circuits shall be connected. Where the feeder supplies a separate building or structure, -the requirements of [[nfpa-70_250_grounding-and-bonding#250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).|250.32]] shall apply. +the requirements of [[nfpa-70_250_grounding#250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).|250.32]] shall apply. ### 215.7 Ungrounded Conductors Tapped from Grounded Systems. @@ -165,7 +189,6 @@ Feeders shall not be derived from autotransformers unless the system supplied ha ### 215.12 Identification for Feeders. - #### 215.12(A) Grounded Conductor. The grounded conductor of a feeder, if insulated, shall be identified in accordance with 200.6. @@ -196,7 +219,7 @@ Where a feeder is supplied from a dc system operating at more than 60 volts, eac * (1) A continuous red outer finish - * (2) A continuous red stripe durably marked along the conductor’s entire length on insulation of a color other than green, white, gray, or black + * (2) A continuous red stripe durably marked along the conductor's entire length on insulation of a color other than green, white, gray, or black * (3) Imprinted plus signs (+) or the word POSITIVE or POS durably marked on insulation of a color other than green, white, gray, or black, and repeated at intervals not exceeding 610 mm (24 in.) in accordance with 310.8(B) @@ -206,8 +229,8 @@ Where a feeder is supplied from a dc system operating at more than 60 volts, eac * (1) A continuous black outer finish - * (2) A continuous black stripe durably marked along the conductor’s entire length on insulation of a color other than green, white, gray, or red + * (2) A continuous black stripe durably marked along the conductor's entire length on insulation of a color other than green, white, gray, or red - * (3) Imprinted minus signs (–) or the word NEGATIVE or NEG durably marked on insulation of a color other than green, white, gray, or red, and repeated at intervals not exceeding 610 mm (24 in.) in accordance with 310.8(B) + * (3) Imprinted minus signs (--) or the word NEGATIVE or NEG durably marked on insulation of a color other than green, white, gray, or red, and repeated at intervals not exceeding 610 mm (24 in.) in accordance with 310.8(B) - * (4) An approved permanent marking means such as sleeving or shrink-tubing that is suitable for the conductor size, at all termination, connection, and splice points, with imprinted minus signs (–) or the word NEGATIVE or NEG durably marked on insulation of a color other than green, white, gray, or red + * (4) An approved permanent marking means such as sleeving or shrink-tubing that is suitable for the conductor size, at all termination, connection, and splice points, with imprinted minus signs (--) or the word NEGATIVE or NEG durably marked on insulation of a color other than green, white, gray, or red diff --git a/nfpa-70_220_load-calculations.md b/nfpa-70_220_load-calculations.md index 241839b..1257048 100644 --- a/nfpa-70_220_load-calculations.md +++ b/nfpa-70_220_load-calculations.md @@ -6,7 +6,7 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: Article 220 Branch-Circuit, Feeder, and Service Load Calculations diff --git a/nfpa-70_230_services.md b/nfpa-70_230_services.md index b32ebc0..03e602a 100644 --- a/nfpa-70_230_services.md +++ b/nfpa-70_230_services.md @@ -6,7 +6,7 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: Article 230 Services diff --git a/nfpa-70_240_overcurrent-protection.md b/nfpa-70_240_overcurrent-protection.md index 0836caf..76e3de0 100644 --- a/nfpa-70_240_overcurrent-protection.md +++ b/nfpa-70_240_overcurrent-protection.md @@ -6,7 +6,7 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: Article 240 Overcurrent Protection @@ -33,9 +33,9 @@ covers overcurrent protection over 1000 volts, nominal. > is provided to open the circuit if the current reaches a value > that will cause an excessive or dangerous temperature > in conductors or conductor insulation. -> See also [[nfpa-70_110_requirements-for-electrical-installations#110.9 Interrupting Rating.|110.9]] +> See also [[nfpa-70_110_requirements#110.9 Interrupting Rating.|110.9]] > for requirements for interrupting ratings -> and [[nfpa-70_110_requirements-for-electrical-installations#110.10 Circuit Impedance, Short-Circuit Current Ratings, and Other Characteristics.|110.10]] +> and [[nfpa-70_110_requirements#110.10 Circuit Impedance, Short-Circuit Current Ratings, and Other Characteristics.|110.10]] > for requirements for protection against fault currents. ### 240.2 Definitions. @@ -160,7 +160,11 @@ Where the overcurrent device is rated over 800 amperes, the ampacity of the cond #### 240.4(D) Small Conductors. -Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not exceed that required by (D)(1) through (D)(7) after any correction factors for ambient temperature and number of conductors have been applied. +Unless specifically permitted in [[#240.4(E) Tap Conductors.|240.4(E)]] +or [[#240.4(G) Overcurrent Protection for Specific Conductor Applications.|240.4(G)]], +the overcurrent protection shall not exceed that required by (D)(1) through (D)(7) +after any correction factors for ambient temperature +and number of conductors have been applied. ##### 240.4(D)(1) 18 AWG Copper. @@ -768,7 +772,7 @@ Where electric service and electrical maintenance are provided by the building m Overcurrent devices shall be located where they will not be exposed to physical damage. > [!info] Informational Note: -> See [[nfpa-70_110_requirements-for-electrical-installations#110.11 Deteriorating Agents.|110.11, Deteriorating Agents]] +> See [[nfpa-70_110_requirements#110.11 Deteriorating Agents.|110.11, Deteriorating Agents]] #### 240.24(D) Not in Vicinity of Easily Ignitible Material. diff --git a/nfpa-70_250_grounding-and-bonding.md b/nfpa-70_250_grounding.md similarity index 95% rename from nfpa-70_250_grounding-and-bonding.md rename to nfpa-70_250_grounding.md index f4255e8..da9557a 100644 --- a/nfpa-70_250_grounding-and-bonding.md +++ b/nfpa-70_250_grounding.md @@ -42,60 +42,60 @@ For other articles applying to particular cases of installation of conductors an #### Table 250.3 Additional Grounding and Bonding Requirements -| Conductor/Equipment | Article | Section | -| ------------------------------------------------------------------------------------------- | ------- | ------------------------------------------ | -| Agricultural buildings | | 547.9 and 547.10 | -| Audio signal processing, amplification, and reproduction equipment | | 640.7 | -| Branch circuits | | 210.5, 210.6, 406.3 | -| Cablebus | | 370.60 | -| Cable trays | 392 | 392.60 | -| Capacitors | | 460.10, 460.27 | -| Circuits and equipment operating at less than 50 volts | 720 | | -| Communications circuits | 800 | | -| Community antenna television and radio distribution systems | | 820.93, 820.100, 820.103, 800.106, 800.100 | -| Conductors for general wiring | 310 | | -| Medium voltage conductors and cables | 311 | | -| Cranes and hoists | 610 | | -| Electrically driven or controlled irrigation machines | | 675.11(C), 675.12, 675.13, 675.14, 675.15 | -| Electric signs and outline lighting | 600 | | -| Electrolytic cells | 668 | | -| Elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and stairway chairlifts | 620 | | -| Fixed electric heating equipment for pipelines and vessels | | 427.29, 427.48 | -| Fixed outdoor electric deicing and snow-melting equipment | | 426.27 | -| Flexible cords and cables | | 400.22, 400.23 | -| Floating buildings | | 555.54, 555.55, 555.56 | -| Grounding-type receptacles, adapters, cord connectors, and attachment plugs | | 406.10 | +| Conductor/Equipment | Article | Section | +| ------------------------------------------------------------------------------------------- | -------- | ------------------------------------------ | +| Agricultural buildings | | 547.9 and 547.10 | +| Audio signal processing, amplification, and reproduction equipment | | 640.7 | +| Branch circuits | | 210.5, 210.6, 406.3 | +| Cablebus | | 370.60 | +| Cable trays | 392 | 392.60 | +| Capacitors | | 460.10, 460.27 | +| Circuits and equipment operating at less than 50 volts | 720 | | +| Communications circuits | 800 | | +| Community antenna television and radio distribution systems | | 820.93, 820.100, 820.103, 800.106, 800.100 | +| Conductors for general wiring | 310 | | +| Medium voltage conductors and cables | 311 | | +| Cranes and hoists | 610 | | +| Electrically driven or controlled irrigation machines | | 675.11(C), 675.12, 675.13, 675.14, 675.15 | +| Electric signs and outline lighting | 600 | | +| Electrolytic cells | 668 | | +| Elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and stairway chairlifts | 620 | | +| Fixed electric heating equipment for pipelines and vessels | | 427.29, 427.48 | +| Fixed outdoor electric deicing and snow-melting equipment | | 426.27 | +| Flexible cords and cables | | 400.22, 400.23 | +| Floating buildings | | 555.54, 555.55, 555.56 | +| Grounding-type receptacles, adapters, cord connectors, and attachment plugs | | 406.10 | | Hazardous (classified) locations | 500--517 | | -| Health care facilities | 517 | | -| Induction and dielectric heating equipment | 665 | | -| Industrial machinery | 670 | | -| Information technology equipment | | 645.14, 645.15 | -| Intrinsically safe systems | | 504.50 | -| Luminaires and lighting equipment | | 410.40, 410.42, 410.46, 410.155(B) | -| Luminaires, lampholders, and lamps | 410 | | -| Marinas and boatyards | | 555.37, 555.38 | -| Mobile homes and mobile home park | 550 | | -| Motion picture and television studios and similar locations | | 530.20, 530.64(B) | -| Motors, motor circuits, and controllers | 430 | | -| Natural and artificially made bodies of water | 682 | 682.30, 682.31, 682.32, 682.33 | -| Network powered broadband communications circuits | | 800.100, 800.106, 830.93 | -| Optical fiber cables | | 770.100 | -| Outlet, device, pull, and junction boxes; conduit bodies; and fittings | | 314.4, 314.25 | -| Over 600 volts, nominal, underground wiring methods | | 300.50(C) | -| Panelboards | | 408.40 | -| Pipe organs | 650 | | -| Radio and television equipment | 810 | | -| Receptacles and cord connectors | | 406.3 | -| Recreational vehicles and recreational vehicle parks | 551 | | -| Services | 230 | | -| Solar photovoltaic systems | | 690.41, 690.42, 690.43, 690.45, 690.47 | -| Swimming pools, fountains, and similar installations | 680 | | -| Switchboards and panelboards | | 408.18(C) | -| Switches | | 404.12 | -| Theaters, audience areas of motion picture and television studios, and similar locations | | 520.81 | -| Transformers and transformer vaults | | 450.10 | -| Use and identification of grounded conductors | 200 | | -| X-ray equipment | 660 | 517.78 | +| Health care facilities | 517 | | +| Induction and dielectric heating equipment | 665 | | +| Industrial machinery | 670 | | +| Information technology equipment | | 645.14, 645.15 | +| Intrinsically safe systems | | 504.50 | +| Luminaires and lighting equipment | | 410.40, 410.42, 410.46, 410.155(B) | +| Luminaires, lampholders, and lamps | 410 | | +| Marinas and boatyards | | 555.37, 555.38 | +| Mobile homes and mobile home park | 550 | | +| Motion picture and television studios and similar locations | | 530.20, 530.64(B) | +| Motors, motor circuits, and controllers | 430 | | +| Natural and artificially made bodies of water | 682 | 682.30, 682.31, 682.32, 682.33 | +| Network powered broadband communications circuits | | 800.100, 800.106, 830.93 | +| Optical fiber cables | | 770.100 | +| Outlet, device, pull, and junction boxes; conduit bodies; and fittings | | 314.4, 314.25 | +| Over 600 volts, nominal, underground wiring methods | | 300.50(C) | +| Panelboards | | 408.40 | +| Pipe organs | 650 | | +| Radio and television equipment | 810 | | +| Receptacles and cord connectors | | 406.3 | +| Recreational vehicles and recreational vehicle parks | 551 | | +| Services | 230 | | +| Solar photovoltaic systems | | 690.41, 690.42, 690.43, 690.45, 690.47 | +| Swimming pools, fountains, and similar installations | 680 | | +| Switchboards and panelboards | | 408.18(C) | +| Switches | | 404.12 | +| Theaters, audience areas of motion picture and television studios, and similar locations | | 520.81 | +| Transformers and transformer vaults | | 450.10 | +| Use and identification of grounded conductors | 200 | | +| X-ray equipment | 660 | 517.78 | ### 250.4 General Requirements for Grounding and Bonding. @@ -569,7 +569,7 @@ A common grounding electrode conductor for multiple separately derived systems s * (1) A connector listed as grounding and bonding equipment. -* (2) Listed connections to aluminum or copper busbars not smaller than 6 mm thick × 50 mm wide (1⁄4 in. thick × 2 in. wide) and of sufficient length to accommodate the number of terminations necessary for the installation. If aluminum busbars are used, the installation shall also comply with 250.64(A). +* (2) Listed connections to aluminum or copper busbars not smaller than 6 mm thick × 50 mm wide (1/4 in. thick × 2 in. wide) and of sufficient length to accommodate the number of terminations necessary for the installation. If aluminum busbars are used, the installation shall also comply with 250.64(A). * (3) The exothermic welding process. @@ -792,7 +792,7 @@ One or more metal in-ground support structure(s) in direct contact with the eart A concrete-encased electrode shall consist of at least 6.0 m (20 ft) of either (1) or (2): -* (1) One or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (1⁄2 in.) in diameter, installed in one continuous 6.0 m (20 ft) length, or if in multiple pieces connected together by the usual steel tie wires, exothermic welding, welding, or other effective means to create a 6.0 m (20 ft) or greater length; or +* (1) One or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (1/2 in.) in diameter, installed in one continuous 6.0 m (20 ft) length, or if in multiple pieces connected together by the usual steel tie wires, exothermic welding, welding, or other effective means to create a 6.0 m (20 ft) or greater length; or * (2) Bare copper conductor not smaller than 4 AWG @@ -809,9 +809,9 @@ A ground ring encircling the building or structure, in direct contact with the e Rod and pipe electrodes shall not be less than 2.44 m (8 ft) in length and shall consist of the following materials. -* (a) Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3⁄4) and, where of steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection. +* (a) Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection. -* (b) Rod-type grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm (5⁄8 in.) in diameter, unless listed. +* (b) Rod-type grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm (5/8 in.) in diameter, unless listed. ##### 250.52(A)(6) Other Listed Electrodes. @@ -819,7 +819,7 @@ Other listed grounding electrodes shall be permitted. ##### 250.52(A)(7) Plate Electrodes. -Each plate electrode shall expose not less than 0.186 m (2 ft ) of surface to exterior soil. Electrodes of bare or electrically conductive coated iron or steel plates shall be at least 6.4 mm (1⁄4 in.) in thickness. Solid, uncoated electrodes of nonferrous metal shall be at least +Each plate electrode shall expose not less than 0.186 m (2 ft ) of surface to exterior soil. Electrodes of bare or electrically conductive coated iron or steel plates shall be at least 6.4 mm (1/4 in.) in thickness. Solid, uncoated electrodes of nonferrous metal shall be at least 1.5 mm (0.06 in.) in thickness. ##### 250.52(A)(8) Other Local Metal Underground Systems or Structures. @@ -1013,7 +1013,7 @@ A grounding electrode conductor tap shall extend to the inside of each disconnec * (2) Connectors listed as grounding and bonding equipment. -* (3) Connections to an aluminum or copper busbar not less than 6 mm thick × 50 mm wide (1⁄4 in. thick × 2 in. wide) and of sufficient length to accommodate the number of terminations necessary for the installation. The busbar shall be securely fastened and shall be installed in an accessible location. Connections shall be made by a listed connector or by the exothermic welding process. If aluminum busbars are used, the installation shall comply with 250.64(A). +* (3) Connections to an aluminum or copper busbar not less than 6 mm thick × 50 mm wide (1/4 in. thick × 2 in. wide) and of sufficient length to accommodate the number of terminations necessary for the installation. The busbar shall be securely fastened and shall be installed in an accessible location. Connections shall be made by a listed connector or by the exothermic welding process. If aluminum busbars are used, the installation shall comply with 250.64(A). ##### 250.64(D)(2) Individual Grounding Electrode Conductors. @@ -1065,7 +1065,7 @@ Grounding electrode conductor(s) and bonding jumpers interconnecting grounding e * (2) Grounding electrode conductor(s) shall be permitted to be run to one or more grounding electrode(s) individually. -* (3) Bonding jumper(s) from grounding electrode(s) shall be permitted to be connected to an aluminum or copper busbar not less than 6 mm thick × 50 mm wide (1⁄4 in. thick × 2 in wide.) and of sufficient length to accommodate the number of terminations necessary for the installation. The busbar shall be securely fastened and shall be installed in an accessible location. +* (3) Bonding jumper(s) from grounding electrode(s) shall be permitted to be connected to an aluminum or copper busbar not less than 6 mm thick × 50 mm wide (1/4 in. thick × 2 in wide.) and of sufficient length to accommodate the number of terminations necessary for the installation. The busbar shall be securely fastened and shall be installed in an accessible location. Connections shall be made by a listed connector or by the exothermic welding process. The grounding electrode conductor shall be permitted to be run to the busbar. Where aluminum busbars are used, the installation shall comply with 250.64(A). @@ -1259,7 +1259,7 @@ An intersystem bonding termination (IBT) for connecting intersystem bonding cond #### 250.94(B) Other Means. -Connections to an aluminum or copper busbar not less than 6 mm thick × 50 mm wide (1⁄4 in. thick × 2 in. wide) and of sufficient length to accommodate at least three terminations for communication systems in addition to other connections. The busbar shall be securely fastened and shall be installed in an accessible location. Connections shall be made by a listed connector. If aluminum busbars are used, the installation shall also comply with 250.64(A). +Connections to an aluminum or copper busbar not less than 6 mm thick × 50 mm wide (1/4 in. thick × 2 in. wide) and of sufficient length to accommodate at least three terminations for communication systems in addition to other connections. The busbar shall be securely fastened and shall be installed in an accessible location. Connections shall be made by a listed connector. If aluminum busbars are used, the installation shall also comply with 250.64(A). > [!important] Exception to (A) and (B): > Means for connecting intersystem bonding conductors are not required where communications systems are not likely to be used. @@ -1341,7 +1341,7 @@ Table 250.102(C)(1) Grounded Conductor, Main Bonding Jumper, System Bonding Jump Notes: -1. If the ungrounded supply conductors are larger than 1100 kcmil copper or 1750 kcmil aluminum, the grounded conductor or bonding jumper shall have an area not less than 12 1⁄2 percent of the area of the largest ungrounded supply conductor or equivalent area for parallel supply conductors. The grounded conductor or bonding jumper shall not be required to be larger than the largest ungrounded conductor or set of ungrounded conductors. +1. If the ungrounded supply conductors are larger than 1100 kcmil copper or 1750 kcmil aluminum, the grounded conductor or bonding jumper shall have an area not less than 12 1/2 percent of the area of the largest ungrounded supply conductor or equivalent area for parallel supply conductors. The grounded conductor or bonding jumper shall not be required to be larger than the largest ungrounded conductor or set of ungrounded conductors. 2. If the ungrounded supply conductors are larger than 1100 kcmil copper or 1750 kcmil aluminum and if the ungrounded supply conductors and the bonding jumper are of different materials (copper, aluminum, or copper-clad aluminum), the minimum size of the grounded conductor or bonding jumper shall be based on the assumed use of ungrounded supply conductors of the same material as the grounded conductor or bonding jumper and will have an ampacity equivalent to that of the installed ungrounded supply conductors. @@ -1647,14 +1647,14 @@ The equipment grounding conductor run with or enclosing the circuit conductors s * (5) Listed flexible metal conduit meeting all the following conditions: * a. The conduit is terminated in listed fittings. * b. The circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less. - * c. The size of the conduit does not exceed metric designator 35 (trade size 11⁄4). + * c. The size of the conduit does not exceed metric designator 35 (trade size 11/4). * d. The combined length of flexible metal conduit, flexible metallic tubing, and liquidtight flexible metal conduit in the same effective ground-fault current path does not exceed 1.8 m (6 ft). * e. If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, a wire-type equipment grounding conductor shall be installed. * (6) Listed liquidtight flexible metal conduit meeting all the following conditions: * a. The conduit is terminated in listed fittings. - * b. For metric designators 12 through 16 (trade sizes 3⁄8 through 1⁄2), the circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less. - * c. For metric designators 21 through 35 (trade sizes 3⁄4 through 11⁄4), the circuit conductors contained in the conduit are protected by overcurrent devices rated not more than 60 amperes and there is no flexible metal conduit, flexible metallic tubing, or liquidtight flexible metal conduit in metric designators 12 through 16 (trade sizes 3⁄8 through 1⁄2) in the effective ground-fault current path. + * b. For metric designators 12 through 16 (trade sizes 3/8 through 1/2), the circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less. + * c. For metric designators 21 through 35 (trade sizes 3/4 through 11/4), the circuit conductors contained in the conduit are protected by overcurrent devices rated not more than 60 amperes and there is no flexible metal conduit, flexible metallic tubing, or liquidtight flexible metal conduit in metric designators 12 through 16 (trade sizes 3/8 through 1/2) in the effective ground-fault current path. * d. The combined length of flexible metal conduit, flexible metallic tubing, and liquidtight flexible metal conduit in the same effective ground-fault current path does not exceed 1.8 m (6 ft). * e. If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, a wire-type equipment grounding conductor shall be installed. @@ -2228,7 +2228,7 @@ The minimum insulation level for neutral conductors of solidly grounded systems ##### 250.184(A)(2) Ampacity. -The neutral conductor shall be of sufficient ampacity for the load imposed on the conductor but not less than 331⁄3 percent of the ampacity of the phase conductors. +The neutral conductor shall be of sufficient ampacity for the load imposed on the conductor but not less than 331/3 percent of the ampacity of the phase conductors. > [!important] Exception: > In industrial and commercial premises under engineering supervision, it shall be permissible to size the ampacity of the neutral conductor to not less than 20 percent of the ampacity of the phase conductor. diff --git a/nfpa-70_300_general-requirements.md b/nfpa-70_300_general-requirements.md index 48fa1ac..6e41c93 100644 --- a/nfpa-70_300_general-requirements.md +++ b/nfpa-70_300_general-requirements.md @@ -47,11 +47,642 @@ Metric designators and trade sizes for conduit, tubing, and associated fittings | 129 | 5 | | 155 | 6 | - +Note: The metric designators and trade sizes are for identification purposes only and are not actual dimensions. + +### 300.2 Limitations. + +#### 300.2(A) Voltage. + +Wiring methods specified in Chapter 3 shall be used for 1000 volts, nominal, or less where not specifically limited in some section of Chapter 3. They shall be permitted for over 1000 volts, nominal, where specifically permitted elsewhere in this Code. + +#### 300.2(B) Temperature. + +Temperature limitation of conductors shall be in accordance with 310.14(A)(3). + +### 300.3 Conductors. + +#### 300.3(A) Single Conductors. + +Single conductors specified in Table 310.4(A) shall only be installed where part of a recognized wiring method of Chapter 3. + +> [!important] Exception: +> Individual conductors shall be permitted where installed as separate overhead conductors in accordance with 225.6. + +#### 300.3(B) Conductors of the Same Circuit. + +All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4). + +##### 300.3(B)(1) Paralleled Installations. + +Conductors shall be permitted to be run in parallel in accordance with the provisions of 310.10(G). The requirement to run all circuit conductors within the same raceway, auxiliary gutter, cable tray, trench, cable, or cord shall apply separately to each portion of the paralleled installation, and the equipment grounding conductors shall comply with 250.122. Connections, taps, or extensions made from paralleled conductors shall connect to all conductors of the paralleled set, grounded and ungrounded, as applicable. Parallel runs in cable trays shall comply with 392.20(C). + +> [!important] Exception: +> Conductors installed in nonmetallic raceways run underground shall be permitted to be arranged as isolated phase, neutral, and grounded conductor installations. The raceways shall be installed in close proximity, and the isolated phase, neutral, and grounded conductors shall comply with 300.20(B). + +##### 300.3(B)(2) Grounding and Bonding Conductors. + +Equipment grounding conductors shall be permitted to be installed outside a raceway or cable assembly where in accordance with the provisions of 250.130(C) for certain existing installations or in accordance with 250.134, Exception No. 2, for dc circuits. Equipment bonding conductors shall be permitted to be installed on the outside of raceways in accordance with 250.102(E). + +##### 300.3(B)(3) Nonferrous Wiring Methods. + +Conductors in wiring methods with a nonmetallic or other nonmagnetic sheath, where run in different raceways, auxiliary gutters, cable trays, trenches, cables, or cords, shall comply with 300.20(B). Conductors in single-conductor Type MI cable with a nonmagnetic sheath shall comply with 332.31. Conductors of single-conductor Type MC cable with a nonmagnetic sheath shall comply with 330.31, 330.116, and 300.20(B). + +##### 300.3(B)(4) Column-Width Panelboard Enclosures. + +Where an auxiliary gutter runs between a column-width panelboard and a pull box, and the pull box includes neutral terminations, the neutral conductors of circuits supplied from the panelboard shall be permitted to originate in the pull box. + +#### 300.3(C) Conductors of Different Systems. + +##### 300.3(C)(1) 1000 Volts, Nominal, or Less. + +Conductors of ac and dc circuits, rated 1000 volts, nominal, or less, shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway. + +Secondary wiring to electric-discharge lamps of 1000 volts or less, if insulated for the secondary voltage involved, shall be permitted to occupy the same luminaire, sign, or outline lighting enclosure as the branch-circuit conductors. + +> [!info] Informational Note No. 1: +> See 725.136(A) for Class 2 and Class 3 circuit conductors. + +> [!info] Informational Note No. 2: +> See 690.31(B) for photovoltaic source and output circuits. + +##### 300.3(C)(2) Over 1000 Volts, Nominal. + +Conductors of circuits rated over 1000 volts, nominal, shall not occupy the same equipment wiring enclosure, cable, or raceway with conductors of circuits rated 1000 volts, nominal, or less unless otherwise permitted in 300.3(C)(2)(a) through 300.3(C)(2)(d). + +* (a) Primary leads of electric-discharge lamp ballasts insulated for the primary voltage of the ballast, where contained within the individual wiring enclosure, shall be permitted to occupy the same luminaire, sign, or outline lighting enclosure as the branch-circuit conductors. + +* (b) Excitation, control, relay, and ammeter conductors used in connection with any individual motor or starter shall be permitted to occupy the same enclosure as the motor-circuit conductors. + +* (c) In motors, transformers, switchgear, switchboards, control assemblies, and similar equipment, conductors of different voltage ratings shall be permitted. + +* (d) In manholes, if the conductors of each system are permanently and effectively separated from the conductors of the other systems and securely fastened to racks, insulators, or other approved supports, conductors of different voltage ratings shall be permitted. + +Conductors having nonshielded insulation and operating at different voltage levels shall not occupy the same enclosure, cable, or raceway. + +### 300.4 Protection Against Physical Damage. + +Where subject to physical damage, conductors, raceways, and cables shall be protected. + +#### 300.4(A) Cables and Raceways Through Wood Members. + +##### 300.4(A)(1) Bored Holes. + +In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed through bored holes in joists, rafters, or wood members, holes shall be bored so that the edge of the hole is not less than 32 mm (1 1⁄4 in.) from the nearest edge of the wood member. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by screws or nails by a steel plate(s) or bushing(s), at least 1.6 mm (1⁄16 in.) thick, and of appropriate length and width installed to cover the area of the wiring. + +> [!important] Exception No. 1: +> Steel plates shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing. + +> [!important] Exception No. 2: +> A listed and marked steel plate less than 1.6 mm (1⁄16 in.) thick that provides equal or better protection against nail or screw penetration shall be permitted. + +##### 300.4(A)(2) Notches in Wood. + +Where there is no objection because of weakening the building structure, in both exposed and concealed locations, cables or raceways shall be permitted to be laid in notches in wood studs, joists, rafters, or other wood members where the cable or raceway at those points is protected against nails or screws by a steel plate at least 1.6 mm (1⁄16 in.) thick, and of appropriate length and width, installed to cover the area of the wiring. The steel plate shall be installed before the building finish is applied. + +> [!important] Exception No. 1: +> Steel plates shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing. + +> [!important] Exception No. 2: +> A listed and marked steel plate less than 1.6 mm (1⁄16 in.) thick that provides equal or better protection against nail or screw penetration shall be permitted. + +### 300.4(B) Nonmetallic-Sheathed Cables and Electrical Nonmetallic Tubing Through Metal Framing Members. + +##### 300.4(B)(1) Nonmetallic-Sheathed Cable. + +In both exposed and concealed locations where nonmetallic-sheathed cables pass through either factory- or field-punched, cut, or drilled slots or holes in metal members, the cable shall be protected by listed bushings or listed grommets covering all metal edges that are securely fastened in the opening prior to installation of the cable. + +##### 300.4(B)(2) Nonmetallic-Sheathed Cable and Electrical Nonmetallic Tubing. + +Where nails or screws are likely to penetrate nonmetallic-sheathed cable or electrical nonmetallic tubing, a steel sleeve, steel plate, or steel clip not less than 1.6 mm (1⁄16 in.) in thickness shall be used to protect the cable or tubing. + +> [!important] Exception: +> A listed and marked steel plate less than 1.6 mm (1⁄16 in.) thick that provides equal or better protection against nail or screw penetration shall be permitted. + +#### 300.4(C) Cables Through Spaces Behind Panels Designed to Allow Access. + +Cables or raceway-type wiring methods, installed behind panels designed to allow access, shall be supported according to their applicable articles. + +#### 300.4(D) Cables and Raceways Parallel to Framing Members and Furring Strips. + +In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed parallel to framing members, such as joists, rafters, or studs, or is installed parallel to furring strips, the cable or raceway shall be installed and supported so that the nearest outside surface of the cable or raceway is not less than 32 mm (1 1⁄4 in.) from the nearest edge of the framing member or furring strips where nails or screws are likely to penetrate. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by nails or screws by a steel plate, sleeve, or equivalent at least 1.6 mm (1⁄16 in.) thick. + +> [!important] Exception No. 1: +> Steel plates, sleeves, or the equivalent shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing. + +> [!important] Exception No. 2: +> For concealed work in finished buildings, or finished panels for prefabricated buildings where such supporting is impracticable, it shall be permissible to fish the cables between access points. + +> [!important] Exception No. 3: +> A listed and marked steel plate less than 1.6 mm (1⁄16 in.) thick that provides equal or better protection against nail or screw penetration shall be permitted. + +#### 300.4(E) Cables, Raceways, or Boxes Installed in or Under Roof Decking. + +A cable, raceway, or box, installed in exposed or concealed locations under metal-corrugated sheet roof decking, shall be installed and supported so there is not less than 38 mm (1 1⁄2 in.) measured from the lowest surface of the roof decking to the top of the cable, raceway, or box. A cable, raceway, or box shall not be installed in concealed locations in metal-corrugated, sheet decking–type roof. + +> [!info] Informational Note: +> Roof decking material is often repaired or replaced after the initial raceway or cabling and roofing installation and may be penetrated by the screws or other mechanical devices designed to provide “hold down” strength of the waterproof membrane or roof insulating material. + +> [!important] Exception: +> Rigid metal conduit and intermediate metal conduit shall not be required to comply with 300.4(E). + +#### 300.4(F) Cables and Raceways Installed in Shallow Grooves. + +Cable- or raceway-type wiring methods installed in a groove, to be covered by wallboard, siding, paneling, carpeting, or similar finish, shall be protected by 1.6 mm (1⁄16 in.) thick steel plate, sleeve, or equivalent or by not less than 32-mm (1 1⁄4-in.) free space for the full length of the groove in which the cable or raceway is installed. + +> [!important] Exception No. 1: +> Steel plates, sleeves, or the equivalent shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing. + +> [!important] Exception No. 2: +> A listed and marked steel plate less than 1.6 mm (1⁄16 in.) thick that provides equal or better protection against nail or screw penetration shall be permitted. + +#### 300.4(G) Fittings. + +Where raceways contain 4 AWG or larger insulated circuit conductors, and these conductors enter a cabinet, a box, an enclosure, or a raceway, the conductors shall be protected in accordance with any of the following: + +* (1) An identified fitting providing a smoothly rounded insulating surface + +* (2) A listed metal fitting that has smoothly rounded edges + +* (3) Separation from the fitting or raceway using an identified insulating material that is securely fastened in place + +* (4) Threaded hubs or bosses that are an integral part of a cabinet, box, enclosure, or raceway providing a smoothly rounded or flared entry for conductors + +Conduit bushings constructed wholly of insulating material shall not be used to secure a fitting or raceway. The insulating fitting or insulating material shall have a temperature rating not less than the insulation temperature rating of the installed conductors. + +#### 300.4(H) Structural Joints. + +A listed expansion/deflection fitting or other approved means shall be used where a raceway crosses a structural joint intended for expansion, contraction or deflection, used in buildings, bridges, parking garages, or other structures. + +### 300.5 Underground Installations. + +#### 300.5(A) Minimum Cover Requirements. + +Direct-buried cable, conduit, or other raceways shall be installed to meet the minimum cover requirements of Table 300.5. + +##### Table 300.5 Minimum Cover Requirements, 0 to 1000 Volts, Nominal, Burial in Millimeters (Inches) + +Type of Wiring Method or Circuit + +Location of Wiring + +Method or Circuit + +Column 1 + +Direct + +Burial + +Cables or + +Conductors + +Column 2 + +Rigid Metal + +Conduit or + +Intermediate + +Metal + +Conduit + +Column 3 + +Nonmetallic + +Raceways + +Listed for + +Direct Burial + +Without + +Concrete + +Encasement or Other + +Approved + +Raceways + +Column 4 + +Residential + +Branch Circuits + +Rated 120 Volts or Less with + +GFCI Protection and Maximum + +Overcurrent + +Protection of +20 Amperes + +Column 5 + +Circuits for Control of Irrigation and + +Landscape Lighting + +Limited to Not More + +Than 30 Volts and + +Installed with Type + +UF or in Other + +Identified Cable or + +Raceway mm in. mm in. mm in. mm in. mm in. + +All locations not specified below +600 24 150 6 450 18 300 12 150 6 + +In trench below 50 mm +(2 in.) thick concrete or equivalent +450 18 150 6 300 12 150 6 150 6 + +Under a building 0 0 0 0 0 0 0 0 0 0 +(in raceway or + +Type MC or + +Type MI cable identified for direct burial) +(in raceway or Type + +MC or Type MI cable identified for direct burial) +(in raceway or Type MC or + +Type MI cable identified for direct burial) + +Under minimum of 102 mm +(4 in.) thick concrete exterior slab with no vehicular traffic and the slab extending not less than 152 mm (6 in.) beyond the underground installation +450 18 100 4 100 4 150 6 150 6 +(direct burial) (direct burial) +100 4 100 4 +(in raceway) (in raceway) + +Under streets, highways, roads, alleys, driveways, and parking lots +600 24 600 24 600 24 600 24 600 24 + +One- and two-family dwelling driveways and outdoor parking areas, and used only for dwellingrelated purposes +450 18 450 18 450 18 300 12 450 18 + +In or under airport runways, including adjacent areas where trespassing prohibited +450 18 450 18 450 18 450 18 450 18 + +A lesser depth shall be permitted where specified in the installation instructions of a listed low-voltage lighting system. + +A depth of 150 mm (6 in.) shall be permitted for pool, spa, and fountain lighting, installed in a nonmetallic raceway, limited to not more than 30 volts where part of a listed low-voltage lighting system. + +Notes: +1. Cover is defined as the shortest distance in mm (in.) measured between a point on the top surface of any direct-buried conductor, cable, conduit, or other raceway and the top surface of finished grade, concrete, or similar cover. +2. Raceways approved for burial only where concrete encased shall require concrete envelope not less than 50 mm (2 in.) thick. +3. Lesser depths shall be permitted where cables and conductors rise for terminations or splices or where access is otherwise required. a, b a, b a b +4. Where one of the wiring method types listed in Columns 1 through 3 is used for one of the circuit types in Columns 4 and 5, the shallowest depth of burial shall be permitted. +5. Where solid rock prevents compliance with the cover depths specified in this table, the wiring shall be installed in a metal raceway, or a nonmetallic raceway permitted for direct burial. The raceways shall be covered by a minimum of 50 mm (2 in.) of concrete extending down to rock. + +#### 300.5(B) Wet Locations. + +The interior of enclosures or raceways installed underground shall be considered to be a wet location. Insulated conductors and cables installed in these enclosures or raceways in underground installations shall comply with 310.10(C). + +#### 300.5(C) Underground Cables and Conductors Under Buildings. + +Underground cable and conductors installed under a building shall be in a raceway. + +> [!important] Exception No. 1: +> Type MI cable shall be permitted under a building without installation in a raceway where embedded in concrete, fill, or other masonry in accordance with 332.10(6) or in underground runs where suitably protected against physical damage and corrosive conditions in accordance with 332.10(10). + +> [!important] Exception No. 2: +> Type MC cable listed for direct burial or concrete encasement shall be permitted under a building without installation in a raceway in accordance with 330.10(A)(5) and in wet locations in accordance with 330.10(A)(11). + +#### 300.5(D) Protection from Damage. + +Direct-buried conductors and cables shall be protected from damage in accordance with 300.5(D)(1) through (D)(4). + +##### 300.5(D)(1) Emerging from Grade. + +Direct-buried conductors and cables emerging from grade and specified in columns 1 and 4 of Table 300.5 shall be protected by enclosures or raceways extending from the minimum cover distance below grade required by 300.5(A) to a point at least 2.5 m (8 ft) above finished grade. In no case shall the protection be required to exceed 450 mm (18 in.) below finished grade. + +##### 300.5(D)(2) Conductors Entering Buildings. + +Conductors entering a building shall be protected to the point of entrance. + +##### 300.5(D)(3) Service Conductors. + +Underground service conductors that are not encased in concrete and that are buried 450 mm (18 in.) or more below grade shall have their location identified by a warning ribbon that is placed in the trench at least 300 mm (12 in.) above the underground installation. + +##### 300.5(D)(4) Enclosure or Raceway Damage. + +Where the enclosure or raceway is subject to physical damage, the conductors shall be installed in electrical metallic tubing, rigid metal conduit, intermediate metal conduit, RTRC-XW, Schedule 80 PVC conduit, or equivalent. + +#### 300.5(E) Splices and Taps. + +Direct-buried conductors or cables shall be permitted to be spliced or tapped without the use of splice boxes. The splices or taps shall be made in accordance with 110.14(B). + +#### 300.5(F) Backfill. + +Backfill that contains large rocks, paving materials, cinders, large or sharply angular substances, or corrosive material shall not be placed in an excavation where materials may damage raceways, cables, conductors, or other substructures or prevent adequate compaction of fill or contribute to corrosion of raceways, cables, or other substructures. + +Where necessary to prevent physical damage to the raceway, cable, or conductor, protection shall be provided in the form of granular or selected material, suitable running boards, suitable sleeves, or other approved means. + +#### 300.5(G) Raceway Seals. + +Conduits or raceways through which moisture may contact live parts shall be sealed or plugged at either or both ends. Spare or unused raceways shall also be sealed. Sealants shall be identified for use with the cable insulation, conductor insulation, bare conductor, shield, or other components. + +> [!info] Informational Note: +> Presence of hazardous gases or vapors may also necessitate sealing of underground conduits or raceways entering buildings. + +#### 300.5(H) Bushing. + +A bushing, or terminal fitting, with an integral bushed opening shall be used at the end of a conduit or other raceway that terminates underground where the conductors or cables emerge as a direct burial wiring method. A seal incorporating the physical protection characteristics of a bushing shall be permitted to be used in lieu of a bushing. + +#### 300.5(I) Conductors of the Same Circuit. + +All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors shall be installed in the same raceway or cable or shall be installed in close proximity in the same trench. + +> [!important] Exception No. 1: +> Conductors shall be permitted to be installed in parallel in raceways, multiconductor cables, or direct-buried single conductor cables. Each raceway or multiconductor cable shall contain all conductors of the same circuit, including equipment grounding conductors. Each direct-buried single conductor cable shall be located in close proximity in the trench to the other single conductor cables in the same parallel set of conductors in the circuit, including equipment grounding conductors. + +> [!important] Exception No. 2: +> Isolated phase, polarity, grounded conductor, and equipment grounding and bonding conductor installations shall be permitted in nonmetallic raceways or cables with a nonmetallic covering or nonmagnetic sheath in close proximity where conductors are paralleled as permitted in 310.10(G), and where the conditions of 300.20(B) are met. + +#### 300.5(J) Earth Movement. + +Where direct-buried conductors, raceways, or cables are subject to movement by settlement or frost, direct-buried conductors, raceways, or cables shall be arranged so as to prevent damage to the enclosed conductors or to equipment connected to the raceways. + +> [!info] Informational Note: +> This section recognizes “S” loops in underground direct burial cables and conductors to raceway transitions, expansion fittings in raceway risers to fixed equipment, and, generally, the provision of flexible connections to equipment subject to settlement or frost heaves. + +#### 300.5(K) Directional Boring. + +Cables or raceways installed using directional boring equipment shall be approved for the purpose. + +### 300.6 Protection Against Corrosion and Deterioration. + +Raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, fittings, supports, and support hardware shall be of materials suitable for the environment in which they are to be installed. + +#### 300.6(A) Ferrous Metal Equipment. + +Ferrous metal raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, metal elbows, couplings, nipples, fittings, supports, and support hardware shall be suitably protected against corrosion inside and outside (except threads at joints) by a coating of approved corrosion-resistant material. Where corrosion protection is necessary and the conduit is threaded in the field, the threads shall be coated with an approved electrically conductive, corrosion-resistant compound. + +> [!info] Informational Note: +> Field-cut threads are those threads that are cut in conduit, elbows, or nipples anywhere other than at the factory where the product is listed. + +> [!important] Exception: +> Stainless steel shall not be required to have protective coatings. + +##### 300.6(A)(1) Protected from Corrosion Solely by Enamel. + +Where protected from corrosion solely by enamel, ferrous metal raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, metal elbows, couplings, nipples, fittings, supports, and support hardware shall not be used outdoors or in wet locations as described in 300.6(D). + +##### 300.6(A)(2) Organic Coatings on Boxes or Cabinets. + +Where boxes or cabinets have an approved system of organic coatings and are marked “Raintight,” “Rainproof,” or “Outdoor Type,” they shall be permitted outdoors. + +##### 300.6(A)(3) In Concrete or in Direct Contact with the Earth. + +Ferrous metal raceways, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, nipples, fittings, supports, and support hardware shall be permitted to be installed in concrete or in direct contact with the earth, or in areas subject to severe corrosive influences where made of material approved for the condition, or where provided with corrosion protection approved for the condition. + +#### 300.6(B) Aluminum Metal Equipment. + +Aluminum raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, nipples, fittings, supports, and support hardware embedded or encased in concrete or in direct contact with the earth shall be provided with supplementary corrosion protection. + +#### 300.6(C) Nonmetallic Equipment. + +Nonmetallic raceways, cable trays, cablebus, auxiliary gutters, boxes, cables with a nonmetallic outer jacket and internal metal armor or jacket, cable sheathing, cabinets, elbows, couplings, nipples, fittings, supports, and support hardware shall be made of material approved for the condition and shall comply with 300.6(C)(1) and (C)(2) as applicable to the specific installation. + +##### 300.6(C)(1) Exposed to Sunlight. + +Where exposed to sunlight, the materials shall be listed as sunlight resistant or shall be identified as sunlight resistant. + +##### 300.6(C)(2) Chemical Exposure. + +Where subject to exposure to chemical solvents, vapors, splashing, or immersion, materials or coatings shall either be inherently resistant to chemicals based on their listing or be identified for the specific chemical reagent. + +#### 300.6(D) Indoor Wet Locations. + +In portions of dairy processing facilities, laundries, canneries, and other indoor wet locations, and in locations where walls are frequently washed or where there are surfaces of absorbent materials, such as damp paper or wood, the entire wiring system, where installed exposed, including all boxes, fittings, raceways, and cable used therewith, shall be mounted so that there is at least a 6-mm (1⁄4-in.) airspace between it and the wall or supporting surface. + +> [!important] Exception: +> Nonmetallic raceways, boxes, and fittings shall be permitted to be installed without the airspace on a concrete, masonry, tile, or similar surface. + +> [!info] Informational Note: +> In general, areas where acids and alkali chemicals are handled and stored may present such corrosive conditions, particularly when wet or damp. Severe corrosive conditions may also be present in portions of meatpacking plants, tanneries, glue houses, and some stables; in installations immediately adjacent to a seashore and swimming pool areas; in areas where chemical deicers are used; and in storage cellars or rooms for hides, casings, fertilizer, salt, and bulk chemicals. + +### 300.7 Raceways Exposed to Different Temperatures. + +#### 300.7(A) Sealing. + +Where portions of a raceway or sleeve are known to be subjected to different temperatures, and where condensation is known to be a problem, as in cold storage areas of buildings or where passing from the interior to the exterior of a building, the raceway or sleeve shall be sealed to prevent the circulation of warm air to a colder section of the raceway or sleeve. Sealants shall be identified for use with cable insulation, conductor insulation, a bare conductor, a shield, or other components. An explosionproof seal shall not be required for this purpose. + +#### 300.7(B) Expansion, Expansion-Deflection, and Deflection Fittings. + +Raceways shall be provided with expansion, expansion-deflection, or deflection fittings where necessary to compensate for thermal expansion, deflection, and contraction. + +> [!info] Informational Note: +> Table 352.44 and Table 355.44 provide the expansion information for polyvinyl chloride (PVC) and for reinforced thermosetting resin conduit (RTRC), respectively. A nominal number for steel conduit can be determined by multiplying the expansion length in Table 352.44 by 0.20. The coefficient of expansion for steel electrical metallic tubing, intermediate metal conduit, and rigid metal conduit is 1.170 × 10 (0.0000117 mm per mm of conduit for each °C in temperature change) \[0.650 × 10 (0.0000065 in. per inch of conduit for each °F in temperature change)\]. + +A nominal number for aluminum conduit and aluminum electrical metallic tubing can be determined by multiplying the expansion length in Table 352.44 by 0.40. The coefficient of expansion for aluminum electrical metallic tubing and aluminum rigid metal conduit is 2.34 × +10 (0.0000234 mm per mm of conduit for each °C in temperature change) \[1.30 × 10 (0.000013 in. per inch of conduit for each °F in temperature change)\]. + +### 300.8 Installation of Conductors with Other Systems. + +Raceways or cable trays containing electrical conductors shall not contain any pipe, tube, or equal for steam, water, air, gas, drainage, or any service other than electrical. + +### 300.9 Raceways in Wet Locations Abovegrade. + +Where raceways are installed in wet locations abovegrade, the interior of these raceways shall be considered to be a wet location. + +Insulated conductors and cables installed in raceways in wet locations abovegrade shall comply with 310.10(C). + +### 300.10 Electrical Continuity of Metal Raceways and Enclosures. + +Metal raceways, cable armor, and other metal enclosures for conductors shall be metallically joined together into a continuous electrical conductor and shall be connected to all boxes, fittings, and cabinets so as to provide effective electrical continuity. Unless specifically permitted elsewhere in this Code, raceways and cable assemblies shall be mechanically secured to boxes, fittings, cabinets, and other enclosures. +-5 -5 +-5 -5 + +> [!important] Exception No. 1: +> Short sections of raceways used to provide support or protection of cable assemblies from physical damage shall not be required to be made electrically continuous. + +> [!important] Exception No. 2: +> Equipment enclosures to be isolated, as permitted by 250.96(B), shall not be required to be metallically joined to the metal raceway. + +### 300.11 Securing and Supporting. + +#### 300.11(A) Secured in Place. + +Raceways, cable assemblies, boxes, cabinets, and fittings shall be securely fastened in place. + +#### 300.11(B) Wiring Systems Installed Above Suspended Ceilings. + +Support wires that do not provide secure support shall not be permitted as the sole support. Support wires and associated fittings that provide secure support and that are installed in addition to the ceiling grid support wires shall be permitted as the sole support. Where independent support wires are used, they shall be secured at both ends. Cables and raceways shall not be supported by ceiling grids. + +##### 300.11(B)(1) Fire-Rated Assemblies. + +Wiring located within the cavity of a fire-rated floor–ceiling or roof–ceiling assembly shall not be secured to, or supported by, the ceiling assembly, including the ceiling support wires. An independent means of secure support shall be provided and shall be permitted to be attached to the assembly. Where independent support wires are used, they shall be distinguishable by color, tagging, or other effective means from those that are part of the fire-rated design. + +> [!important] Exception: +> The ceiling support system shall be permitted to support wiring and equipment that have been tested as part of the fire-rated assembly. + +> [!info] Informational Note: +> One method of determining fire rating is testing in accordance with ANSI/ASTM E119-18b, Standard Test Methods for Fire Tests of Building Construction and Materials. + +##### 300.11(B)(2) Non–Fire-Rated Assemblies. + +Wiring located within the cavity of a non–fire-rated floor–ceiling or roof–ceiling assembly shall not be secured to, or supported by, the ceiling assembly, including the ceiling support wires. An independent means of secure support shall be provided and shall be permitted to be attached to the assembly. Where independent support wires are used, they shall be distinguishable by color, tagging, or other effective means. + +> [!important] Exception: +> The ceiling support system shall be permitted to support branch-circuit wiring and associated equipment where installed in accordance with the ceiling system manufacturer’s instructions. + +#### 300.11(C) Raceways Used as Means of Support. + +Raceways shall be used only as a means of support for other raceways, cables, or nonelectrical equipment under any of the following conditions: + +* (1) Where the raceway or means of support is identified as a means of support + +* (2) Where the raceway contains power supply conductors for electrically controlled equipment and is used to support Class 2 circuit conductors or cables that are solely for the purpose of connection to the equipment control circuits + +* (3) Where the raceway is used to support boxes or conduit bodies in accordance with 314.23 or to support luminaires in accordance with 410.36(E) + +#### 300.11(D) Cables Not Used as Means of Support. + +Cable wiring methods shall not be used as a means of support for other cables, raceways, or nonelectrical equipment. + +### 300.12 Mechanical Continuity — Raceways and Cables. + +Raceways, cable armors, and cable sheaths shall be continuous between cabinets, boxes, fittings, or other enclosures or outlets. + +> [!important] Exception No. 1: +> Short sections of raceways used to provide support or protection of cable assemblies from physical damage shall not be required to be mechanically continuous. + +> [!important] Exception No. 2: +> Raceways and cables installed into the bottom of open bottom equipment, such as switchboards, motor control centers, and floor or pad-mounted transformers, shall not be required to be mechanically secured to the equipment. + +### 300.13 Mechanical and Electrical Continuity — Conductors. + +#### 300.13(A) General. + +Conductors in raceways shall be continuous between outlets, boxes, devices, and so forth. There shall be no splice or tap within a raceway unless permitted by 300.15, 368.56(A), 376.56, 378.56, 384.56, 386.56, 388.56, or 390.56. + +#### 300.13(B) Device Removal. + +In multiwire branch circuits, the continuity of a grounded conductor shall not depend on device connections such as lampholders, receptacles, and so forth, where the removal of such devices would interrupt the continuity. + +### 300.14 Length of Free Conductors at Outlets, Junctions, and Switch Points. + +At least 150 mm (6 in.) of free conductor, measured from the point in the box where it emerges from its raceway or cable sheath, shall be left at each outlet, junction, and switch point for splices or the connection of luminaires or devices. Where the opening to an outlet, junction, or switch point is less than 200 mm (8 in.) in any dimension, each conductor shall be long enough to extend at least 75 mm +(3 in.) outside the opening. + +> [!important] Exception: +> Conductors that are not spliced or terminated at the outlet, junction, or switch point shall not be required to comply with +300.14. + +### 300.15 Boxes, Conduit Bodies, or Fittings — Where Required. + +A box shall be installed at each outlet and switch point for concealed knob-and-tube wiring. + +Fittings and connectors shall be used only with the specific wiring methods for which they are designed and listed. + +Where the wiring method is conduit, tubing, Type AC cable, Type MC cable, Type MI cable, nonmetallic-sheathed cable, or other cables, a box or conduit body shall be installed at each conductor splice point, outlet point, switch point, junction point, termination point, or pull point, unless otherwise permitted in 300.15(A) through (L). + +#### 300.15(A) Wiring Methods with Interior Access. + +A box or conduit body shall not be required for each splice, junction, switch, pull, termination, or outlet points in wiring methods with removable covers, such as wireways, multioutlet assemblies, auxiliary gutters, and surface raceways. The covers shall be accessible after installation. + +#### 300.15(B) Equipment. + +An integral junction box or wiring compartment as part of approved equipment shall be permitted in lieu of a box. + +#### 300.15(C) Protection. + +A box or conduit body shall not be required where cables enter or exit from conduit or tubing that is used to provide cable support or protection against physical damage. A fitting shall be provided on the end(s) of the conduit or tubing to protect the cable from abrasion. + +#### 300.15(D) Type MI Cable. + +A box or conduit body shall not be required where accessible fittings are used for straight-through splices in mineral-insulated metalsheathed cable. + +#### 300.15(E) Integral Enclosure. + +A wiring device with integral enclosure identified for the use, having brackets that securely fasten the device to walls or ceilings of conventional on-site frame construction, for use with nonmetallic-sheathed cable, shall be permitted in lieu of a box or conduit body. + +> [!info] Informational Note: +> See 334.30(C); 545.10; 550.15(I); 551.47(E), Exception No. 1; and 552.48(E), Exception No. 1. + +#### 300.15(F) Fitting. + +A fitting identified for the use shall be permitted in lieu of a box or conduit body where conductors are not spliced or terminated within the fitting. The fitting shall be accessible after installation, unless listed for concealed installation. + +#### 300.15(G) Direct-Buried Conductors. + +As permitted in 300.5(E), a box or conduit body shall not be required for splices and taps in direct-buried conductors and cables. + +#### 300.15(H) Insulated Devices. + +As permitted in 334.40(B), a box or conduit body shall not be required for insulated devices supplied by nonmetallic-sheathed cable. + +#### 300.15(I) Enclosures. + +A box or conduit body shall not be required where a splice, switch, terminal, or pull point is in a cabinet or cutout box, in an enclosure for a switch or overcurrent device as permitted in 312.8, in a motor controller as permitted in 430.10(A), or in a motor control center. + +#### 300.15(J) Luminaires. + +A box or conduit body shall not be required where a luminaire is used as a raceway as permitted in 410.64. + +#### 300.15(K) Embedded. + +A box or conduit body shall not be required for splices where conductors are embedded as permitted in 424.40, 424.41(D), 426.22(C), +426.24(A), and 427.19(A). + +#### 300.15(L) Manholes and Handhole Enclosures. + +A box or conduit body shall not be required for conductors in manholes or handhole enclosures, except where connecting to electrical equipment. The installation shall comply with the provisions of Part V of Article 110 for manholes, and 314.30 for handhole enclosures. + +### 300.16 Raceway or Cable to Open or Concealed Wiring. + +#### 300.16(A) Box, Conduit Body, or Fitting. + +A box, conduit body, or terminal fitting having a separately bushed hole for each conductor shall be used wherever a change is made from conduit, electrical metallic tubing, electrical nonmetallic tubing, nonmetallic-sheathed cable, Type AC cable, Type MC cable, or mineral-insulated, metal-sheathed cable and surface raceway wiring to open wiring or to concealed knob-and-tube wiring. A fitting used for this purpose shall contain no taps or splices and shall not be used at luminaire outlets. A conduit body used for this purpose shall contain no taps or splices, unless it complies with 314.16(C)(2). + +#### 300.16(B) Bushing. + +A bushing shall be permitted in lieu of a box or terminal where the conductors emerge from a raceway and enter or terminate at equipment, such as open switchboards, unenclosed control equipment, or similar equipment. The bushing shall be of the insulating type for other than lead-sheathed conductors. + +### 300.17 Number and Size of Conductors in Raceway. + +The number and size of conductors in any raceway shall not be more than will permit dissipation of the heat and ready installation or withdrawal of the conductors without damage to the conductors or to their insulation. + +> [!info] Informational Note: +> See the following sections of this Code: intermediate metal conduit, 342.22; rigid metal conduit, 344.22; flexible metal conduit, 348.22; liquidtight flexible metal conduit, 350.22; PVC conduit, 352.22; HDPE conduit, 353.22; RTRC, 355.22; liquidtight nonmetallic flexible conduit, 356.22; electrical metallic tubing, 358.22; flexible metallic tubing, 360.22; electrical nonmetallic tubing, +362.22; cellular concrete floor raceways, 372.22; cellular metal floor raceways, 374.22; metal wireways, 376.22; nonmetallic wireways, +378.22; surface metal raceways, 386.22; surface nonmetallic raceways, 388.22; underfloor raceways, 390.22; fixture wire, 402.7; theaters, 520.6; signs, 600.31(C); elevators, 620.33; audio signal processing, amplification, and reproduction equipment, 640.23(A) and +640.24; Class 1, Class 2, and Class 3 circuits, Article 725; fire alarm circuits, Article 760; and optical fiber cables and raceways, Article +770. + +### 300.18 Raceway Installations. + +#### 300.18(A) Complete Runs. + +Raceways, other than busways or exposed raceways having hinged or removable covers, shall be installed complete between outlet, junction, or splicing points prior to the installation of conductors. Where required to facilitate the installation of utilization equipment, the raceway shall be permitted to be initially installed without a terminating connection at the equipment. Prewired raceway assemblies shall be permitted only where specifically permitted in this Code for the applicable wiring method. + +> [!important] Exception: +> Short sections of raceways used to contain conductors or cable assemblies for protection from physical damage shall not be required to be installed complete between outlet, junction, or splicing points. + +#### 300.18(B) Welding. + +Metal raceways shall not be supported, terminated, or connected by welding to the raceway unless specifically designed to be or otherwise specifically permitted to be in this Code. + ### 300.19 Supporting Conductors in Vertical Raceways. -#### 300.19(A) Spacing Intervals -- Maximum. +#### 300.19(A) Spacing Intervals --- Maximum. Conductors in vertical [[nfpa-70_100_definitions#Raceway.|raceways]] shall be supported if the vertical rise exceeds the values in Table 300.19(A). @@ -104,3 +735,360 @@ One of the following methods of support shall be used: 4. Other approved means. + +### 300.20 Induced Currents in Ferrous Metal Enclosures or Ferrous Metal Raceways. + +#### 300.20(A) Conductors Grouped Together. + +Where conductors carrying alternating current are installed in ferrous metal enclosures or ferrous metal raceways, they shall be arranged so as to avoid heating the surrounding ferrous metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together. + +> [!important] Exception No. 1: +> Equipment grounding conductors for certain existing installations shall be permitted to be installed separate from their associated circuit conductors where run in accordance with the provisions of 250.130(C). + +> [!important] Exception No. 2: +> A single conductor shall be permitted to be installed in a ferromagnetic enclosure and used for skin-effect heating in accordance with the provisions of 426.42 and 427.47. + +#### 300.20(B) Individual Conductors. + +Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit. + +> [!important] Exception: +> In the case of circuits supplying vacuum or electric-discharge lighting systems or signs or X-ray apparatus, the currents carried by the conductors are so small that the inductive heating effect can be ignored where these conductors are placed in metal enclosures or pass through metal. + +> [!info] Informational Note: +> Because aluminum is not a magnetic metal, there will be no heating due to hysteresis; however, induced currents will be present. They will not be of sufficient magnitude to require grouping of conductors or special treatment in passing conductors through aluminum wall sections. + +### 300.21 Spread of Fire or Products of Combustion. + +Electrical installations in hollow spaces, vertical shafts, and ventilation or air-handling ducts shall be made so that the possible spread of fire or products of combustion will not be substantially increased. Openings around electrical penetrations into or through fireresistant-rated walls, partitions, floors, or ceilings shall be firestopped using approved methods to maintain the fire resistance rating. + +> [!info] Informational Note: +> Directories of electrical construction materials published by qualified testing laboratories contain many listing installation restrictions necessary to maintain the fire-resistive rating of assemblies where penetrations or openings are made. Building codes also contain restrictions on membrane penetrations on opposite sides of a fire-resistance-rated wall assembly. An example is the +600-mm (24-in.) minimum horizontal separation that usually applies between boxes installed on opposite sides of the wall. Assistance in complying with 300.21 can be found in building codes, fire resistance directories, and product listings. + +### 300.22 Wiring in Ducts Not Used for Air Handling, Fabricated Ducts for Environmental Air, and Other Spaces for Environmental Air (Plenums). + +The provisions of this section shall apply to the installation and uses of electrical wiring and equipment in ducts used for dust, loose stock, or vapor removal; ducts specifically fabricated for environmental air; and other spaces used for environmental air (plenums). + +> [!info] Informational Note: +> See Article 424, Part VI, for duct heaters. + +#### 300.22(A) Ducts for Dust, Loose Stock, or Vapor Removal. + +No wiring systems of any type shall be installed in ducts used to transport dust, loose stock, or flammable vapors. No wiring system of any type shall be installed in any duct, or shaft containing only such ducts, used for vapor removal or for ventilation of commercial-type cooking equipment. + +#### 300.22(B) Ducts Specifically Fabricated for Environmental Air. + +Equipment, devices, and the wiring methods specified in this section shall be permitted within such ducts only if necessary for the direct action upon, or sensing of, the contained air. Where equipment or devices are installed and illumination is necessary to facilitate maintenance and repair, enclosed gasketed-type luminaires shall be permitted. + +Only wiring methods consisting of Type MI cable without an overall nonmetallic covering, Type MC cable employing a smooth or corrugated impervious metal sheath without an overall nonmetallic covering, electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, or rigid metal conduit without an overall nonmetallic covering shall be installed in ducts specifically fabricated to transport environmental air. Flexible metal conduit shall be permitted, in lengths not to exceed 1.2 m (4 ft), to connect physically adjustable equipment and devices permitted to be in these fabricated ducts. The connectors used with flexible metal conduit shall effectively close any openings in the connection. + +> [!important] Exception: +> Wiring methods and cabling systems, listed for use in other spaces used for environmental air (plenums), shall be permitted to be installed in ducts specifically fabricated for environmental air-handling purposes under the following conditions: + +* (1) The wiring methods or cabling systems shall be permitted only if necessary to connect to equipment or devices associated with the direct action upon or sensing of the contained air, and + +* (2) The total length of such wiring methods or cabling systems shall not exceed 1.2 m (4 ft). + +#### 300.22(C) Other Spaces Used for Environmental Air (Plenums). + +This section shall apply to spaces not specifically fabricated for environmental air-handling purposes but used for air-handling purposes as a plenum. This section shall not apply to habitable rooms or areas of buildings, the prime purpose of which is not air handling. + +> [!info] Informational Note No. 1: +> The space over a hung ceiling used for environmental air-handling purposes is an example of the type of other space to which this section applies. + +> [!info] Informational Note No. 2: +> The phrase other spaces used for environmental air (plenum) as used in this section correlates with the use of the term plenum in NFPA 90A-2018, Standard for the Installation of Air-Conditioning and Ventilating Systems, and other mechanical codes where the plenum is used for return air purposes, as well as some other air-handling spaces. + +> [!important] Exception: +> This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such spaces. + +##### 300.22(C)(1) Wiring Methods. + +The wiring methods for such other space shall be limited to totally enclosed, nonventilated, insulated busway having no provisions for plug-in connections, Type MI cable without an overall nonmetallic covering, Type MC cable without an overall nonmetallic covering, + +Type AC cable, or other factory-assembled multiconductor control or power cable that is specifically listed for use within an air-handling space, or listed prefabricated cable assemblies of metallic manufactured wiring systems without nonmetallic sheath. Other types of cables, conductors, and raceways shall be permitted to be installed in electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, rigid metal conduit without an overall nonmetallic covering, flexible metal conduit, or, where accessible, surface metal raceway or metal wireway with metal covers. + +Nonmetallic cable ties and other nonmetallic cable accessories used to secure and support cables shall be listed as having low smoke and heat release properties. + +> [!info] Informational Note: +> One method to determine low smoke and heat release properties is that the nonmetallic cable ties and other nonmetallic cable accessories exhibit a maximum peak optical density of 0.50 or less, an average optical density of 0.15 or less, and a peak heat release rate of 100 kW or less when tested in accordance with ANSI/UL 2043-2008, Fire Test for Heat and Visible Smoke + +Release for Discrete Products and Their Accessories Installed in Air-Handling Spaces. + +##### 300.22(C)(2) Cable Tray Systems. + +The provisions in 300.22(C)(2)(a) or (C)(2)(b) shall apply to the use of metallic cable tray systems in other spaces used for environmental air (plenums), where accessible, as follows: + +* (a) Metal Cable Tray Systems. Metal cable tray systems shall be permitted to support the wiring methods in 300.22(C)(1). + +* (b) Solid Side and Bottom Metal Cable Tray Systems. Solid side and bottom metal cable tray systems with solid metal covers shall be permitted to enclose wiring methods and cables, not already covered in 300.22(C)(1), in accordance with 392.10(A) and (B). + +##### 300.22(C)(3) Equipment. + +Electrical equipment with a metal enclosure, or electrical equipment with a nonmetallic enclosure listed for use within an air-handling space and having low smoke and heat release properties, and associated wiring material suitable for the ambient temperature shall be permitted to be installed in such other space unless prohibited elsewhere in this Code. + +> [!info] Informational Note: +> One method to determine low smoke and heat release properties is that the equipment exhibits a maximum peak optical density of 0.50 or less, an average optical density of 0.15 or less, and a peak heat release rate of 100 kW or less when tested in accordance with ANSI/UL 2043-2013, Fire Test for Heat and Visible Smoke Release for Discrete Products and Their Accessories + +Installed in Air-Handling Spaces. + +> [!important] Exception: +> Integral fan systems shall be permitted where specifically identified for use within an air-handling space. + +#### 300.22(D) Information Technology Equipment. + +Where the installation complies with the special requirements in 645.4, electrical wiring in air-handling areas beneath raised floors for information technology equipment shall be permitted in accordance with 645.5(E). + +### 300.23 Panels Designed to Allow Access. + +Cables, raceways, and equipment installed behind panels designed to allow access, including suspended ceiling panels, shall be arranged and secured so as to allow the removal of panels and access to the equipment. + +### 300.25 Exit Enclosures (Stair Towers). + +Where an exit enclosure is required to be separated from the building, only electrical wiring methods serving equipment permitted by the authority having jurisdiction in the exit enclosure shall be installed within the exit enclosure. + +> [!info] Informational Note: +> For more information, refer to NFPA 101-2018, Life Safety Code, 7.1.3.2.1(10)(b). + +## Part II. Requirements for over 1000 Volts, Nominal + +### 300.31 Covers Required. + +Suitable covers shall be installed on all boxes, fittings, and similar enclosures to prevent accidental contact with energized parts or physical damage to parts or insulation. + +### 300.32 Conductors of Different Systems. + +See [[#300.3(C)(2) Over 1000 Volts, Nominal.|300.3(C)(2)]]. + +### 300.34 Conductor Bending Radius. + +The conductor shall not be bent to a radius less than 8 times the overall diameter for nonshielded conductors or 12 times the overall diameter for shielded or lead-covered conductors during or after installation. For multiconductor or multiplexed single-conductor cables having individually shielded conductors, the minimum bending radius is 12 times the diameter of the individually shielded conductors or +7 times the overall diameter, whichever is greater. + +### 300.35 Protection Against Induction Heating. + +Metallic raceways and associated conductors shall be arranged so as to avoid heating of the raceway in accordance with the applicable provisions of 300.20. + +### 300.37 Aboveground Wiring Methods. + +Aboveground conductors shall be installed in rigid metal conduit, in intermediate metal conduit, in electrical metallic tubing, in RTRC and PVC conduit, in cable trays, in auxiliary gutters, as busways, as cablebus, in other identified raceways, or as exposed runs of metal-clad cable suitable for the use and purpose. In locations accessible to qualified persons only, exposed runs of Type MV cables, bare conductors, and bare busbars shall also be permitted. Busbars shall be permitted to be either copper or aluminum. + +> [!important] Exception: +> Airfield lighting cable used in series circuits that are powered by regulators and installed in restricted airport lighting vaults shall be permitted as exposed cable installations. + +> [!info] Informational Note: +> FAA L-824 cables installed as exposed runs within a restricted vault area are common applications. + +### 300.38 Raceways in Wet Locations Above Grade. + +Where raceways are installed in wet locations above grade, the interior of these raceways shall be considered to be a wet location. + +Insulated conductors and cables installed in raceways in wet locations above grade shall comply with 310.10(C). + +### 300.39 Braid-Covered Insulated Conductors — Exposed Installation. + +Exposed runs of braid-covered insulated conductors shall have a flame-retardant braid. If the conductors used do not have this protection, a flame-retardant saturant shall be applied to the braid covering after installation. This treated braid covering shall be stripped back a safe distance at conductor terminals, according to the operating voltage. Where practicable, this distance shall not be less than 25 mm (1 in.) for each kilovolt of the conductor-to-ground voltage of the circuit. + +### 300.40 Insulation Shielding. + +Metallic and semiconducting insulation shielding components of shielded cables shall be removed for a distance dependent on the circuit voltage and insulation. Stress reduction means shall be provided at all terminations of factory-applied shielding. + +Metallic shielding components such as tapes, wires, or braids, or combinations thereof, shall be connected to an equipment grounding conductor, an equipment grounding busbar, or a grounding electrode. + +### 300.42 Moisture or Mechanical Protection for Metal-Sheathed Cables. + +Where cable conductors emerge from a metal sheath and where protection against moisture or physical damage is necessary, the insulation of the conductors shall be protected by a cable sheath terminating device. + +### 300.45 Danger Signs. + +Danger signs shall be conspicuously posted at points of access to conductors in all raceway systems and cable systems. The sign(s) shall meet the requirements in 110.21(B), shall be readily visible, and shall state the following: + +> DANGER—HIGH VOLTAGE—KEEP OUT + +### 300.50 Underground Installations. + +#### 300.50(A) General. + +Underground conductors shall be identified for the voltage and conditions under which they are installed. Direct-burial cables shall comply with the provisions of 310.10(E). Underground cables shall be installed in accordance with 300.50(A)(1), (A)(2), or (A)(3), and the installation shall meet the depth requirements of Table 300.50. + +Table 300.50 Minimum Cover Requirements + +General Conditions (not otherwise specified) Special Conditions (use if applicable) + +Column +1 + +Column +2 Column 3 Column 4 Column 5 Column 6 + +DirectBuriedCablesRTRC,PVC,andHDPEConduitRigid + +Metal + +Conduit and + +Intermediate + +Metal + +Conduit + +Raceways Under + +Buildings or Exterior + +Concrete Slabs, +100 mm (4 in.) + +Minimum + +Thickness + +Cables in Airport + +Runways or + +Adjacent Areas + +Where Trespass + +Is Prohibited + +Areas Subject to + +Vehicular Traffic, + +Such as + +Thoroughfares and + +Commercial Parking + +Areas + +Circuit + +Voltage mm in. mm in. mm in. mm in. mm in. mm in. a b c d + +General Conditions (not otherwise specified) Special Conditions (use if applicable) + +Column +1 + +Column +2 Column 3 Column 4 Column 5 Column 6 + +DirectBuriedCablesRTRC,PVC,andHDPEConduitRigid + +Metal + +Conduit and + +Intermediate + +Metal + +Conduit + +Raceways Under + +Buildings or Exterior + +Concrete Slabs, +100 mm (4 in.) + +Minimum + +Thickness + +Cables in Airport + +Runways or + +Adjacent Areas + +Where Trespass + +Is Prohibited + +Areas Subject to + +Vehicular Traffic, + +Such as + +Thoroughfares and + +Commercial Parking + +Areas + +Circuit + +Voltage mm in. mm in. mm in. mm in. mm in. mm in. + +Over +1000 V through +22 kV 750 30 450 18 150 6 100 4 450 18 600 24 + +Over 22 kV through +40 kV 900 36 600 24 150 6 100 4 450 18 600 24 + +Over 40 kV 1000 42 750 30 150 6 100 4 450 18 600 24 + +General Notes: +1. Lesser depths shall be permitted where cables and conductors rise for terminations or splices or where access is otherwise required. +2. Where solid rock prevents compliance with the cover depths specified in this table, the wiring shall be installed in a metal or nonmetallic raceway permitted for direct burial. The raceways shall be covered by a minimum of 50 mm (2 in.) of concrete extending down to rock. +3. In industrial establishments, where conditions of maintenance and supervision ensure that qualified persons will service the installation, the minimum cover requirements, for other than rigid metal conduit and intermediate metal conduit, shall be permitted to be reduced 150 mm (6 in.) for each 50 mm (2 in.) of concrete or equivalent placed entirely within the trench over the underground installation. + +Specific Footnotes: + +Cover is defined as the shortest distance in millimeters (inches) measured between a point on the top surface of any direct-buried conductor, cable, conduit, or other raceway and the top surface of finished grade, concrete, or similar cover. + +Underground direct-buried cables that are not encased or protected by concrete and are buried 750 mm (30 in.) or more below grade shall have their location identified by a warning ribbon that is placed in the trench at least 300 mm (12 in.) above the cables. + +Listed by a qualified testing agency as suitable for direct burial without encasement. All other nonmetallic systems shall require 50 mm +(2 in.) of concrete or equivalent above conduit in addition to the table depth. + +The slab shall extend a minimum of 150 mm (6 in.) beyond the underground installation, and a warning ribbon or other effective means suitable for the conditions shall be placed above the underground installation. + +##### 300.50(A)(1) Shielded Cables and Nonshielded Cables in Metal-Sheathed Cable Assemblies. + +Underground cables, including nonshielded, Type MC and moisture-impervious metal sheath cables, shall have those sheaths grounded through an effective grounding path meeting the requirements of 250.4(A)(5) or (B)(4). They shall be direct buried or installed in raceways identified for the use. + +##### 300.50(A)(2) Industrial Establishments. + +In industrial establishments, where conditions of maintenance and supervision ensure that only qualified persons service the installed cable, nonshielded single-conductor cables with insulation types up to 2000 volts that are listed for direct burial shall be permitted to be directly buried. b c d a b c d + +##### 300.50(A)(3) Other Nonshielded Cables. + +Other nonshielded cables not covered in 300.50(A)(1) or (A)(2) shall be installed in rigid metal conduit, intermediate metal conduit, or rigid nonmetallic conduit encased in not less than 75 mm (3 in.) of concrete. + +#### 300.50(B) Wet Locations. + +The interior of enclosures or raceways installed underground shall be considered to be a wet location. Insulated conductors and cables installed in these enclosures or raceways in underground installations shall be listed for use in wet locations and shall comply with +310.10(C). Any connections or splices in an underground installation shall be approved for wet locations. + +#### 300.50(C) Protection from Damage. + +Conductors emerging from the ground shall be enclosed in listed raceways. Raceways installed on poles shall be of rigid metal conduit, intermediate metal conduit, RTRC-XW, Schedule 80 PVC conduit, or equivalent, extending from the minimum cover depth specified in + +Table 300.50 to a point 2.5 m (8 ft) above finished grade. Conductors entering a building shall be protected by an approved enclosure or raceway from the minimum cover depth to the point of entrance. Where direct-buried conductors, raceways, or cables are subject to movement by settlement or frost, they shall be installed to prevent damage to the enclosed conductors or to the equipment connected to the raceways. Metallic enclosures shall be grounded. + +#### 300.50(D) Splices. + +Direct burial cables shall be permitted to be spliced or tapped without the use of splice boxes, provided they are installed using materials suitable for the application. The taps and splices shall be watertight and protected from mechanical damage. Where cables are shielded, the shielding shall be continuous across the splice or tap. + +> [!important] Exception: +> At splices of an engineered cabling system, metallic shields of direct-buried single-conductor cables with maintained spacing between phases shall be permitted to be interrupted and overlapped. Where shields are interrupted and overlapped, each shield section shall be grounded at one point. + +#### 300.50(E) Backfill. + +Backfill containing large rocks, paving materials, cinders, large or sharply angular substances, or corrosive materials shall not be placed in an excavation where materials can damage or contribute to the corrosion of raceways, cables, or other substructures or where it may prevent adequate compaction of fill. + +Protection in the form of granular or selected material or suitable sleeves shall be provided to prevent physical damage to the raceway or cable. + +#### 300.50(F) Raceway Seal. + +Where a raceway enters from an underground system, the end within the building shall be sealed with an identified compound so as to prevent the entrance of moisture or gases, or it shall be so arranged to prevent moisture from contacting live parts. diff --git a/nfpa-70_310_conductors_for_general_wiring.md b/nfpa-70_310_conductors_for_general_wiring.md index 344b99d..f3e2544 100644 --- a/nfpa-70_310_conductors_for_general_wiring.md +++ b/nfpa-70_310_conductors_for_general_wiring.md @@ -25,33 +25,168 @@ These requirements do not apply to conductors that form an integral part of equi such as motors, motor controllers, and similar equipment, or to conductors specifically provided for elsewhere in this Code. -Informational Note: -For flexible cords and cables, see Article 400. -For fixture wires, see Article 402. +> [!info] Informational Note: +> For flexible cords and cables, see Article 400. +> For fixture wires, see Article 402. - +### 310.3 Conductors. + +#### 310.3(A) Minimum Size of Conductors. + +The minimum size of conductors for voltage ratings up to and including 2000 volts shall be 14 AWG copper or 12 AWG aluminum or copper-clad aluminum, except as permitted elsewhere in this Code. + +#### 310.3(B) Conductor Material. + +Conductors in this article shall be of aluminum, copper-clad aluminum, or copper unless otherwise specified. + +Solid aluminum conductors 8, 10, and 12 AWG shall be made of an AA-8000 series electrical grade aluminum alloy conductor material. + +Stranded aluminum conductors 8 AWG through 1000 kcmil marked as Type RHH, RHW, XHHW, THW, THHW, THWN, THHN, service entrance + +Type SE Style U, and SE Style R shall be made of an AA-8000 series electrical grade aluminum alloy conductor material. + +#### 310.3(C) Stranded Conductors. + +Where installed in raceways, conductors 8 AWG and larger shall be stranded, unless specifically permitted or required elsewhere in this Code to be solid. + +#### 310.3(D) Insulated. + +Conductors not specifically permitted elsewhere in this Code to be covered or bare shall be insulated. + +> [!info] Informational Note: +> See 250.184 for insulation of neutral conductors of a solidly grounded high-voltage system. ## Part II. Construction Specifications ### 310.4 Conductor Constructions and Applications. -Insulated conductors shall comply with [[#Table 310.4(A) Conductor Applications and Insulations Rated 600 Volts|Table 310.4(A)]] -and [[#Table 310.4(B) Thickness of Insulation for Nonshielded Types RHH and RHW Solid Dielectric Insulated Conductors Rated 2000 Volts|Table 310.4(B)]]. +Insulated conductors shall comply with +[[#^t310-4a|Table 310.4(A)]] and +[[#^t310-4b|Table 310.4(B)]]. -Informational Note: -Thermoplastic insulation may stiffen at temperatures lower than −10°C (+14°F). -Thermoplastic insulation may also be deformed at normal temperatures -where subjected to pressure, such as at points of support. +> [!info] Informational Note: +> Thermoplastic insulation may stiffen at temperatures lower than −10°C (+14°F). +> Thermoplastic insulation may also be deformed at normal temperatures +> where subjected to pressure, such as at points of support. -### Table 310.4(A) Conductor Applications and Insulations Rated 600 Volts +#### Table 310.4(A) Conductor Applications and Insulations Rated 600 Volts ^t310-4a - +%% TABLE OMITTED %% -### Table 310.4(B) Thickness of Insulation for Nonshielded Types RHH and RHW Solid Dielectric Insulated Conductors Rated 2000 Volts +#### Table 310.4(B) Thickness of Insulation for Nonshielded Types RHH and RHW Solid Dielectric Insulated Conductors Rated 2000 Volts ^t310-4b - +%% TABLE OMITTED %% - +#### 310.6(A) Grounded Conductors. + +Insulated or covered grounded conductors shall be identified in accordance with 200.6. + +#### 310.6(B) Equipment Grounding Conductors. + +Equipment grounding conductors shall be identified in accordance with 250.119. + +#### 310.6(C) Ungrounded Conductors. + +Conductors that are intended for use as ungrounded conductors, whether used as a single conductor or in multiconductor cables, shall be finished to be clearly distinguishable from grounded and equipment grounding conductors. Distinguishing markings shall not conflict in any manner with the surface markings required by 310.8(B) (1). Branch-circuit ungrounded conductors shall be identified in accordance with 210.5(C). Feeders shall be identified in accordance with 215.12. + +> [!important] Exception: +> Conductor identification shall be permitted in accordance with 200.7. + +### 310.8 Marking. + +#### 310.8(A) Required Information. + +All conductors and cables shall be marked to indicate the following information, using the applicable method described in 310.8(B): + +* (1) The maximum rated voltage. + +* (2) The proper type letter or letters for the type of wire or cable as specified elsewhere in this Code. + +* (3) The manufacturer's name, trademark, or other distinctive marking by which the organization responsible for the product can be readily identified. + +* (4) The AWG size or circular mil area. + + > [!info] Informational Note: + > See Chapter 9, Table 8, Conductor Properties, + > for conductor area expressed in SI units + > for conductor sizes specified in AWG or circular mil area. + +* (5) Cable assemblies where the neutral conductor is smaller than the ungrounded conductors shall be so marked. + +#### 310.8(B) Method of Marking. + +##### 310.8(B)(1) Surface Marking. + +The following conductors and cables shall be durably marked on the surface: + +* (1) Single-conductor and multiconductor thermoset and thermoplastic-insulated wire and cable + +* (2) Nonmetallic-sheathed cable + +* (3) Service-entrance cable + +* (4) Underground feeder and branch-circuit cable + +* (5) Tray cable + +* (6) Irrigation cable + +* (7) Power-limited tray cable + +* (8) Instrumentation tray cable + +The AWG size or circular mil area shall be repeated at intervals not exceeding 610 mm (24 in.). All other markings shall be repeated at intervals not exceeding 1.0 m (40 in.). + +##### 310.8(B)(2) Marker Tape. + +Metal-covered multiconductor cables shall employ a marker tape located within the cable and running for its complete length. + +> [!important] Exception No. 1: +> Type MI cable shall not require a marker tape. + +> [!important] Exception No. 2: +> Type AC cable shall not require a marker tape. + +> [!important] Exception No. 3: +> The information required in 310.8(A) shall be permitted to be durably marked on the outer nonmetallic covering of Type MC, Type ITC, or Type PLTC cables at intervals not exceeding 1.0 m (40 in.). + +> [!important] Exception No. 4: +> The information required in 310.8(A) shall be permitted to be durably marked on a nonmetallic covering under the metallic sheath of Type ITC or Type PLTC cable at intervals not exceeding 1.0 m (40 in.). + +> [!info] Informational Note: +> Included in the group of metal-covered cables are Type AC cable (Article 320), Type MC cable (Article 330), and lead-sheathed cable. + +##### 310.8(B)(3) Tag Marking. + +The following conductors and cables shall be marked by means of a printed tag attached to the coil, reel, or carton: + +* (1) Type MI cable +* (2) Switchboard wires +* (3) Metal-covered, single-conductor cables +* (4) Type AC cable + +##### 310.8(B)(4) Optional Marking of Wire Size. + +The information required in 310.8(A)(4) shall be permitted to be marked on the surface of the individual insulated conductors for the following multiconductor cables: + +* (1) Type MC cable +* (2) Tray cable +* (3) Irrigation cable +* (4) Power-limited tray cable +* (5) Power-limited fire alarm cable +* (6) Instrumentation tray cable + +#### 310.8(C) Suffixes to Designate Number of Conductors. + +A type letter or letters used alone shall indicate a single insulated conductor. The letter suffixes shall be indicated as follows: + +* (1) D --- For two insulated conductors laid parallel within an outer nonmetallic covering + +* (2) M --- For an assembly of two or more insulated conductors twisted spirally within an outer nonmetallic covering + +#### 310.8(D) Optional Markings. + +All conductors and cables contained in Chapter 3 shall be permitted to be surface marked to indicate special characteristics of the cable materials. These markings include, but are not limited to, markings for limited smoke, sunlight resistant, and so forth. ## Part III. Installation @@ -62,7 +197,141 @@ shall be permitted for use in any of the wiring methods covered in Chapter 3 and as specified in their respective tables or as permitted elsewhere in this Code. - +#### 310.10(A) Dry Locations. + +Insulated conductors and cables used in dry locations shall be any of the types identified in this Code. + +#### 310.10(B) Dry and Damp Locations. + +Insulated conductors and cables used in dry and damp locations +shall be Types FEP, FEPB, MTW, PFA, RHH, RHW, RHW-2, +SA, THHN, THW, THW-2, THHW, THWN, THWN-2, TW, +XHH, XHHW, XHHW-2, XHHN, XHWN, XHWN-2, Z, or ZW. + +#### 310.10(C) Wet Locations. + +Insulated conductors and cables used in wet locations shall comply with one of the following: + +* (1) Be moisture-impervious metal-sheathed + +* (2) Be types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, + THWN, THWN-2, XHHW, XHHW-2, XHWN, XHWN-2 or ZW + +* (3) Be of a type listed for use in wet locations + +#### 310.10(D) Locations Exposed to Direct Sunlight. + +Insulated conductors or cables used where exposed to direct rays of the sun shall comply with (D)(1) or (D)(2): + +* (1) Conductors and cables shall be listed, or listed and marked, as being sunlight resistant + +* (2) Conductors and cables shall be covered with insulating material, such as tape or sleeving, that is listed, or listed and marked, as being sunlight resistant + +#### 310.10(E) Direct-Burial Conductors. + +Conductors used for direct-burial applications shall be of a type identified for such use. + +#### 310.10(F) Corrosive Conditions. + +Conductors exposed to oils, greases, vapors, gases, fumes, liquids, or other substances having a deleterious effect on the conductor or insulation shall be of a type suitable for the application. + +#### 310.10(G) Conductors in Parallel. + +##### 310.10(G)(1) General. + +Aluminum, copper-clad aluminum, or copper conductors for each phase, polarity, neutral, or grounded circuit shall be permitted to be connected in parallel (electrically joined at both ends) only in sizes 1/0 AWG and larger where installed in accordance with 310.10(G)(2) through (G) (6). + +> [!important] Exception No. 1: +> Conductors in sizes smaller than 1/0 AWG shall be permitted to be run in parallel to supply control power to indicating instruments, contactors, relays, solenoids, and similar control devices, or for frequencies of 360 Hz and higher, provided all of the following apply: + +* (1) They are contained within the same raceway or cable. + +* (2) The ampacity of each individual conductor is sufficient to carry the entire load current shared by the parallel conductors. + +* (3) The overcurrent protection is such that the ampacity of each individual conductor will not be exceeded if one or more of the parallel conductors become inadvertently disconnected. + +> [!important] Exception No. 2: +> Under engineering supervision, 2 AWG and 1 AWG grounded neutral conductors shall be permitted to be installed in parallel for existing installations. + +Informational Note to Exception No. 2: Exception No. 2 can be used to alleviate overheating of neutral conductors in existing installations due to high content of triplen harmonic currents. + +##### 310.10(G)(2) Conductor and Installation Characteristics. + +The paralleled conductors in each phase, polarity, neutral, grounded circuit conductor, equipment grounding conductor, or equipment bonding jumper shall comply with all of the following: + +* (1) Be the same length +* (2) Consist of the same conductor material +* (3) Be the same size in circular mil area +* (4) Have the same insulation type +* (5) Be terminated in the same manner + +##### 310.10(G)(3) Separate Cables or Raceways. + +Where run in separate cables or raceways, the cables or raceways with conductors shall have the same number of conductors and shall have the same electrical characteristics. Conductors of one phase, polarity, neutral, grounded circuit conductor, or equipment grounding conductor shall not be required to have the same physical characteristics as those of another phase, polarity, neutral, grounded circuit conductor, or equipment grounding conductor. + +##### 310.10(G)(4) Ampacity Adjustment. + +Conductors installed in parallel shall comply with the provisions of 310.15(C)(1). + +##### 310.10(G)(5) Equipment Grounding Conductors. + +Where parallel equipment grounding conductors are used, they shall be sized in accordance with 250.122. Sectioned equipment grounding conductors smaller than 1/0 AWG shall be permitted in multiconductor cables, if the combined circular mil area of the sectioned equipment grounding conductors in each cable complies with 250.122. + +##### 310.10(G)(6) Bonding Jumpers. + +Where parallel equipment bonding jumpers or supply-side bonding jumpers are installed in raceways, they shall be sized and installed in accordance with 250.102. + +### 310.12 Single-Phase Dwelling Services and Feeders. + +For one-family dwellings and the individual dwelling units of two-family and multifamily dwellings, service and feeder conductors supplied by a single-phase, 120/240-volt system shall be permitted to be sized in accordance with 310.12(A) through (D). + +For one-family dwellings and the individual dwelling units of two-family and multifamily dwellings, single-phase feeder conductors consisting of two ungrounded conductors and the neutral conductor from a 208Y/120 volt system shall be permitted to be sized in accordance with 310.12(A) through (C). + +#### 310.12(A) Services. + +For a service rated 100 amperes through 400 amperes, the service conductors supplying the entire load associated with a one-family dwelling, or the service conductors supplying the entire load associated with an individual dwelling unit in a two-family or multifamily dwelling, shall be permitted to have an ampacity not less than 83 percent of the service rating. If no adjustment or correction factors are required, Table 310.12 shall be permitted to be applied. + +#### 310.12(B) Feeders. + +For a feeder rated 100 amperes through 400 amperes, the feeder conductors supplying the entire load associated with a one-family dwelling, or the feeder conductors supplying the entire load associated with an individual dwelling unit in a two-family or multifamily dwelling, shall be permitted to have an ampacity not less than 83 percent of the feeder rating. If no adjustment or correction factors are required, Table 310.12 shall be permitted to be applied. + +#### 310.12(C) Feeder Ampacities. + +In no case shall a feeder for an individual dwelling unit be required to have an ampacity greater than that specified in 310.12(A) or (B). + +#### 310.12(D) Grounded Conductors. + +Grounded conductors shall be permitted to be sized smaller than the ungrounded conductors, if the requirements of 220.61 and 230.42 for service conductors or the requirements of 215.2 and 220.61 for feeder conductors are met. + +Where correction or adjustment factors are required by 310.15(B) or (C), they shall be permitted to be applied to the ampacity associated with the temperature rating of the conductor. + +> [!info] Informational Note No. 1: +> The service or feeder ratings addressed by this section are based on the standard ampere ratings for fuses and inverse time circuit breakers from 240.6(A). + +> [!info] Informational Note No. 2: +> See Example D7 in Annex D. + +#### Table 310.12 Single-Phase Dwelling Services and Feeders + +%% TODO: unpivot %% + +Conductor (AWG or kcmil) + +| Service or Feeder Rating (Amperes) | Copper | Aluminum or Copper-Clad Aluminum | +| ---------------------------------- | ------ | -------------------------------- | +| 100 | 4 | 2 | +| 110 | 3 | 1 | +| 125 | 2 | 1/0 | +| 150 | 1 | 2/0 | +| 175 | 1/0 | 3/0 | +| 200 | 2/0 | 4/0 | +| 225 | 3/0 | 250 | +| 250 | 4/0 | 300 | +| 300 | 250 | 350 | +| 350 | 350 | 500 | +| 400 | 400 | 600 | + +Note: If no adjustment or correction factors are required, this table shall be permitted to be applied. ### 310.14 Ampacities for Conductors Rated 0 Volts -- 2000 Volts. @@ -72,13 +341,71 @@ or as permitted elsewhere in this Code. Ampacities for conductors shall be permitted to be determined by tables as provided in 310.15 or under engineering supervision, as provided in 310.14(B). -Informational Note No. 1: -Ampacities provided by this section -do not take voltage drop into consideration. -See 210.19(A), Informational Note No. 4, for branch circuits -and 215.2(A), Informational Note No. 2, for feeders. +> [!info]Informational Note No. 1: +> Ampacities provided by this section +> do not take voltage drop into consideration. +> See 210.19(A), Informational Note No. 4, for branch circuits +> and 215.2(A), Informational Note No. 2, for feeders. - +> [!info] Informational Note No. 1: +> Ampacities provided by this section do not take voltage drop into consideration. See 210.19(A), Informational Note No. 4, for branch circuits and 215.2(A), Informational Note No. 2, for feeders. + +> [!info] Informational Note No. 2: +> For the allowable ampacities of Type MTW wire, see Table 12.5.1 in NFPA 79-2018, Electrical Standard for Industrial Machinery. + +##### 310.14(A)(2) Selection of Ampacity. + +Where more than one ampacity applies for a given circuit length, the lowest value shall be used. + +> [!important] Exception: +> Where different ampacities apply to portions of a circuit, the higher ampacity shall be permitted to be used if the total portion(s) of the circuit with lower ampacity does not exceed the lesser of 3.0 m (10 ft) or 10 percent of the total circuit. + +> [!info] Informational Note: +> See 110.14(C) for conductor temperature limitations due to termination provisions. + +##### 310.14(A)(3) Temperature Limitation of Conductors. + +No conductor shall be used in such a manner that its operating temperature exceeds that designated for the type of insulated conductor involved. In no case shall conductors be associated together in such a way, with respect to type of circuit, the wiring method employed, or the number of conductors, that the limiting temperature of any conductor is exceeded. + +> [!info] Informational Note No. 1: +> The temperature rating of a conductor \[see Table 310.4(A) and Table 311.10(A)\] is the maximum temperature, at any location along its length, that the conductor can withstand over a prolonged time period without serious degradation. The ampacity tables of Article 310 and the ampacity tables of Informative Annex B, the ambient temperature correction factors in 310.15(B), and the notes to the tables provide guidance for coordinating conductor sizes, types, ampacities, ambient temperatures, and number of associated conductors. The principal determinants of operating temperature are as follows: + +* (1) Ambient temperature --- + ambient temperature may vary along the conductor length as well as from time to time. + +* (2) Heat generated internally in the conductor + as the result of load current flow, + including fundamental and harmonic currents. + +* (3) The rate at which generated heat + dissipates into the ambient medium. + Thermal insulation that covers or surrounds conductors + affects the rate of heat dissipation. + +* (4) Adjacent load-carrying conductors --- + adjacent conductors have the dual effect + of raising the ambient temperature + and impeding heat dissipation. + +> [!info] Informational Note No. 2: +> Refer to 110.14(C) for the temperature limitation of terminations. + +#### 310.14(B) Engineering Supervision. + +Under engineering supervision, conductor ampacities shall be permitted to be calculated by means of Equation 310.14(B). + +##### Equation 310.14(B) + +$$ +I = \sqrt{ \frac{T_{c} - T_{a}}{R_{dc}(1+Y_{c})R_{ca}} } +$$ + +where: +* $T_{c}$ = conductor temperature in degrees Celsius (°C) +* $T_{a}$ = ambient temperature in degrees Celsius (°C) +* $R_{dc}$ = dc resistance of 305 mm (1 ft) of conductor in microohms at temperature, T +* $Y_{c}$ = component ac resistance resulting from skin effect and proximity effect +* $R_{ca}$ = effective thermal resistance between conductor and surrounding ambient ### 310.15 Ampacity Tables. @@ -99,36 +426,40 @@ if the corrected and adjusted ampacity does not exceed the ampacity for the temperature rating of the termination in accordance with the provisions of 110.14(C). -Informational Note No. 1: -Table 310.16 through Table 310.19 are application tables -for use in determining conductor sizes on loads -calculated in accordance with Part II, Part III, Part IV, or Part V of Article 220. -Ampacities result from consideration of one or more of the following: +> [!info] Informational Note No. 1: +> Table 310.16 through Table 310.19 are application tables +> for use in determining conductor sizes on loads +> calculated in accordance with Part II, Part III, Part IV, or Part V of Article 220. +> Ampacities result from consideration of one or more of the following: * (1) Temperature compatibility with connected equipment, especially the connection points. * (2) Coordination with circuit and system overcurrent protection. * (3) Compliance with the requirements of product listings or certifications. See 110.3(B). * (4) Preservation of the safety benefits of established industry practices and standardized procedures. -Informational Note No. 2: -For conductor area see Chapter 9, Table 8, Conductor Properties. -Interpolation is based on the conductor area -and not the conductor overall area. +> [!info] Informational Note No. 2: +> For conductor area see Chapter 9, Table 8, Conductor Properties. +> Interpolation is based on the conductor area +> and not the conductor overall area. - +%% Code terminology: **conductor area**, **conductor overall area** %% -Informational Note No. 3: -For the ampacities of flexible cords and cables, see 400.5. -For the ampacities of fixture wires, see 402.5. +> [!info] Informational Note No. 3: +> For the ampacities of flexible cords and cables, see 400.5. +> For the ampacities of fixture wires, see 402.5. -Informational Note No. 4: -For explanation of type letters used in tables -and for recognized sizes of conductors for the various conductor insulations, -see Table 310.4(A) and Table 310.4(B). -For installation requirements, -see 310.1 through 310.14 and the various articles of this Code. -For flexible cords, -see Table 400.4, Table 400.5(A)(1), and Table 400.5(A)(2). +> [!info] Informational Note No. 4: +> For explanation of type letters used in tables +> and for recognized sizes of conductors for the various conductor insulations, +> see Table 310.4(A) +> and Table 310.4(B). +> For installation requirements, +> see 310.1 through 310.14 +> and the various articles of this Code. +> For flexible cords, +> see Table 400.4, +> Table 400.5(A)(1), +> and Table 400.5(A)(2). #### 310.15(B) Ambient Temperature Correction Factors. @@ -139,35 +470,34 @@ other than those shown in the ampacity tables shall be corrected in accordance with Table 310.15(B)(1) or Table 310.15(B)(2), or shall be permitted to be calculated using Equation 310.15(B). - +##### Equation 310.15(B) $$ -I\prime = I \sqrt{\frac{ T_c -T_{a}\prime }{ T_c - T_a }} +I^{\prime} = I \sqrt{\frac{ T_{c} -T_{a}^{\prime} }{ T_{c} - T_a }} $$ where: * $I\prime$ = ampacity corrected for ambient temperature * $I$ = ampacity shown in the tables -* $T_c$ = temperature rating of conductor (°C) -* $T_{a}\prime$ = new ambient temperature (°C) +* $T_{c}$ = temperature rating of conductor (°C) +* $T_{a}^{\prime}$ = new ambient temperature (°C) * $T_a$ = ambient temperature used in the table (°C) ##### 310.15(B)(2) Rooftop. For raceways or cables exposed to direct sunlight on or above rooftops where the distance above the roof -to the bottom of the raceway or cable is less than 23 mm (7⁄8 in.), +to the bottom of the raceway or cable is less than 23 mm (7/8 in.), a temperature adder of 33°C (60°F) shall be added to the outdoor temperature to determine the applicable ambient temperature for application of the correction factors in Table 310.15(B)(1) or Table 310.15(B)(2). -Exception: -Type XHHW-2 insulated conductors shall not be subject to this ampacity adjustment. +> [!important] Exception: +> Type XHHW-2 insulated conductors shall not be subject to this ampacity adjustment. -Informational Note: -One source for the ambient temperatures in various locations -is the ASHRAE Handbook -- Fundamentals. +> [!info] Informational Note: +> One source for the ambient temperatures in various locations is the ASHRAE Handbook --- Fundamentals. ##### Table 310.15(B)(1) Ambient Temperature Correction Factors Based on 30°C (86°F) @@ -175,7 +505,7 @@ For ambient temperatures other than 30°C (86°F), multiply the ampacities specified in the ampacity tables by the appropriate correction factor shown below. - +%% TODO: TABLE OMITTED %% ##### Table 310.15(B)(2) Ambient Temperature Correction Factors Based on 40°C (104°F) @@ -183,7 +513,7 @@ For ambient temperatures other than 40°C (104°F), multiply the ampacities specified in the ampacity tables by the appropriate correction factor shown below. - +%% TODO: TABLE OMITTED %% #### 310.15(C) Adjustment Factors. @@ -196,17 +526,15 @@ are installed without maintaining spacing for a continuous length longer than 60 Each current-carrying conductor of a paralleled set of conductors shall be counted as a current-carrying conductor. - - ##### Table 310.15(C)(1) Adjustment Factors for More Than Three Current-Carrying Conductors | Number of Conductors* | Percent of Values in Table 310.16 Through Table 310.19 as Adjusted for Ambient Temperature if Necessary | | --------------------- | ------------------------------------------------------------------------------------------------------- | -| 4--6 | 80 | -| 7--9 | 70 | -| 10--20 | 50 | -| 21--30 | 45 | -| 31--40 | 40 | +| 4--6 | 80 | +| 7--9 | 70 | +| 10--20 | 50 | +| 21--30 | 45 | +| 31--40 | 40 | | 41 and above | 35 | \*Number of conductors is the total number of conductors in the raceway or cable, @@ -227,4 +555,119 @@ the temperature rating of the bare or covered conductor shall be equal to the lowest temperature rating of the insulated conductors for the purpose of determining ampacity. - +#### 310.15(E) Neutral Conductor. + +Neutral conductors shall be considered current carrying in accordance with any of the following: + +* (1) A neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted when applying the provisions of 310.15(C)(1). + +* (2) In a 3-wire circuit consisting of two phase conductors and the neutral conductor of a 4-wire, 3-phase, wye-connected system, a common conductor carries approximately the same current as the line-to-neutral load currents of the other conductors and shall be counted when applying the provisions of 310.15(C)(1). + +* (3) On a 4-wire, 3-phase wye circuit where the major portion of the load consists of nonlinear loads, harmonic currents are present in the neutral conductor; the neutral conductor shall therefore be considered a current-carrying conductor. + +#### 310.15(F) Grounding or Bonding Conductor. + +A grounding or bonding conductor shall not be counted when applying the provisions of 310.15(C)(1). + +### 310.16 Ampacities of Insulated Conductors in Raceway, Cable, or Earth (Directly Buried). + +The ampacities shall be as specified in Table 310.16 where all of the following conditions apply: + +* (1) Conductors are rated 0 volts through 2000 volts. + +* (2) Conductors are rated 60°C (140°F), 75°C (167°F), or 90°C (194°F). + +* (3) Wiring is installed in a 30°C (86°F) ambient temperature. + +* (4) There are not more than three current-carrying conductors. + +#### Table 310.16 Ampacities of Insulated Conductors with Not More Than Three Current-Carrying Conductors in Raceway, Cable, or Earth (Directly Buried) + +%% TODO: TABLE OMITTED %% + +Notes: +1. Section 310.15(B) shall be referenced for ampacity correction factors where the ambient temperature is other than 30°C (86°F). +2. Section 310.15(C)(1) shall be referenced for more than three current-carrying conductors. +3. Section 310.16 shall be referenced for conditions of use. + +\*Section 240.4(D) shall be referenced for conductor overcurrent protection limitations, except as modified elsewhere in the Code. + +### 310.17 Ampacities of Single-Insulated Conductors in Free Air. + +The ampacities shall be as specified in Table 310.17 where all of the following conditions apply: + +* (1) Conductors are rated 0 volts through 2000 volts. + +* (2) Conductors are rated 60°C (140°F), 75°C (167°F), or 90°C (194°F). + +* (3) Wiring is installed in a 30°C (86°F) ambient temperature. + +#### Table 310.17 Ampacities of Single-Insulated Conductors in Free Air + +%% TODO: TABLE OMITTED %% + +Notes: +1. Section 310.15(B) shall be referenced for ampacity correction factors where the ambient temperature is other than 30°C (86°F). +2. Section 310.17 shall be referenced for conditions of use. + +\*Section 240.4(D) shall be referenced for conductor overcurrent protection limitations, except as modified elsewhere in the Code. + +### 310.18 Ampacities of Insulated Conductors in Raceway or Cable. + +The ampacities shall be as specified in Table 310.18 where all of the following conditions apply: + +* (1) Conductors are rated 0 volts through 2000 volts. + +* (2) Conductors are rated 150°C (302°F), 200°C (392°F), or 250°C (482°F). + +* (3) Wiring is installed in a 40°C (104°F) ambient temperature. + +* (4) There are not more than three current-carrying conductors. + +#### Table 310.18 Ampacities of Insulated Conductors with Not More Than Three Current-Carrying Conductors in Raceway or Cable + +%% TODO: TABLE OMITTED %% + +### 310.19 Ampacities of Single-Insulated Conductors in Free Air. + +The ampacities shall be as specified in Table 310.19 where all of the following conditions apply: + +* (1) Conductors are rated 0 volts through 2000 volts. + +* (2) Conductors are rated up to 250°C (482°F). + +* (3) Wiring is installed in a 40°C (104°F) ambient temperature. + +#### Table 310.19 Ampacities of Single-Insulated Conductors in Free Air + +%% TODO: TABLE OMITTED %% + +### 310.20 Ampacities of Conductors Supported on a Messenger. + +The ampacities shall be as specified in Table 310.20 where all of the following conditions apply: + +* (1) Conductors are rated 0 volts through 2000 volts. +* (2) Conductors are rated 75°C (167°F) or 90°C (194°F). +* (3) Wiring is installed in a 40°C (104°F) ambient temperature. +* (4) There are not more than three single-insulated conductors. + +#### Table 310.20 Ampacities of Conductors on a Messenger + +%% TODO: TABLE OMITTED %% + +Notes: +1. Section 310.15(B) shall be referenced for ampacity correction factors where the ambient temperature is other than 40°C (104°F). +2. Section 310.15(C)(1) shall be referenced for more than three current-carrying conductors. +3. Section 310.20 shall be referenced for conditions of use. + +### 310.21 Ampacities of Bare or Covered Conductors in Free Air. + +The ampacities shall be as specified in Table 310.21 where all of the following conditions apply: + +* (1) Wind velocity is 610 mm/sec (2 ft/sec). +* (2) Conductors are 80°C (176°F) total conductor temperature. +* (3) Wiring is installed in a 40°C (104°F) ambient temperature. + +#### Table 310.21 Ampacities of Bare or Covered Conductors in Free Air + +%% TODO: TABLE OMITTED %% diff --git a/nfpa-70_311_mv-conductors.md b/nfpa-70_311_mv-conductors.md new file mode 100644 index 0000000..8b7dc7f --- /dev/null +++ b/nfpa-70_311_mv-conductors.md @@ -0,0 +1,1993 @@ +--- +id: +aliases: + - nec-311 +tags: + - authorship/other + - destiny/uncertain + - exclude-from-word-count + - status/draft + - topic/construction/electrical + - type/media +title: Article 311 Medium Voltage Conductors and Cable +--- +# Article 311 Medium Voltage Conductors and Cable + +## Part I. General + +### 311.1 Scope. + +This article covers the use, installation, construction specifications, and ampacities for Type MV medium voltage conductors and cable. + +### 311.2 Definitions. + +The definitions in this section shall apply within this article and throughout the Code. + +Electrical Ducts. + +Electrical conduits, or other raceways round in cross section, that are suitable for use underground or embedded in concrete. + +Medium Voltage Cable, Type MV. + +A single or multiconductor solid dielectric insulated cable rated 2001 volts up to and including 35,000 volts, nominal. + +Thermal Resistivity. + +As used in this Code, the heat transfer capability through a substance by conduction. + +> [!info] Informational Note: +> Thermal resistivity is the reciprocal of thermal conductivity and is designated Rho, which is expressed in the units +°C-cm/W. + +### 311.6 Listing Requirements. + +Type MV cables and associated fittings shall be listed. + +## Part II. Construction Specifications + +### 311.10 Constructions and Applications. + +Type MV cables shall comply with the applicable provisions in 311.10(A) through (C). + +#### 311.10(A) Conductor Application and Insulation. + +Conductor application and insulation shall comply with Table 311.10(A). + +#### 311.10(B) Thickness of Insulation and Jacket for Nonshielded Insulated Conductors. + +Thickness of insulation and jacket for nonshielded solid dielectric insulated conductors rated 2001 volts to 5000 volts shall comply with + +Table 311.10(B). + +#### 311.10(C) Thickness of Insulation for Shielded Insulated Conductors. + +Thickness of insulation for shielded solid dielectric insulated conductors rated 2001 volts to 35,000 volts shall comply with Table +311.10(C) and 311.10(C)(1) through (C)(3). + +##### 311.10(C)(1) 100 Percent Insulation Level. + +Cables shall be permitted to be applied where the system is provided with relay protection such that ground faults will be cleared as rapidly as possible but, in any case, within 1 minute. These cables are applicable to cable installations that are on grounded systems and shall be permitted to be used on other systems provided the above clearing requirements are met in completely de-energizing the faulted section. + +##### 311.10(C)(2) 133 Percent Insulation Level. + +Cables shall be permitted to be applied in situations where the clearing time requirements of the 100 percent level category cannot be met and the faulted section will be de-energized in a time not exceeding 1 hour. Cable shall be permitted to be used in 100 percent insulation level applications where the installation requires additional insulation. + +##### 311.10(C)(3) 173 Percent Insulation Level. + +Cables shall be permitted to be applied under all of the following conditions: + +* (1) In industrial establishments where the conditions of maintenance and supervision ensure only qualified persons service the installation + +* (2) Where the fault clearing time requirements of the 133 percent level category cannot be met + +* (3) Where an orderly shutdown is required to protect equipment and personnel + +* (4) Where the faulted section will be de-energized in an orderly shutdown + +Cables shall be permitted to be used in 100 percent or 133 percent insulation level applications where the installation requires additional insulation. + +Table 311.10(A) Conductor Application and Insulation Rated 2001 Volts and Higher + +Trade + +Name + +Type + +Letter + +Maximum Operating + +Temperature + +Application + +Provision Insulation + +Outer + +Covering + +Medium voltage solid dielectric + +MV-90 90°C Dry or wet locations Thermoplastic or thermosetting + +Jacket, sheath, or armor + +MV-105* 105°C +*Where design conditions require maximum conductor temperatures above 90°C. + +Table 311.10(B) Thickness of Insulation and Jacket for Nonshielded Solid Dielectric Insulated Conductors + +Rated 2001 Volts to 5000 Volts + +Conductor + +Size +(AWG or kcmil) + +Dry Locations, Single Conductor Wet or Dry Locations + +Without Jacket + +Insulation + +With Jacket Single Conductor Multiconductor + +Insulation* + +Insulation Jacket Insulation Jacket mm mils mm mils mm mils mm mils mm mils mm mils +8 2.79 110 2.29 90 0.76 30 3.18 125 2.03 80 2.29 90 +6 2.79 110 2.29 90 0.76 30 3.18 125 2.03 80 2.29 90 +4–2 2.79 110 2.29 90 1.14 45 3.18 125 2.03 80 2.29 90 + +Conductor + +Size +(AWG or kcmil) + +Dry Locations, Single Conductor Wet or Dry Locations + +Without Jacket + +Insulation + +With Jacket Single Conductor Multiconductor + +Insulation* + +Insulation Jacket Insulation Jacket mm mils mm mils mm mils mm mils mm mils mm mils +1–2/0 2.79 110 2.29 90 1.14 45 3.18 125 2.03 80 2.29 90 +3/0–4/0 2.79 110 2.29 90 1.65 65 3.18 125 2.41 95 2.29 90 +213–500 3.05 120 2.29 90 1.65 65 3.56 140 2.79 110 2.29 90 +501–750 3.30 130 2.29 90 1.65 65 3.94 155 3.18 125 2.29 90 +751–1000 3.30 130 2.29 90 1.65 65 3.94 155 3.18 125 2.29 90 +1001–1250 3.56 140 2.92 115 1.65 65 4.32 170 3.56 140 2.92 115 +1251–1500 3.56 140 2.92 115 2.03 80 4.32 170 3.56 140 2.92 115 +1501–2000 3.56 140 2.92 115 2.03 80 4.32 170 3.94 155 3.56 140 +*Under a common overall covering such as a jacket, sheath, or armor. + +Conductor + +Size +(AWG or kcmil) +25,001–28,000 Volts 28,001–35,000 Volts +100 + +Percent + +Insulation + +Level +133 + +Percent + +Insulation + +Level +173 + +Percent + +Insulation + +Level +100 + +Percent + +Insulation + +Level +133 + +Percent + +Insulation + +Level +173 + +Percent + +Insulation + +Level mm mils mm mils mm mils mm mils mm mils mm mils +1 7.11 280 8.76 345 11.30 445 — — — — — — +1/0–2000 7.11 280 8.76 345 11.30 445 8.76 345 10.67 420 14.73 580 + +### 311.12 Conductors. + +Table 311.10(C) Thickness of Insulation for Shielded Solid Dielectric Insulated Conductors Rated 2001 Vol +2001– +5000 + +Volts 5001–8000 Volts 8001–15,000 Volts + +Conductor + +Size +(AWG or kcmil) +100 + +Percent + +Insulation + +Level +100 + +Percent + +Insulation + +Level +133 + +Percent + +Insulation + +Level +173 + +Percent + +Insulation + +Level +100 + +Percent + +Insulation + +Level +133 + +Percent + +Insulation + +Level +173 + +Percent + +Insulation + +Level +100 + +Percen + +Insulat + +Leve mm mils mm mils mm mils mm mils mm mils mm mils mm mils mm m +8 2.29 90 — — — — — — — — — — — — — — +6–4 2.29 90 2.92 115 3.56 140 4.45 175 — — — — — — — — +2 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 — — +1 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 2 +1/0–2000 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 2 + +#### 311.12(A) Minimum Size of Conductors. + +The minimum size of conductors shall be as shown in Table 311.12(A), except as permitted elsewhere in this Code. + +Table 311.12(A) Minimum Size of Conductors + +Conductor Voltage Rating (Volts) + +Minimum Conductor Size (AWG) + +Copper, Aluminum, or Copper-Clad Aluminum +2001–5000 8 +5001–8000 6 +8001–15,000 2 +15,001–28,000 1 +28,001–35,000 1/0 + +#### 311.12(B) Conductor Material. + +Conductors shall be of aluminum, copper-clad aluminum, or copper unless otherwise specified. + +#### 311.12(C) Stranded Conductors. + +Where installed in raceways, conductors not specifically permitted or required elsewhere in this Code to be solid shall be stranded. + +### 311.14 Conductor Identification. + +Conductors that are intended for use as ungrounded conductors, whether used as a single conductor or in multiconductor cables, shall be finished to be clearly distinguishable from grounded and grounding conductors. Distinguishing markings shall not conflict in any manner with the surface markings required by 311.16(B)(1). Branch-circuit ungrounded conductors shall be identified in accordance with 210.5(C). Feeders shall be identified in accordance with 215.12. + +### 311.16 Marking. + +#### 311.16(A) Required Information. + +All conductors and cables shall be marked to indicate the following information, using the applicable method described in 311.16(B): + +* (1) The maximum rated voltage + +* (2) The proper type letter or letters for the type of wire or cable as specified elsewhere in this Code + +* (3) The manufacturer’s name, trademark, or other distinctive marking by which the organization responsible for the product can be readily identified + +* (4) The AWG size or circular mil area + +> [!info] Informational Note: +> See Chapter 9, Table 8, Conductor Properties, for conductor area expressed in SI units for conductor sizes specified in AWG or circular mil area. + +#### 311.16(B) Method of Marking. + +One or more of the methods in 311.16(B)(1) through (B)(4) shall be used for marking of cable. + +##### 311.16(B)(1) Surface Marking. + +Cables shall be durably marked on the surface. The AWG size or circular mil area shall be repeated at intervals not exceeding 610 mm +(24 in.). All other markings shall be repeated at intervals not exceeding 1.0 m (40 in.). + +##### 311.16(B)(2) Marker Tape. + +Metal-covered multiconductor cables shall employ a marker tape located within the cable and along its complete length. + +##### 311.16(B)(3) Tag Marking. + +Metal-covered, single-conductor cables shall be marked by means of a printed tag attached to the reel. + +##### 311.16(B)(4) Optional Marking of Wire Size. + +The information required in 311.16(A)(4) shall be permitted to be marked on the surface of the individual insulated conductors for multiconductor Type MC cable. + +#### 311.16(C) Optional Markings. + +Cables shall be permitted to be marked to indicate special characteristics of the cable materials, such as limited smoke and sunlight resistance. + +## Part III. Installation + +### 311.30 Installation. + +Type MV cable shall be installed, terminated, and tested by qualified persons. + +> [!info] Informational Note No. 1: +> Information about accepted industry practices and installation procedures for medium-voltage cable are described in ANSI/NECA/NCSCB 600, Standard for Installing and Maintaining Medium-Voltage Cable, and in IEEE 576, Recommended + +Practice for Installation, Termination, and Testing of Insulated Power Cables as Used in Industrial and Commercial Applications. + +> [!info] Informational Note No. 2: +> Where medium-voltage cable is used for dc circuits, low frequency polarization can create hazardous voltages. When handling the cable these voltages may be present or may develop on dc stressed cable while the circuit is energized. + +Solidly grounding the cable prior to contacting, cutting or disconnecting cables in dc circuits is a method to discharge these voltages. + +### 311.32 Uses Permitted. + +Type MV cable shall be permitted for use on power systems rated up to and including 35,000 volts, nominal, as follows: + +* (1) In wet or dry locations. + +* (2) In raceways. + +* (3) In cable trays, where identified for the use, in accordance with 392.10, 392.20(B), (C), and (D), 392.22(C), 392.30(B)(1), 392.46, +392.56, and 392.60. Type MV cable that has an overall metallic sheath or armor, complies with the requirements for Type MC cable, and is identified as “MV or MC” shall be permitted to be installed in cable trays in accordance with 392.10(B)(2). + +* (4) In messenger-supported wiring in accordance with Part II of Article 396. + +* (5) As exposed runs in accordance with 300.37. Type MV cable that has an overall metallic sheath or armor, complies with the requirements for Type MC cable, and is identified as “MV or MC” shall be permitted to be installed as exposed runs of metal-clad cable in accordance with 300.37. + +* (6) Corrosive conditions where exposed to oils, greases, vapors, gases, fumes, liquids, or other substances having a deleterious effect on the conductor or insulation shall be of a type suitable for the application. + +* (7) Conductors in parallel in accordance with 310.10(G). + +* (8) Type MV cable used where exposed to direct sunlight shall be identified for the use. + +> [!info] Informational Note: +> The “uses permitted” is not an all-inclusive list. + +### 311.36 Direct-Burial Conductors. + +Type MV conductors and cables used for direct burial applications shall be shielded, identified for such use, and installed in accordance with 300.50. + +> [!important] Exception No. 1: +> Nonshielded multiconductor cables rated 2001 volts to 2400 volts shall be permitted if the cable has an overall metallic sheath or armor. + +The metallic shield, sheath, or armor shall be connected to a grounding electrode conductor, a grounding busbar, or a grounding electrode. + +> [!important] Exception No. 2: +> Airfield lighting cable used in series circuits that are rated up to 5000 volts and are powered by regulators shall be permitted to be nonshielded. + +Informational Note to Exception No. 2: Federal Aviation Administration (FAA) Advisory Circulars (ACs) provide additional practices and methods for airport lighting. + +### 311.40 Support. + +Type MV cable terminated in equipment or installed in pull boxes or vaults shall be secured and supported by metallic or nonmetallic supports suitable to withstand the weight by cable ties listed and identified for securement and support, or other approved means, at intervals not exceeding 1.5 m (5 ft) from terminations or a maximum of 1.8 m (6 ft) between supports. + +### 311.44 Shielding. + +Nonshielded, ozone-resistant insulated conductors with a maximum phase-to-phase voltage of 5000 volts shall be permitted in Type + +MC cables in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation. For other establishments, solid dielectric insulated conductors operated above 2000 volts in permanent installations shall have ozone-resistant insulation and shall be shielded. All metallic insulation shields shall be connected to a grounding electrode conductor, a grounding busbar, an equipment grounding conductor, or a grounding electrode. +\[311.60(B)\] + +T = + +T = +ΔT = + +R = + +Y = + +R = + +> [!info] Informational Note: +> The primary purposes of shielding are to confine the voltage stresses to the insulation, dissipate insulation leakage current, drain off the capacitive charging current, and carry ground-fault current to facilitate operation of ground-fault protective devices in the event of an electrical cable fault. + +> [!important] Exception No. 1: +> Nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use up to 2400 volts under the following conditions: + +* (1) Conductors shall have insulation resistant to electric discharge and surface tracking, or the insulated conductor(s) shall be covered with a material resistant to ozone, electric discharge, and surface tracking. + +* (2) Where used in wet locations, the insulated conductor(s) shall have an overall nonmetallic jacket or a continuous metallic sheath. + +* (3) Insulation and jacket thicknesses shall be in accordance with Table 311.10(B). + +> [!important] Exception No. 2: +> Nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use up to 5000 volts to replace existing nonshielded conductors, on existing equipment in industrial establishments only, under the following conditions: + +* (1) Where the condition of maintenance and supervision ensures that only qualified personnel install and service the installation. + +* (2) Conductors shall have insulation resistant to electric discharge and surface tracking, or the insulated conductor(s) shall be covered with a material resistant to ozone, electric discharge, and surface tracking. + +* (3) Where used in wet locations, the insulated conductor(s) shall have an overall nonmetallic jacket or a continuous metallic sheath. + +* (4) Insulation and jacket thicknesses shall be in accordance with Table 311.10(B). + +> [!info] Informational Note: +> Relocation or replacement of equipment may not comply with the term existing as related to this exception. + +> [!important] Exception No. 3: +> Where permitted in 311.36, Exception No. 2. + +## Part IV. Ampacities + +### 311.60 Ampacities of Conductors. + +#### 311.60(A) General. + +##### 311.60(A)(1) Tables or Engineering Supervision. + +Ampacities for solid dielectric-insulated conductors shall be permitted to be determined by tables or under engineering supervision, as provided in 311.60(B) and (C). + +The ampacity of Type MV cable installed in cable tray shall be determined in accordance with 392.80(B). + +##### 311.60(A)(2) Selection of Ampacity. + +Where more than one calculated or tabulated ampacity could apply for a given circuit length, the lowest value shall be used. + +> [!important] Exception: +> Where different ampacities apply to portions of a circuit, the higher ampacity shall be permitted to be used if the total portion(s) of the circuit with the lower ampacity does not exceed the lesser of 3.0 m (10 ft) or 10 percent of the total circuit. + +> [!info] Informational Note: +> See 110.40 for conductor temperature limitations due to termination provisions. + +#### 311.60(B) Engineering Supervision. + +Under engineering supervision, conductor ampacities shall be permitted to be calculated by using the following general equation: where: conductor temperature (°C) ambient temperature (°C) dielectric loss temperature rise dc resistance of conductor at temperature, T component ac resistance resulting from skin effect and proximity effect effective thermal resistance between conductor and surrounding ambient c a d dc c c ca + +> [!info] Informational Note: +> The dielectric loss temperature rise (ΔT ) is negligible for single circuit extruded dielectric cables rated below 46 kilovolts. + +#### 311.60(C) Tables. + +Ampacities for conductors rated 2001 volts to 35,000 volts shall be as specified in Table 311.60(C)(67) through Table 311.60(C)(86). + +Ampacities for ambient temperatures other than those specified in the ampacity tables shall be corrected in accordance with 311.60(D) +(4). + +> [!info] Informational Note No. 1: +> For ampacities calculated in accordance with 311.60(A), reference IEEE 835, Standard Power Cable + +Ampacity Tables, and the references therein for availability of all factors and constants. + +> [!info] Informational Note No. 2: +> Ampacities provided by this section do not take voltage drop into consideration. See 210.19(A), Informational + +Note No. 4, for branch circuits and 215.2(A), Informational Note No. 2, for feeders. + +Table 311.60(C)(67) Ampacities of Insulated Single Copper Conductor Cables Triplexed in Air + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +8 65 74 — — +6 90 99 100 110 +4 120 130 130 140 +2 160 175 170 195 +1 185 205 195 225 +1/0 215 240 225 255 +2/0 250 275 260 295 +3/0 290 320 300 340 +4/0 335 375 345 390 +250 375 415 380 430 +350 465 515 470 525 +500 580 645 580 650 +750 750 835 730 820 +1000 880 980 850 950 + +Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and +311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F). + +Table 311.60(C)(68) Ampacities of Insulated Single Aluminum Conductor Cables Triplexed in Air + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +8 50 57 — — +6 70 77 75 84 +4 90 100 100 110 +2 125 135 130 150 +1 145 160 150 175 +1/0 170 185 175 200 d + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +2/0 195 215 200 230 +3/0 225 250 230 265 +4/0 265 290 270 305 +250 295 325 300 335 +350 365 405 370 415 +500 460 510 460 515 +750 600 665 590 660 +1000 715 800 700 780 + +Note: Refer to 311.60(E) for basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and +311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F). + +Table 311.60(C)(69) Ampacities of Insulated Single Copper Conductor Isolated in Air + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–15,000 Volts Ampacity +15,001–35,000 Volts + +Ampacity +90°C (194°F) + +Type MV-90 +105°C (221°F) + +Type MV-105 +90°C (194°F) + +Type MV-90 +105°C (221°F) + +Type MV-105 +90°C (194°F) + +Type MV-90 +105°C (221°F) + +Type MV-105 +8 83 93 — — — — +6 110 120 110 125 — — +4 145 160 150 165 — — +2 190 215 195 215 — — +1 225 250 225 250 225 250 +1/0 260 290 260 290 260 290 +2/0 300 330 300 335 300 330 +3/0 345 385 345 385 345 380 +4/0 400 445 400 445 395 445 +250 445 495 445 495 440 490 +350 550 615 550 610 545 605 +500 695 775 685 765 680 755 +750 900 1000 885 990 870 970 +1000 1075 1200 1060 1185 1040 1160 +1250 1230 1370 1210 1350 1185 1320 +1500 1365 1525 1345 1500 1315 1465 +1750 1495 1665 1470 1640 1430 1595 +2000 1605 1790 1575 1755 1535 1710 + +Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and +311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F). + +Table 311.60(C)(70) Ampacities of Insulated Single Aluminum Conductor Isolated in Air + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–15,000 Volts Ampacity +15,001–35,000 Volts + +Ampacity +90°C (194°F) + +Type MV-90 +105°C (221°F) + +Type MV-105 +90°C (194°F) + +Type MV-90 +105°C (221°F) + +Type MV-105 +90°C (194°F) + +Type MV-90 +105°C (221°F) + +Type MV-105 +8 64 71 — — — — +6 85 95 87 97 — — +4 115 125 115 130 — — +2 150 165 150 170 — — +1 175 195 175 195 175 195 +1/0 200 225 200 225 200 225 +2/0 230 260 235 260 230 260 +3/0 270 300 270 300 270 300 +4/0 310 350 310 350 310 345 +250 345 385 345 385 345 380 +350 430 480 430 480 430 475 +500 545 605 535 600 530 590 +750 710 790 700 780 685 765 +1000 855 950 840 940 825 920 +1250 980 1095 970 1080 950 1055 +1500 1105 1230 1085 1215 1060 1180 +1750 1215 1355 1195 1335 1165 1300 +2000 1320 1475 1295 1445 1265 1410 + +Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and +311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F). + +Table 311.60(C)(71) Ampacities of an Insulated + +Three-Conductor Copper Cable Isolated in Air + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +8 59 66 — — +6 79 88 93 105 +4 105 115 120 135 +2 140 154 165 185 +1 160 180 185 210 +1/0 185 205 215 240 +2/0 215 240 245 275 +3/0 250 280 285 315 +4/0 285 320 325 360 +250 320 355 360 400 +350 395 440 435 490 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +500 485 545 535 600 +750 615 685 670 745 +1000 705 790 770 860 + +Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and +311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F). + +Table 311.60(C)(72) Ampacities of an Insulated + +Three-Conductor Aluminum Cable Isolated in Air + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +8 46 51 — — +6 61 68 72 80 +4 81 90 95 105 +2 110 120 125 145 +1 125 140 145 165 +1/0 145 160 170 185 +2/0 170 185 190 215 +3/0 195 215 220 245 +4/0 225 250 255 285 +250 250 280 280 315 +350 310 345 345 385 +500 385 430 425 475 +750 495 550 540 600 +1000 585 650 635 705 + +Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and +311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F). + +Table 311.60(C)(73) Ampacities of an Insulated Triplexed or Three Single-Conductor Copper Cables in + +Isolated Conduit in Air + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +8 55 61 — — +6 75 84 83 93 +4 97 110 110 120 +2 130 145 150 165 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +1 155 175 170 190 +1/0 180 200 195 215 +2/0 205 225 225 255 +3/0 240 270 260 290 +4/0 280 305 295 330 +250 315 355 330 365 +350 385 430 395 440 +500 475 530 480 535 +750 600 665 585 655 +1000 690 770 675 755 + +Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and +311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F). + +Table 311.60(C)(74) Ampacities of an Insulated Triplexed or Three Single-Conductor Aluminum Cables in + +Isolated Conduit in Air + +Conductor Size (AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +8 43 48 — — +6 58 65 65 72 +4 76 85 84 94 +2 100 115 115 130 +1 120 135 130 150 +1/0 140 155 150 170 +2/0 160 175 175 200 +3/0 190 210 200 225 +4/0 215 240 230 260 +250 250 280 255 290 +350 305 340 310 350 +500 380 425 385 430 +750 490 545 485 540 +1000 580 645 565 640 + +Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and +311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F). + +Table 311.60(C)(75) Ampacities of an Insulated + +Three-Conductor Copper Cable in Isolated Conduit in Air + +Conductor Temperature Rating of Conductor + +Size +(AWG or kcmil) +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +8 52 58 — — +6 69 77 83 92 +4 91 100 105 120 +2 125 135 145 165 +1 140 155 165 185 +1/0 165 185 195 215 +2/0 190 210 220 245 +3/0 220 245 250 280 +4/0 255 285 290 320 +250 280 315 315 350 +350 350 390 385 430 +500 425 475 470 525 +750 525 585 570 635 +1000 590 660 650 725 + +Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and +311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F). + +Table 311.60(C)(76) Ampacities of an Insulated + +Three-Conductor Aluminum Cable in Isolated Conduit in Air + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +8 41 46 — — +6 53 59 64 71 +4 71 79 84 94 +2 96 105 115 125 +1 110 125 130 145 +1/0 130 145 150 170 +2/0 150 165 170 190 +3/0 170 190 195 220 +4/0 200 225 225 255 +250 220 245 250 280 +350 275 305 305 340 +500 340 380 380 425 +750 430 480 470 520 +1000 505 560 550 615 + +Note: Refer to 311.60(E) for the basis of ampacities, 311.10(A) for conductor maximum operating temperature and application, and +311.60(D)(4) for the ampacity correction factors where the ambient air temperature is other than 40°C (104°F). + +Table 311.60(C)(77) Ampacities of Three Single-Insulated Copper Conductors in Underground Electrical + +Ducts +(Three Conductors per Electrical Duct) + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV90105°C +(221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +One Circuit \[See Figure 311.60(D)(3), + +Detail 1.\] +8 64 69 — — +6 85 92 90 97 +4 110 120 115 125 +2 145 155 155 165 +1 170 180 175 185 +1/0 195 210 200 215 +2/0 220 235 230 245 +3/0 250 270 260 275 +4/0 290 310 295 315 +250 320 345 325 345 +350 385 415 390 415 +500 470 505 465 500 +750 585 630 565 610 +1000 670 720 640 690 + +Three Circuits \[See Figure 311.60(D)(3), + +Detail 2.\] +8 56 60 — — +6 73 79 77 83 +4 95 100 99 105 +2 125 130 130 135 +1 140 150 145 155 +1/0 160 175 165 175 +2/0 185 195 185 200 +3/0 210 225 210 225 +4/0 235 255 240 255 +250 260 280 260 280 +350 315 335 310 330 +500 375 405 370 395 +750 460 495 440 475 +1000 525 565 495 535 + +Six Circuits \[See Figure 311.60(D)(3), + +Detail 3.\] + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV90105°C +(221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +8 48 52 — — +6 62 67 64 68 +4 80 86 82 88 +2 105 110 105 115 +1 115 125 120 125 +1/0 135 145 135 145 +2/0 150 160 150 165 +3/0 170 185 170 185 +4/0 195 210 190 205 +250 210 225 210 225 +350 250 270 245 265 +500 300 325 290 310 +750 365 395 350 375 +1000 410 445 390 415 + +Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor. + +Table 311.60(C)(78) Ampacities of Three Single-Insulated Aluminum Conductors in Underground + +Electrical Ducts +(Three Conductors per Electrical Duct) + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV90105°C +(221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +One Circuit \[See Figure 311.60(D)(3), + +Detail 1.\] +8 50 54 — — +6 66 71 70 75 +4 86 93 91 98 +2 115 125 120 130 +1 130 140 135 145 +1/0 150 160 155 165 +2/0 170 185 175 190 +3/0 195 210 200 215 +4/0 225 245 230 245 +250 250 270 250 270 +350 305 325 305 330 +500 370 400 370 400 +750 470 505 455 490 +1000 545 590 525 565 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV90105°C +(221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +Three Circuits \[See Figure 311.60(D)(3), + +Detail 2.\] +8 44 47 — — +6 57 61 60 65 +4 74 80 77 83 +2 96 105 100 105 +1 110 120 110 120 +1/0 125 135 125 140 +2/0 145 155 145 155 +3/0 160 175 165 175 +4/0 185 200 185 200 +250 205 220 200 220 +350 245 265 245 260 +500 295 320 290 315 +750 370 395 355 385 +1000 425 460 405 440 + +Six Circuits \[See Figure 311.60(D)(3), + +Detail 3.\] +8 38 41 — — +6 48 52 50 54 +4 62 67 64 69 +2 80 86 80 88 +1 91 98 90 99 +1/0 105 110 105 110 +2/0 115 125 115 125 +3/0 135 145 130 145 +4/0 150 165 150 160 +250 165 180 165 175 +350 195 210 195 210 +500 240 255 230 250 +750 290 315 280 305 +1000 335 360 320 345 + +Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor. + +Table 311.60(C)(79) Ampacities of Three Insulated Copper Conductors Cabled Within an Overall Covering +(Three-Conductor Cable) in Underground Electrical Ducts (One Cable per Electrical Duct) + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV90105°C +(221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV90105°C +(221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +One Circuit \[See Figure 311.60(D)(3), + +Detail 1.\] +8 59 64 — — +6 78 84 88 95 +4 100 110 115 125 +2 135 145 150 160 +1 155 165 170 185 +1/0 175 190 195 210 +2/0 200 220 220 235 +3/0 230 250 250 270 +4/0 265 285 285 305 +250 290 315 310 335 +350 355 380 375 400 +500 430 460 450 485 +750 530 570 545 585 +1000 600 645 615 660 + +Three Circuits \[See Figure 311.60(D)(3), + +Detail 2.\] +8 53 57 — — +6 69 74 75 81 +4 89 96 97 105 +2 115 125 125 135 +1 135 145 140 155 +1/0 150 165 160 175 +2/0 170 185 185 195 +3/0 195 210 205 220 +4/0 225 240 230 250 +250 245 265 255 270 +350 295 315 305 325 +500 355 380 360 385 +750 430 465 430 465 +1000 485 520 485 515 + +Six Circuits \[See Figure 311.60(D)(3), + +Detail 3.\] +8 46 50 — — +6 60 65 63 68 +4 77 83 81 87 +2 98 105 105 110 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV90105°C +(221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +1 110 120 115 125 +1/0 125 135 130 145 +2/0 145 155 150 160 +3/0 165 175 170 180 +4/0 185 200 190 200 +250 200 220 205 220 +350 240 270 245 275 +500 290 310 290 305 +750 350 375 340 365 +1000 390 420 380 405 + +Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor. + +Table 311.60(C)(80) Ampacities of Three Insulated Aluminum Conductors Cabled Within an Overall + +Covering +(Three-Conductor Cable) in Underground Electrical Ducts (One Cable per Electrical Duct) + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV90105°C +(221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +One Circuit \[See Figure 311.60(D)(3), + +Detail 1.\] +8 46 50 — — +6 61 66 69 74 +4 80 86 89 96 +2 105 110 115 125 +1 120 130 135 145 +1/0 140 150 150 165 +2/0 160 170 170 185 +3/0 180 195 195 210 +4/0 205 220 220 240 +250 230 245 245 265 +350 280 310 295 315 +500 340 365 355 385 +750 425 460 440 475 +1000 495 535 510 545 + +Three Circuits \[See Figure 311.60(D)(3), + +Detail 2.\] +8 41 44 — — + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV90105°C +(221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +6 54 58 59 64 +4 70 75 75 81 +2 90 97 100 105 +1 105 110 110 120 +1/0 120 125 125 135 +2/0 135 145 140 155 +3/0 155 165 160 175 +4/0 175 185 180 195 +250 190 205 200 215 +350 230 250 240 255 +500 280 300 285 305 +750 345 375 350 375 +1000 400 430 400 430 + +Six Circuits \[See Figure 311.60(D)(3), + +Detail 3.\] +8 36 39 — — +6 46 50 49 53 +4 60 65 63 68 +2 77 83 80 86 +1 87 94 90 98 +1/0 99 105 105 110 +2/0 110 120 115 125 +3/0 130 140 130 140 +4/0 145 155 150 160 +250 160 170 160 170 +350 190 205 190 205 +500 230 245 230 245 +750 280 305 275 295 +1000 320 345 315 335 + +Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor. + +Table 311.60(C)(81) Ampacities of Single Insulated Copper Conductors Directly Buried in Earth + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +One Circuit, Three Conductors \[See Figure +311.60(D)(3), Detail 9.\] + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +8 110 115 — — +6 140 150 130 140 +4 180 195 170 180 +2 230 250 210 225 +1 260 280 240 260 +1/0 295 320 275 295 +2/0 335 365 310 335 +3/0 385 415 355 380 +4/0 435 465 405 435 +250 470 510 440 475 +350 570 615 535 575 +500 690 745 650 700 +750 845 910 805 865 +1000 980 1055 930 1005 + +Two Circuits, Six Conductors \[See Figure +311.60(D)(3), Detail 10.\] +8 100 110 — — +6 130 140 120 130 +4 165 180 160 170 +2 215 230 195 210 +1 240 260 225 240 +1/0 275 295 255 275 +2/0 310 335 290 315 +3/0 355 380 330 355 +4/0 400 430 375 405 +250 435 470 410 440 +350 520 560 495 530 +500 630 680 600 645 +750 775 835 740 795 +1000 890 960 855 920 + +Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor. + +Table 311.60(C)(82) Ampacities of Single Insulated Aluminum Conductors Directly Buried in Earth + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +One Circuit, Three Conductors \[See Figure +311.60(D)(3), Detail 9.\] +8 85 90 — — +6 110 115 100 110 +4 140 150 130 140 +2 180 195 165 175 +1 205 220 185 200 +1/0 230 250 215 230 +2/0 265 285 245 260 +3/0 300 320 275 295 +4/0 340 365 315 340 +250 370 395 345 370 +350 445 480 415 450 +500 540 580 510 545 +750 665 720 635 680 +1000 780 840 740 795 + +Two Circuits, Six Conductors \[See Figure +311.60(D)(3), Detail 10.\] +8 80 85 — — +6 100 110 95 100 +4 130 140 125 130 +2 165 180 155 165 +1 190 200 175 190 +1/0 215 230 200 215 +2/0 245 260 225 245 +3/0 275 295 255 275 +4/0 310 335 290 315 +250 340 365 320 345 +350 410 440 385 415 +500 495 530 470 505 +750 610 655 580 625 +1000 710 765 680 730 + +Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor. + +Table 311.60(C)(83) Ampacities of Three Insulated Copper Conductors Cabled Within an Overall Covering +(Three-Conductor Cable), Directly Buried in Earth + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +One Circuit \[See Figure 311.60(D)(3), + +Detail 5.\] +8 85 89 — — +6 105 115 115 120 +4 135 150 145 155 +2 180 190 185 200 +1 200 215 210 225 +1/0 230 245 240 255 +2/0 260 280 270 290 +3/0 295 320 305 330 +4/0 335 360 350 375 +250 365 395 380 410 +350 440 475 460 495 +500 530 570 550 590 +750 650 700 665 720 +1000 730 785 750 810 + +Two Circuits \[See Figure 311.60(D)(3), + +Detail 6.\] +8 80 84 — — +6 100 105 105 115 +4 130 140 135 145 +2 165 180 170 185 +1 185 200 195 210 +1/0 215 230 220 235 +2/0 240 260 250 270 +3/0 275 295 280 305 +4/0 310 335 320 345 +250 340 365 350 375 +350 410 440 420 450 +500 490 525 500 535 +750 595 640 605 650 +1000 665 715 675 730 + +Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor. + +Table 311.60(C)(84) Ampacities of Three Insulated Aluminum Conductors Cabled Within an Overall + +Covering +(Three-Conductor Cable), Directly Buried in Earth + +Conductor Temperature Rating of Conductor + +Size +(AWG or kcmil) +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +One Circuit \[See Figure 311.60(D)(3), + +Detail 5.\] +8 65 70 — — +6 80 88 90 95 +4 105 115 115 125 +2 140 150 145 155 +1 155 170 165 175 +1/0 180 190 185 200 +2/0 205 220 210 225 +3/0 230 250 240 260 +4/0 260 280 270 295 +250 285 310 300 320 +350 345 375 360 390 +500 420 450 435 470 +750 520 560 540 580 +1000 600 650 620 665 + +Two Circuits \[See Figure 311.60(D)(3), + +Detail 6.\] +8 60 66 — — +6 75 83 80 95 +4 100 110 105 115 +2 130 140 135 145 +1 145 155 150 165 +1/0 165 180 170 185 +2/0 190 205 195 210 +3/0 215 230 220 240 +4/0 245 260 250 270 +250 265 285 275 295 +350 320 345 330 355 +500 385 415 395 425 +750 480 515 485 525 +1000 550 590 560 600 + +Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor. + +Table 311.60(C)(85) Ampacities of Three Triplexed Single Insulated Copper Conductors Directly Buried in + +Earth + +Conductor + +Size + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +(AWG or kcmil) 90°C (194°F) Type MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) Type MV-90 +105°C (221°F) Type + +MV-105 +90°C (194°F) Type + +MV-90 +105°C (221°F) Type + +MV-105 + +One Circuit, Three Conductors \[See Figure +311.60(D)(3), Detail 7.\] +8 90 95 — — +6 120 130 115 120 +4 150 165 150 160 +2 195 205 190 205 +1 225 240 215 230 +1/0 255 270 245 260 +2/0 290 310 275 295 +3/0 330 360 315 340 +4/0 375 405 360 385 +250 410 445 390 410 +350 490 580 470 505 +500 590 635 565 605 +750 725 780 685 740 +1000 825 885 770 830 + +Two Circuits, Six Conductors \[See Figure +311.60(D)(3), Detail 8.\] +8 85 90 — — +6 110 115 105 115 +4 140 150 140 150 +2 180 195 175 190 +1 205 220 200 215 +1/0 235 250 225 240 +2/0 265 285 255 275 +3/0 300 320 290 315 +4/0 340 365 325 350 +250 370 395 355 380 +350 445 480 425 455 +500 535 575 510 545 +750 650 700 615 660 +1000 740 795 690 745 + +Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor. + +Table 311.60(C)(86) Ampacities of Three Triplexed Single Insulated Aluminum Conductors Directly + +Buried in Earth + +Conductor + +Size + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +(AWG or kcmil) +90°C (194°F) + +Type MV-90 +105°C (221°F) + +Type MV-105 +90°C (194°F) + +Type MV-90 +105°C (221°F) + +Type MV-105 + +Conductor + +Size +(AWG or kcmil) + +Temperature Rating of Conductor +2001–5000 Volts Ampacity 5001–35,000 Volts Ampacity +90°C (194°F) + +Type MV-90 +105°C (221°F) + +Type MV-105 +90°C (194°F) + +Type MV-90 +105°C (221°F) + +Type MV-105 + +One Circuit, Three Conductors \[See Figure 311.60(D)(3), Detail 7.\] +8 70 75 — — +6 90 100 90 95 +4 120 130 115 125 +2 155 165 145 155 +1 175 190 165 175 +1/0 200 210 190 205 +2/0 225 240 215 230 +3/0 255 275 245 265 +4/0 290 310 280 305 +250 320 350 305 325 +350 385 420 370 400 +500 465 500 445 480 +750 580 625 550 590 +1000 670 725 635 680 + +Two Circuits, Six Conductors \[See Figure 311.60(D)(3), Detail 8.\] +8 65 70 — — +6 85 95 85 90 +4 110 120 105 115 +2 140 150 135 145 +1 160 170 155 170 +1/0 180 195 175 190 +2/0 205 220 200 215 +3/0 235 250 225 245 +4/0 265 285 255 275 +250 290 310 280 300 +350 350 375 335 360 +500 420 455 405 435 +750 520 560 485 525 +1000 600 645 565 605 + +Note: Refer to 311.60(F) for basis of ampacities and Table 311.10(A) for the temperature rating of the conductor. + +#### 311.60(D) Ampacity Adjustment. + +##### 311.60(D)(1) Grounded Shields. + +Ampacities shown in Table 311.60(C)(69), Table 311.60(C)(70), Table 311.60(C)(81), and Table 311.60(C)(82) shall apply for cables with shields grounded at one point only. Where shields for these cables are grounded at more than one point, ampacities shall be adjusted to take into consideration the heating due to shield currents. + +> [!info] Informational Note: +> Tables other than those listed contain the ampacity of cables with shields grounded at multiple points. + +##### 311.60(D)(2) Burial Depth. + +Where the burial depth of direct burial or electrical duct bank circuits is modified from the values shown in a figure or table, ampacities shall be permitted to be modified as indicated in 311.60(D)(2)(a) and (D)(2)(b). No ampacity adjustments shall be required where the burial depth is decreased. + +* (a) Where burial depths are increased in part(s) of an electrical duct run, a decrease in ampacity of the conductors shall not be required, provided the total length of parts of the duct run increased in depth is less than 25 percent of the total run length. + +* (b) Where burial depths are deeper than shown in a specific underground ampacity table or figure, an ampacity derating factor of +6 percent per 300 mm (1 ft) increase in depth for all values of rho shall be permitted. + +##### 311.60(D)(3) Electrical Ducts Entering Equipment Enclosures. + +At locations where electrical ducts enter equipment enclosures from underground, spacing between such ducts, as shown in Figure +311.60(D)(3), shall be permitted to be reduced without requiring the ampacity of conductors therein to be reduced. + +Figure 311.60(D)(3) Cable Installation Dimensions for Use with Table 311.60(C)(77) Through Table +311.60(C)(86). + +##### 311.60(D)(4) Ambient Temperature Correction. + +Ampacities for ambient temperatures other than those specified in the ampacity tables shall be corrected in accordance with Table +311.60(D)(4) or shall be permitted to be calculated using the following equation: + +###### Equation 311.60(D)(4) + +I' = + +I = + +T = + +T ' = + +T = where: ampacity corrected for ambient temperature ampacity shown in the table for T and T temperature rating of conductor (°C) new ambient temperature (°C) ambient temperature used in the table (°C) + +#### 311.60(E) Ampacity in Air. + +Ampacities for conductors and cables in air shall be as specified in Table 311.60(C)(67) through Table 311.60(C)(76). Ampacities shall be based on the following: + +* (1) Conductor temperatures of 90°C (194°F) and 105°C (221°F) + +* (2) Ambient air temperature of 40°C (104°F) + +> [!info] Informational Note: +> See 311.60(D)(4) where the ambient air temperature is other than 40°C (104°F). + +#### 311.60(F) Ampacity in Underground Electrical Ducts and Direct Buried in Earth. + +Table 311.60(D)(4) Ambient Temperature Correction Factors + +For ambient temperatures other than 40°C (104°F), multiply the allowable ampacities specified in the ampacity tables by the appropriate factor shown below. + +Ambient + +Temperature +(°C) + +Temperature Rating of Conductor Ambient + +Temperature +(°F) +90°C 105°C +10 or less 1.26 1.21 50 or less +11–15 1.22 1.18 51–59 +16–20 1.18 1.14 60–68 +21–25 1.14 1.11 69–77 +26–30 1.10 1.07 78–86 +31–35 1.05 1.04 87–95 +36–40 1.00 1.00 96–104 +41–45 0.95 0.96 105–113 +46–50 0.89 0.92 114–122 +51–55 0.84 0.88 123–131 +56–60 0.77 0.83 132–140 +61–65 0.71 0.78 141–149 +66–70 0.63 0.73 150–158 +71–75 0.55 0.68 159–167 +76–80 0.45 0.62 168–176 +81–85 0.32 0.55 177–185 +86–90 — 0.48 186–194 +91–95 — 0.39 195–203 +96–100 — 0.28 204–212 c a c a a + +Ampacities for conductors and cables in underground electrical ducts and direct buried in earth shall be as specified in Table 311.60(C) + +* (77) through Table 311.60(C)(86). Ampacities shall be based on the following: + +* (1) Ambient earth temperature of 20°C (68°F) + +* (2) Arrangement in accordance with Figure 311.60(D)(3) + +* (3) 100 percent load factor + +* (4) Thermal resistance (Rho) of 90 + +* (5) Conductor temperatures 90°C (194°F) and 105°C (221°F) + +* (6) Minimum burial depths to the top electrical ducts or cables shall be in accordance with 300.50. + +* (7) Maximum depth to the top of electrical duct banks shall be 750 mm (30 in.), and maximum depth to the top of direct-buried cables shall be 900 mm (36 in.). + diff --git a/nfpa-70_312_cabinets.md b/nfpa-70_312_cabinets.md new file mode 100644 index 0000000..6296b6d --- /dev/null +++ b/nfpa-70_312_cabinets.md @@ -0,0 +1,341 @@ +--- +id: +aliases: + - nec-312 +tags: + - authorship/other + - destiny/uncertain + - exclude-from-word-count + - status/draft + - topic/construction/electrical + - type/media +title: Article 312 Cabinets, Cutout Boxes, and Meter Socket Enclosures +--- +# Article 312 Cabinets, Cutout Boxes, and Meter Socket Enclosures + +## Part I. Scope and Installation + +### 312.1 Scope. + +This article covers the installation and construction specifications of cabinets, cutout boxes, and meter socket enclosures. It does not apply to equipment operating at over 1000 volts, except as specifically referenced elsewhere in the Code. + +### 312.2 Damp and Wet Locations. + +In damp or wet locations, surface-type enclosures within the scope of this article shall be placed or equipped so as to prevent moisture or water from entering and accumulating within the cabinet or cutout box, and shall be mounted so there is at least 6-mm (1/4-in.) airspace between the enclosure and the wall or other supporting surface. Enclosures installed in wet locations shall be weatherproof. + +For enclosures in wet locations, raceways or cables entering above the level of uninsulated live parts shall use fittings listed for wet locations. + +> [!important] Exception: +> Nonmetallic enclosures shall be permitted to be installed without the airspace on a concrete, masonry, tile, or similar surface. + +> [!info] Informational Note: +> For protection against corrosion, see 300.6. + +### 312.3 Position in Wall. + +In walls of concrete, tile, or other noncombustible material, cabinets shall be installed so that the front edge of the cabinet is not set back of the finished surface more than 6 mm (1/4 in.). In walls constructed of wood or other combustible material, cabinets shall be flush with the finished surface or project therefrom. + +### 312.4 Repairing Noncombustible Surfaces. + +Noncombustible surfaces that are broken or incomplete shall be repaired so there will be no gaps or open spaces greater than 3 mm (1/8 in.) at the edge of the cabinet or cutout box employing a flush-type cover. + +### 312.5 Cabinets, Cutout Boxes, and Meter Socket Enclosures. + +Conductors entering enclosures within the scope of this article shall be protected from abrasion and shall comply with 312.5(A) through (C). + +#### 312.5(A) Openings to Be Closed. + +Openings through which conductors enter shall be closed in an approved manner. + +#### 312.5(B) Metal Cabinets, Cutout Boxes, and Meter Socket Enclosures. + +Where metal enclosures within the scope of this article are installed with messenger-supported wiring, open wiring on insulators, or concealed knob-and-tube wiring, conductors shall enter through insulating bushings or, in dry locations, through flexible tubing extending from the last insulating support and firmly secured to the enclosure. + +#### 312.5(C) Cables. + +Where cable is used, each cable shall be secured to the cabinet, cutout box, or meter socket enclosure. + +> [!important] Exception No. 1: +> Cables with entirely nonmetallic sheaths shall be permitted to enter the top of a surface-mounted enclosure through one or more nonflexible raceways not less than 450 mm (18 in.) and not more than 3.0 m (10 ft) in length, provided all of the following conditions are met: + +* (1) Each cable is fastened within 300 mm (12 in.), measured along the sheath, of the outer end of the raceway. + +* (2) The raceway extends directly above the enclosure and does not penetrate a structural ceiling. + +* (3) A fitting is provided on each end of the raceway to protect the cable(s) from abrasion and the fittings remain accessible after installation. + +* (4) The raceway is sealed or plugged at the outer end using approved means so as to prevent access to the enclosure through the raceway. + +* (5) The cable sheath is continuous through the raceway and extends into the enclosure beyond the fitting not less than 6 mm (1/4 in.). + +* (6) The raceway is fastened at its outer end and at other points in accordance with the applicable article. + +* (7) Where installed as conduit or tubing, the cable fill does not exceed the amount that would be permitted for complete conduit or tubing systems by Table 1 of Chapter 9 of this Code and all applicable notes thereto. Note 2 to the tables in Chapter 9 does not apply to this condition. + +> [!info] Informational Note: +> See Table 1 in Chapter 9, including Note 9, for allowable cable fill in circular raceways. See 310.15(C)(1) for required ampacity reductions for multiple cables installed in a common raceway. + +> [!important] Exception No. 2: +> Single conductors and multiconductor cables shall be permitted to enter enclosures in accordance with 392.46(A) or +(B). + +### 312.6 Deflection of Conductors. + +Conductors at terminals or conductors entering or leaving cabinets, cutout boxes, and meter socket enclosures shall comply with +312.6(A) through (C). + +> [!important] Exception: +> Wire-bending space in enclosures for motor controllers with provisions for one or two wires per terminal shall comply with +430.10(B). + +#### 312.6(A) Width of Wiring Gutters. + +Conductors shall not be deflected within a cabinet or cutout box unless a gutter having a width in accordance with Table 312.6(A) is provided. Conductors in parallel in accordance with 310.10(G) shall be judged on the basis of the number of conductors in parallel. + +Table 312.6(A) Minimum Wire-Bending Space at Terminals and Minimum Width of Wiring Gutters + +Wire Size (AWG or kcmil) Wires per Terminal + +All Other + +Conductors + +Compact Stranded AA-8000 Aluminum + +Alloy Conductors (see Note 2) +1 2 3 4 5 mm in. mm in. mm in. mm in. mm in. +14--10 12--8 Not specified +--- --- --- --- --- --- --- --- +8--6 6--4 38.1 1 1/2 --- --- --- --- --- --- --- --- +4--3 2--1 50.8 2 --- --- --- --- --- --- --- --- +2 1/0 63.5 2 1/2 --- --- --- --- --- --- --- --- +1 2/0 76.2 3 --- --- --- --- --- --- --- --- +1/0--2/0 3/0--4/0 88.9 3 1/2 127 5 178 7 --- --- --- --- +3/0--4/0 250--300 102 4 152 6 203 8 --- --- --- --- +250 350 114 4 1/2 152 6 203 8 254 10 --- --- +300--350 400--500 127 5 203 8 254 10 305 12 --- --- +400--500 600--750 152 6 203 8 254 10 305 12 356 14 +600--700 800--1000 203 8 254 10 305 12 356 14 406 16 +750--900 --- 203 8 305 12 356 14 406 16 457 18 +1000--1250 --- 254 10 --- --- --- --- --- --- --- --- +1500--2000 --- 305 12 --- --- --- --- --- --- --- --- + +Notes: +1. Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector (in the direction that the wire leaves the terminal) to the wall, barrier, or obstruction. +2. This column shall be permitted to be used to determine the minimum wire-bending space for compact stranded aluminum conductors in sizes up to 1000 kcmil and manufactured using AA-8000 series electrical grade aluminum alloy conductor material in accordance with 310.3(B). The minimum width of the wire gutter space shall be determined using the all other conductors value in this table. + +#### 312.6(B) Wire-Bending Space at Terminals. + +Wire-bending space at each terminal shall be provided in accordance with 312.6(B) (1) or (B)(2). + +##### 312.6(B)(1) Conductors Not Entering or Leaving Opposite Wall. + +Table 312.6(A) shall apply where the conductor does not enter or leave the enclosure through the wall opposite its terminal. + +##### 312.6(B)(2) Conductors Entering or Leaving Opposite Wall. + +Table 312.6(B) shall apply where the conductor does enter or leave the enclosure through the wall opposite its terminal. + +> [!important] Exception No. 1: +> Where the distance between the wall and its terminal is in accordance with Table 312.6(A), a conductor shall be permitted to enter or leave an enclosure through the wall opposite its terminal, provided the conductor enters or leaves the enclosure where the gutter joins an adjacent gutter that has a width that conforms to Table 312.6(B) for the conductor. + +> [!important] Exception No. 2: +> A conductor not larger than 350 kcmil shall be permitted to enter or leave an enclosure containing only a meter socket(s) through the wall opposite its terminal, provided the distance between the terminal and the opposite wall is not less than that specified in Table 312.6(A) and the terminal is a lay-in type or removable lug with integral mounting tang, where the terminal is either of the following: + +* (1) Directed toward the opening in the enclosure and within a 45- degree angle of directly facing the enclosure wall + +* (2) Directly facing the enclosure wall and offset not greater than 50 percent of the bending space specified in Table 312.6(A) + +> [!info] Informational Note: +> Offset is the distance measured along the enclosure wall from the axis of the centerline of the terminal to a line passing through the center of the opening in the enclosure. + +Table 312.6(B) Minimum Wire-Bending Space at Terminals + +Wire Size (AWG or kcmil) + +Wires per Terminal +1 2 3 +4 or + +More + +All Other + +Conductors + +Compact Stranded AA-8000 Aluminum Alloy + +Conductors (See Note 3.) mm in. mm in. mm in. mm in. +14--10 12--8 Not specified +--- --- --- --- --- +8 6 38.1 1 1/2 --- --- --- --- --- +6 4 50.8 2 --- --- --- --- --- +4 2 76.2 3 --- --- --- --- --- +3 1 76.2 3 --- --- --- --- --- +2 1/0 88.9 3 1/2 --- --- --- --- --- +1 2/0 114 4 1/2 --- --- --- --- --- +1/0 3/0 140 5 1/2 140 5 1/2 178 7 --- --- +2/0 4/0 152 6 152 6 190 7 1/2 --- --- +3/0 250 165 6 1/2 165 6 1/2 203 8 --- --- +4/0 300 178 7 190 7 1/2 216 8 1/2 --- --- +250 350 216 8 1/2 216 8 1/2 229 9 254 10 +300 400 254 10 254 10 279 11 305 12 +350 500 305 12 305 12 330 13 356 14 +400 600 330 13 330 13 356 14 381 15 +500 700--750 356 14 356 14 381 15 406 16 a a a a b b c c a a d d d d b b e e d d b b e e e e e e d d e e e e e e e e e e e e e e e e + +Wire Size (AWG or kcmil) + +Wires per Terminal +1 2 3 +4 or + +More + +All Other + +Conductors + +Compact Stranded AA-8000 Aluminum Alloy + +Conductors (See Note 3.) mm in. mm in. mm in. mm in. +600 800--900 381 15 406 16 457 18 483 19 +700 1000 406 16 457 18 508 20 559 22 +750 --- 432 17 483 19 559 22 610 24 +800 --- 457 18 508 20 559 22 610 24 +900 --- 483 19 559 22 610 24 610 24 +1000 --- 508 20 --- --- --- --- +1250 --- 559 22 --- --- --- --- +1500 --- 610 24 --- --- --- --- +1750 --- 610 24 --- --- --- --- +2000 --- 610 24 --- --- --- --- + +Notes: +1. Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector in a direction perpendicular to the enclosure wall. +2. For removable and lay-in wire terminals intended for only one wire, bending space shall be permitted to be reduced by the following number of millimeters (inches): +12.7 mm (1/2 in.) +25.4 mm (1 in.) +38.1 mm (1 1/2 in.) +50.8 mm (2 in.) +76.2 mm (3 in.) +3. This column shall be permitted to determine the required wire-bending space for compact stranded aluminum conductors in sizes up to 1000 kcmil and manufactured using AA-8000 series electrical grade aluminum alloy conductor material in accordance with 310.3(B). + +#### 312.6(C) Conductors 4 AWG or Larger. + +Installation shall comply with 300.4(G). + +### 312.7 Space in Enclosures. + +Cabinets and cutout boxes shall have approved space to accommodate all conductors installed in them without crowding. + +### 312.8 Switch and Overcurrent Device Enclosures. + +The wiring space within enclosures for switches and overcurrent devices shall be permitted for other wiring and equipment subject to limitations for specific equipment as provided in 312.8(A) and (B). + +#### 312.8(A) Splices, Taps, and Feed-Through Conductors. + +The wiring space of enclosures for switches or overcurrent devices shall be permitted for conductors feeding through, spliced, or tapping off to other enclosures, switches, or overcurrent devices where all of the following conditions are met: + +* (1) The total of all conductors installed at any cross section of the wiring space does not exceed 40 percent of the cross-sectional area of that space. + +* (2) The total area of all conductors, splices, and taps installed at any cross section of the wiring space does not exceed 75 percent of the cross-sectional area of that space. + +* (3) A warning label complying with 110.21(B) is applied to the enclosure that identifies the closest disconnecting means for any feed-through conductors. e e e e e e e e e e e e e e e e e e e e e e e e a b c d e + +#### 312.8(B) Power Monitoring or Energy Management Equipment. + +The wiring space of enclosures for switches or overcurrent devices shall be permitted to contain power monitoring or energy management equipment in accordance with 312.8(B)(1) through (B)(3). + +##### 312.8(B)(1) Identification. + +The power monitoring or energy management equipment shall be identified as a field installable accessory as part of the listed equipment or is a listed kit evaluated for field installation in switch or overcurrent device enclosures. + +##### 312.8(B)(2) Area. + +The total area of all conductors, splices, taps, and equipment at any cross section of the wiring space shall not exceed 75 percent of the cross-sectional area of that space. + +##### 312.8(B)(3) Conductors. + +Conductors used exclusively for control or instrumentation circuits shall comply with either 312.8(B) (3) (a) or (B)(3)(b). + +* (a) Conductors shall comply with 725.49. + +* (b) Conductors smaller than 18 AWG, but not smaller than 22 AWG for a single conductor and 26 AWG for a multiconductor cable, shall be permitted to be used where the conductors and cable assemblies meet all of the following conditions: + +* (1) Are enclosed within raceways or routed along one or more walls of the enclosure and secured at intervals that do not exceed 250 mm (10 in.) + +* (2) Are secured within 250 mm (10 in.) of terminations + +* (3) Are secured to prevent contact with current carrying components within the enclosure + +* (4) Are rated for the system voltage and not less than 600 volts + +* (5) Have a minimum insulation temperature rating of 90°C + +### 312.9 Side or Back Wiring Spaces or Gutters. + +Cabinets and cutout boxes shall be provided with back-wiring spaces, gutters, or wiring compartments as required by 312.11(C) and +(D). + +## Part II. Construction Specifications + +### 312.10 Material. + +Cabinets, cutout boxes, and meter socket enclosures shall comply with 312.10(A) through (C). + +#### 312.10(A) Metal Cabinets and Cutout Boxes. + +Metal enclosures within the scope of this article shall be protected both inside and outside against corrosion. + +#### 312.10(B) Strength. + +The design and construction of enclosures within the scope of this article shall be such as to secure ample strength and rigidity. If constructed of sheet steel, the metal thickness shall not be less than 1.35 mm (0.053 in.) uncoated. + +#### 312.10(C) Nonmetallic Cabinets. + +Nonmetallic cabinets shall be listed, or they shall be submitted for approval prior to installation. + +### 312.11 Spacing. + +The spacing within cabinets and cutout boxes shall comply with 312.11(A) through (D). + +#### 312.11(A) General. + +Spacing within cabinets and cutout boxes shall provide approved spacing for the distribution of wires and cables placed in them and for a separation between metal parts of devices and apparatus mounted within them in accordance with 312.11(A)(1), (A)(2), and (A)(3). + +##### 312.11(A)(1) Base. + +Other than at points of support, there shall be an airspace of at least 1.59 mm (0.0625 in.) between the base of the device and the wall of any metal cabinet or cutout box in which the device is mounted. + +##### 312.11(A)(2) Doors. + +There shall be an airspace of at least 25.4 mm (1.00 in.) between any live metal part, including live metal parts of enclosed fuses, and the door. + +> [!important] Exception: +> Where the door is lined with an approved insulating material or is of a thickness of metal not less than 2.36 mm (0.093 in.) uncoated, the airspace shall not be less than 12.7 mm (0.500 in.). + +##### 312.11(A)(3) Live Parts. + +There shall be an airspace of at least 12.7 mm (0.500 in.) between the walls, back, gutter partition, if of metal, or door of any cabinet or cutout box and the nearest exposed current-carrying part of devices mounted within the cabinet where the voltage does not exceed +250. This spacing shall be increased to at least 25.4 mm (1.00 in.) for voltages of 251 to 1000, nominal. + +> [!important] Exception: +> Where the conditions in 312.11(A)(2), Exception, are met, the airspace for nominal voltages from 251 to 600 shall be permitted to be not less than 12.7 mm (0.500 in.). + +#### 312.11(B) Switch Clearance. + +Cabinets and cutout boxes shall be deep enough to allow the closing of the doors when 30-ampere branch-circuit panelboard switches are in any position, when combination cutout switches are in any position, or when other single-throw switches are opened as far as their construction permits. + +#### 312.11(C) Wiring Space. + +Cabinets and cutout boxes that contain devices or apparatus connected within the cabinet or box to more than eight conductors, including those of branch circuits, meter loops, feeder circuits, power circuits, and similar circuits, but not including the supply circuit or a continuation thereof, shall have back-wiring spaces or one or more side-wiring spaces, side gutters, or wiring compartments. + +#### 312.11(D) Wiring Space --- Enclosure. + +Side-wiring spaces, side gutters, or side-wiring compartments of cabinets and cutout boxes shall be made tight enclosures by means of covers, barriers, or partitions extending from the bases of the devices contained in the cabinet, to the door, frame, or sides of the cabinet. + +> [!important] Exception: +> Side-wiring spaces, side gutters, and side-wiring compartments of cabinets shall not be required to be made tight enclosures where those side spaces contain only conductors that enter the cabinet directly opposite to the devices where they terminate. + +Partially enclosed back-wiring spaces shall be provided with covers to complete the enclosure. Wiring spaces that are required by +312.11(C) and are exposed when doors are open shall be provided with covers to complete the enclosure. Where space is provided for feed-through conductors and for splices as required in 312.8, additional barriers shall not be required. \ No newline at end of file diff --git a/nfpa-70_314_boxes.md b/nfpa-70_314_boxes.md index c3c102e..d744f8f 100644 --- a/nfpa-70_314_boxes.md +++ b/nfpa-70_314_boxes.md @@ -15,20 +15,438 @@ title: Article 314 Outlet, Device, Pull, and Junction Boxes; Conduit Bodies; Fit ## Part I. Scope and General - +### 314.1 Scope. + +This article covers the installation and use of all boxes and conduit bodies used as outlet, device, junction, or pull boxes, depending on their use, and handhole enclosures. Cast metal, sheet metal, nonmetallic, and other boxes such as FS, FD, and larger boxes are not classified as conduit bodies. This article also includes installation requirements for fittings used to join raceways and to connect raceways and cables to boxes and conduit bodies. + +### 314.2 Round Boxes. + +Round boxes shall not be used where conduits or connectors requiring the use of locknuts or bushings are to be connected to the side of the box. + +### 314.3 Nonmetallic Boxes. + +Nonmetallic boxes shall be permitted only with open wiring on insulators, concealed knob-and-tube wiring, cabled wiring methods with entirely nonmetallic sheaths, flexible cords, and nonmetallic raceways. + +> [!important] Exception No. 1: +> Where internal bonding means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables. + +> [!important] Exception No. 2: +> Where integral bonding means with a provision for attaching an equipment bonding jumper inside the box are provided between all threaded entries in nonmetallic boxes listed for the purpose, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables. + +### 314.4 Metal Boxes. + +Metal boxes shall be grounded and bonded in accordance with Parts I, IV, V, VI, VII, and X of Article 250 as applicable, except as permitted in 250.112(I). ## Part II. Installation - +### 314.15 Damp or Wet Locations. + +In damp or wet locations, boxes, conduit bodies, outlet box hoods, and fittings shall be placed or equipped so as to prevent moisture from entering or accumulating within the box, conduit body, or fitting. Boxes, conduit bodies, outlet box hoods, and fittings installed in wet locations shall be listed for use in wet locations. Approved drainage openings not smaller than 3 mm (1⁄8 in.) and not larger than +6 mm (1⁄4 in.) in diameter shall be permitted to be installed in the field in boxes or conduit bodies listed for use in damp or wet locations. + +For installation of listed drain fittings, larger openings are permitted to be installed in the field in accordance with manufacturer’s instructions. + +> [!info] Informational Note No. 1: +> For boxes in floors, see 314.27(B). + +> [!info] Informational Note No. 2: +> For protection against corrosion, see 300.6. + +### 314.16 Number of Conductors in Outlet, Device, and Junction Boxes, and Conduit Bodies. + +Boxes and conduit bodies shall be of an approved size to provide free space for all enclosed conductors. In no case shall the volume of the box, as calculated in 314.16(A), be less than the fill calculation as calculated in 314.16(B). The minimum volume for conduit bodies shall be as calculated in 314.16(C). + +The provisions of this section shall not apply to terminal housings supplied with motors or generators. + +> [!info] Informational Note: +> For volume requirements of motor or generator terminal housings, see 430.12. + +Boxes and conduit bodies enclosing conductors 4 AWG or larger shall also comply with the provisions of 314.28. Outlet and device boxes shall also comply with 314.24. + +#### 314.16(A) Box Volume Calculations. + +The volume of a wiring enclosure (box) shall be the total volume of the assembled sections and, where used, the space provided by plaster rings, domed covers, extension rings, and so forth, that are marked with their volume or are made from boxes the dimensions of which are listed in Table 314.16(A). Where a box is provided with one or more securely installed barriers, the volume shall be apportioned to each of the resulting spaces. Each barrier, if not marked with its volume, shall be considered to take up 8.2 cm3 (1⁄2 in.3) if metal, and 16.4 cm (1.0 in.3) if nonmetallic. + +##### 314.16(A)(1) Standard Boxes. + +The volumes of standard boxes that are not marked with their volume shall be as given in Table 314.16(A). + +##### 314.16(A)(2) Other Boxes. + +Boxes 1650 cm3 (100 in.3) or less, other than those described in Table 314.16(A), and nonmetallic boxes shall be durably and legibly marked by the manufacturer with their volume(s). Boxes described in Table 314.16(A) that have a volume larger than is designated in the table shall be permitted to have their volume marked as required by this section. + +###### Table 314.16(A) Metal Boxes + +Box Trade Size Minimum Volume + +Maximum Number of Conductors* +(arranged by AWG size) mm in. cm in. 18 16 14 12 10 8 6 +100 × 32 (4 × 1 1⁄4) round/octagonal 205 12.5 8 7 6 5 5 5 2 +100 × 38 (4 × 1 1⁄2) round/octagonal 254 15.5 10 8 7 6 6 5 3 +100 × 54 (4 × 2 1⁄8) round/octagonal 353 21.5 14 12 10 9 8 7 4 +100 × 32 (4× 1 1⁄4) square 295 18.0 12 10 9 8 7 6 3 +100 × 38 (4 × 1 1⁄2) square 344 21.0 14 12 10 9 8 7 4 +100 × 54 (4 × 2 1⁄8) square 497 30.3 20 17 15 13 12 10 6 +120 × 32 (411⁄16 × 1 1⁄4) square 418 25.5 17 14 12 11 10 8 5 +120 × 38 (411⁄16 × 1 1⁄2) square 484 29.5 19 16 14 13 11 9 5 +120 × 54 (411⁄16 × 2 1⁄8) square 689 42.0 28 24 21 18 16 14 8 +75 × 50 × 38 (3 × 2 × 1 1⁄2) device 123 7.5 5 4 3 3 3 2 1 +75 × 50 × 50 (3 × 2 × 2) device 164 10.0 6 5 5 4 4 3 2 +3 3 +3 3 +3 3 +3 3 + +Box Trade Size Minimum Volume + +Maximum Number of Conductors* +(arranged by AWG size) mm in. cm in. 18 16 14 12 10 8 6 +75× 50 × 57 (3× 2 × 2 1⁄4) device 172 10.5 7 6 5 4 4 3 2 +75 × 50 × 65 (3 × 2 × 2 1⁄2) device 205 12.5 8 7 6 5 5 4 2 +75 × 50 × 70 (3 × 2 × 2 3⁄4) device 230 14.0 9 8 7 6 5 4 2 +75 × 50 × 90 (3 × 2 × 3 1⁄2) device 295 18.0 12 10 9 8 7 6 3 +100 × 54 × 38 (4 × 2 1⁄8 × 1 1⁄2) device 169 10.3 6 5 5 4 4 3 2 +100 × 54 × 48 (4 × 2 1⁄8 × 1 7⁄8) device 213 13.0 8 7 6 5 5 4 2 +100 × 54 × 54 (4 × 2 1⁄8 × 2 1⁄8) device 238 14.5 9 8 7 6 5 4 2 +95 × 50 × 65 (3 3⁄4 × 2 × 2 1⁄2) masonry box/gang 230 14.0 9 8 7 6 5 4 2 +95 × 50 × 90 (3 3⁄4 × 2 × 3 1⁄2) masonry box/gang 344 21.0 14 12 10 9 8 7 4 min. 44.5 depth FS — single cover/gang (1 3⁄4) 221 13.5 9 7 6 6 5 4 2 min. 60.3 depth FD — single cover/gang (2 3⁄8) 295 18.0 12 10 9 8 7 6 3 min. 44.5 depth FS — multiple cover/gang (1 3⁄4) 295 18.0 12 10 9 8 7 6 3 min. 60.3 depth FD — multiple cover/gang (2 3⁄8) 395 24.0 16 13 12 10 9 8 4 +*Where no volume allowances are required by 314.16(B)(2) through (B)(5). + +#### 314.16(B) Box Fill Calculations. + +The volumes in paragraphs 314.16(B)(1) through (B)(5), as applicable, shall be added together. No allowance shall be required for small fittings such as locknuts and bushings. Each space within a box installed with a barrier shall be calculated separately. + +##### 314.16(B)(1) Conductor Fill. + +Each conductor that originates outside the box and terminates or is spliced within the box shall be counted once, and each conductor that passes through the box without splice or termination shall be counted once. Each loop or coil of unbroken conductor not less than twice the minimum length required for free conductors in 300.14 shall be counted twice. The conductor fill shall be calculated using + +Table 314.16(B). A conductor, no part of which leaves the box, shall not be counted. + +> [!important] Exception: +> An equipment grounding conductor or conductors or not over four fixture wires smaller than 14 AWG, or both, shall be permitted to be omitted from the calculations where they enter a box from a domed luminaire or similar canopy and terminate within that box. + +##### 314.16(B)(2) Clamp Fill. + +Where one or more internal cable clamps, whether factory or field supplied, are present in the box, a single volume allowance in accordance with Table 314.16(B) shall be made based on the largest conductor present in the box. No allowance shall be required for a cable connector with its clamping mechanism outside the box. + +A clamp assembly that incorporates a cable termination for the cable conductors shall be listed and marked for use with specific nonmetallic boxes. Conductors that originate within the clamp assembly shall be included in conductor fill calculations covered in +314.16(B)(1) as though they entered from outside the box. The clamp assembly shall not require a fill allowance, but the volume of the portion of the assembly that remains within the box after installation shall be excluded from the box volume as marked in 314.16(A)(2). + +##### 314.16(B)(3) Support Fittings Fill. + +Where one or more luminaire studs or hickeys are present in the box, a single volume allowance in accordance with Table 314.16(B) shall be made for each type of fitting based on the largest conductor present in the box. + +##### 314.16(B)(4) Device or Equipment Fill. + +For each yoke or strap containing one or more devices or equipment, a double volume allowance in accordance with Table 314.16(B) shall be made for each yoke or strap based on the largest conductor connected to a device(s) or equipment supported by that yoke or strap. A device or utilization equipment wider than a single 50 mm (2 in.) device box as described in Table 314.16(A) shall have double volume allowances provided for each gang required for mounting. +3 3 + +Table 314.16(B) Volume Allowance Required per Conductor + +Size of Conductor (AWG) + +Free Space Within Box for Each Conductor cm in. +18 24.6 1.50 +16 28.7 1.75 +14 32.8 2.00 +12 36.9 2.25 +10 41.0 2.50 +8 49.2 3.00 +6 81.9 5.00 + +##### 314.16(B)(5) Equipment Grounding Conductor Fill. + +Where up to four equipment grounding conductors or equipment bonding jumpers enter a box, a single volume allowance in accordance with Table 314.16(B) shall be made based on the largest equipment grounding conductor or equipment bonding jumper entering the box. A 1⁄4 volume allowance shall be made for each additional equipment grounding conductor or equipment bonding jumper that enters the box, based on the largest equipment grounding conductor or equipment bonding conductor. + +#### 314.16(C) Conduit Bodies. + +##### 314.16(C)(1) General. + +Conduit bodies enclosing 6 AWG conductors or smaller, other than short-radius conduit bodies as described in 314.16(C)(3), shall have a cross-sectional area not less than twice the cross-sectional area of the largest conduit or tubing to which they can be attached. The maximum number of conductors permitted shall be the maximum number permitted by Table 1 of Chapter 9 for the conduit or tubing to which it is attached. + +##### 314.16(C)(2) With Splices, Taps, or Devices. + +Only those conduit bodies that are durably and legibly marked by the manufacturer with their volume shall be permitted to contain splices, taps, or devices. The maximum number of conductors shall be calculated in accordance with 314.16(B). Conduit bodies shall be supported in a rigid and secure manner. + +##### 314.16(C)(3) Short Radius Conduit Bodies. + +Conduit bodies such as capped elbows and service-entrance elbows that enclose conductors 6 AWG or smaller, and are only intended to enable the installation of the raceway and the contained conductors, shall not contain splices, taps, or devices and shall be of an approved size to provide free space for all conductors enclosed in the conduit body. + +### 314.17 Conductors Entering Boxes, Conduit Bodies, or Fittings. + +Conductors entering boxes, conduit bodies, or fittings shall be protected from abrasion and shall comply with 314.17(A) through (D). + +#### 314.17(A) Openings to Be Closed. + +Openings through which conductors enter shall be closed in a manner identified for the application. + +#### 314.17(B) Boxes and Conduit Bodies. + +The installation of the conductors in boxes and conduit bodies shall comply with 314.17(B)(1) through (B)(4). + +##### 314.17(B)(1) Conductors Entering Through Individual Holes or Through Flexible Tubing. + +For messenger-supported wiring, open wiring on insulators, or concealed knob-and-tube wiring, the conductors shall enter the box through individual holes. In installations where metal boxes or conduit bodies are used with conductors unprotected by flexible tubing, the individual openings shall be provided with insulating bushings. Where flexible tubing is used to enclose the conductors, the tubing shall extend from the last insulating support to not less than 6 mm (1⁄4 in.) inside the box or conduit body and beyond any cable clamp. + +The wiring method shall be secured to the box or conduit body. + +##### 314.17(B)(2) Conductors Entering Through Cable Clamps. + +Where cable assemblies with nonmetallic sheathes are used, the sheath shall extend not less than 6 mm (1⁄4 in.) inside the box and beyond any cable clamp. Except as provided in 300.15(C), the wiring method shall be secured to the box or conduit body. +3 3 + +> [!important] Exception: +> Where nonmetallic-sheathed cable is used with single gang nonmetallic boxes not larger than a nominal size 57 mm × +100 mm (2 1⁄4 in. × 4 in.) mounted in walls or ceilings, and where the cable is fastened within 200 mm (8 in.) of the box measured along the sheath and where the sheath extends through a cable knockout not less than 6 mm (1⁄4 in.), securing the cable to the box shall not be required. Multiple cable entries shall be permitted in a single cable knockout opening. + +##### 314.17(B)(3) Conductors Entering Through Raceways. + +Where the raceway is complete between boxes, conduit bodies, or both and encloses individual conductors or nonmetallic cable assemblies or both, the conductors or cable assemblies shall not be required to be additionally secured. Where raceways enclose cable assemblies as provided in 300.15(C), the cable assembly shall not be required to be additionally secured within the box or conduit body. + +##### 314.17(B)(4) Temperature Limitation. + +Nonmetallic boxes and conduit bodies shall be suitable for the lowest temperature-rated conductor entering the box or conduit body. + +#### 314.17(C) Conductors 4 AWG or Larger. + +Installation shall comply with 300.4(G). + +> [!info] Informational Note: +> See 110.12(A) for requirements on closing unused cable and raceway knockout openings. + +### 314.19 Boxes Enclosing Flush Devices or Flush Equipment. + +Boxes used to enclose flush devices or flush equipment shall be of such design that the devices or equipment will be completely enclosed on the back and sides, and substantial support for the devices or equipment will be provided. Screws for supporting the box shall not also be used to attach a device or equipment. + +### 314.20 Flush-Mounted Installations. + +Installations within or behind a surface of concrete, tile, gypsum, plaster, or other noncombustible material, including boxes employing a flush-type cover or faceplate, shall be made so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back of the finished surface more than 6 mm (1⁄4 in.). + +Installations within a surface of wood or other combustible surface material, boxes, plaster rings, extension rings, or listed extenders shall extend to the finished surface or project therefrom. + +### 314.21 Repairing Noncombustible Surfaces. + +Noncombustible surfaces that are broken or incomplete around boxes employing a flush-type cover or faceplate shall be repaired so there will be no gaps or open spaces greater than 3 mm (1⁄8 in.) at the edge of the box. + +### 314.22 Surface Extensions. + +Surface extensions shall be made by mounting and mechanically securing an extension ring over the box. Equipment grounding shall be in accordance with Part VI of Article 250. + +> [!important] Exception: +> A surface extension shall be permitted to be made from the cover of a box where the cover is designed so it is unlikely to fall off or be removed if its securing means becomes loose. The wiring method shall be flexible for an approved length that permits removal of the cover and provides access to the box interior and shall be arranged so that any grounding continuity is independent of the connection between the box and cover. + +### 314.23 Supports. + +Enclosures within the scope of this article shall be supported in accordance with one or more of the provisions in 314.23(A) through (H). + +#### 314.23(A) Surface Mounting. + +An enclosure mounted on a building or other surface shall be rigidly and securely fastened in place. If the surface does not provide rigid and secure support, additional support in accordance with other provisions of this section shall be provided. + +#### 314.23(B) Structural Mounting. + +An enclosure supported from a structural member or from grade shall be rigidly supported either directly or by using a metal, polymeric, or wood brace. + +##### 314.23(B)(1) Nails and Screws. + +Nails and screws, where used as a fastening means, shall secure boxes by using brackets on the outside of the enclosure, or by using mounting holes in the back or in one or more sides of the enclosure, or they shall pass through the interior within 6 mm (1⁄4 in.) of the back or ends of the enclosure. Screws shall not be permitted to pass through the box unless exposed threads in the box are protected using approved means to avoid abrasion of conductor insulation. Mounting holes made in the field shall be approved. + +##### 314.23(B)(2) Braces. + +Metal braces shall be protected against corrosion and formed from metal that is not less than 0.51 mm (0.020 in.) thick uncoated. Wood braces shall have a cross section not less than nominal 25 mm × 50 mm (1 in. × 2 in.). Wood braces in wet locations shall be treated for the conditions. Polymeric braces shall be identified as being suitable for the use. + +#### 314.23(C) Mounting in Finished Surfaces. + +An enclosure mounted in a finished surface shall be rigidly secured thereto by clamps, anchors, or fittings identified for the application. + +#### 314.23(D) Suspended Ceilings. + +An enclosure mounted to structural or supporting elements of a suspended ceiling shall be not more than 1650 cm (100 in. ) in size and shall be securely fastened in place in accordance with either 314.23(D)(1) or (D)(2). + +##### 314.23(D)(1) Framing Members. + +An enclosure shall be fastened to the framing members by mechanical means such as bolts, screws, or rivets, or by the use of clips or other securing means identified for use with the type of ceiling framing member(s) and enclosure(s) employed. The framing members shall be supported in an approved manner and securely fastened to each other and to the building structure. + +##### 314.23(D)(2) Support Wires. + +The installation shall comply with 300.11(A). The enclosure shall be secured, using identified methods, to ceiling support wire(s), including any additional support wire(s) installed for ceiling support. Support wire(s) used for enclosure support shall be fastened at each end so as to be taut within the ceiling cavity. + +#### 314.23(E) Raceway-Supported Enclosure, Without Devices, Luminaires, or Lampholders. + +An enclosure that does not contain a device(s), other than splicing devices, or supports a luminaire(s), a lampholder, or other equipment and is supported by entering raceways shall not exceed 1650 cm (100 in. ) in size. It shall have threaded entries or identified hubs. It shall be supported by two or more conduits threaded wrenchtight into the enclosure or hubs. Each conduit shall be secured within 900 mm (3 ft) of the enclosure, or within 450 mm (18 in.) of the enclosure if all conduit entries are on the same side. + +> [!important] Exception: +> The following wiring methods shall be permitted to support a conduit body of any size, including a conduit body constructed with only one conduit entry, provided that the trade size of the conduit body is not larger than the largest trade size of the conduit or tubing: + +* (1) Intermediate metal conduit, Type IMC +* (2) Rigid metal conduit, Type RMC +* (3) Rigid polyvinyl chloride conduit, Type PVC +* (4) Reinforced thermosetting resin conduit, Type RTRC +* (5) Electrical metallic tubing, Type EMT + +#### 314.23(F) Raceway-Supported Enclosures, with Devices, Luminaires, or Lampholders. + +An enclosure that contains a device(s), other than splicing devices, +or supports a luminaire(s), a lampholder, or other equipment +and is supported by entering raceways +shall not exceed 1650 cm3(100 in.3) in size. +It shall have threaded entries or identified hubs. +It shall be supported by two or more conduits threaded wrenchtight into the enclosure or hubs. +Each conduit shall be secured within 450 mm (18 in.) of the enclosure. + +> [!important] Exception No. 1: +> Rigid metal or intermediate metal conduit shall be permitted to support a conduit body of any size, including a conduit body constructed with only one conduit entry, provided the trade size of the conduit body is not larger than the largest trade size of the conduit. + +> [!important] Exception No. 2: +> An unbroken length(s) of rigid or intermediate metal conduit shall be permitted to support a box used for luminaire or lampholder support, or to support a wiring enclosure that is an integral part of a luminaire and used in lieu of a box in accordance with 300.15(B), where all of the following conditions are met: + +* (1) The conduit is securely fastened at a point so that the length of conduit beyond the last point of conduit support does not exceed 900 mm (3 ft). + +* (2) The unbroken conduit length before the last point of conduit support is 300 mm (12 in.) or greater, and that portion of the conduit is securely fastened at some point not less than 300 mm (12 in.) from its last point of support. + +* (3) Where accessible to unqualified persons, the luminaire or lampholder, measured to its lowest point, is at least 2.5 m (8 ft) above grade or standing area and at least 900 mm (3 ft) measured horizontally to the 2.5 m (8 ft) elevation from windows, doors, porches, fire escapes, or similar locations. + +* (4) A luminaire supported by a single conduit does not exceed 300 mm (12 in.) in any direction from the point of conduit entry. + +* (5) The weight supported by any single conduit does not exceed 9 kg (20 lb). + +* (6) At the luminaire or lampholder end, the conduit(s) is threaded wrenchtight into the box, conduit body, integral wiring enclosure, or identified hubs. Where a box or conduit body is used for support, the luminaire shall be secured directly to the box or conduit body, or through a threaded conduit nipple not over 75 mm (3 in.) long. + +#### 314.23(G) Enclosures in Concrete or Masonry. + +An enclosure supported by embedment shall be identified as suitably protected from corrosion and securely embedded in concrete or masonry. + +#### 314.23(H) Pendant Boxes. + +An enclosure supported by a pendant shall comply with 314.23(H)(1) or (H)(2). + +##### 314.23(H)(1) Flexible Cord. + +A box shall be supported from a multiconductor cord or cable in an approved manner that protects the conductors against strain, such as a strain-relief connector threaded into a box with a hub. + +##### 314.23(H)(2) Conduit. + +A box supporting lampholders or luminaires, or wiring enclosures within luminaires used in lieu of boxes in accordance with 300.15(B), shall be supported by rigid or intermediate metal conduit stems. For stems longer than 450 mm (18 in.), the stems shall be connected to the wiring system with listed swivel hangers suitable for the location. At the luminaire end, the conduit(s) shall be threaded wrenchtight into the box, wiring enclosure, or identified hubs. + +Where supported by only a single conduit, the threaded joints shall be prevented from loosening by the use of set-screws or other effective means, or the luminaire, at any point, shall be at least 2.5 m (8 ft) above grade or standing area and at least 900 mm (3 ft) measured horizontally to the 2.5 m (8 ft) elevation from windows, doors, porches, fire escapes, or similar locations. A luminaire supported by a single conduit shall not exceed 300 mm (12 in.) in any horizontal direction from the point of conduit entry. + +### 314.24 Depth of Boxes. + +Outlet and device boxes shall have an approved depth to allow equipment installed within them to be mounted properly and without likelihood of damage to conductors within the box. + +#### 314.24(A) Outlet Boxes Without Enclosed Devices or Utilization Equipment. + +Outlet boxes that do not enclose devices or utilization equipment shall have a minimum internal depth of 12.7 mm (1⁄2 in.). + +#### 314.24(B) Outlet and Device Boxes with Enclosed Devices or Utilization Equipment. + +Outlet and device boxes that enclose devices or utilization equipment shall have a minimum internal depth that accommodates the rearward projection of the equipment and the size of the conductors that supply the equipment. The internal depth shall include, where used, that of any extension boxes, plaster rings, or raised covers. The internal depth shall comply with all applicable provisions of +314.24(B)(1) through (B)(5). + +##### 314.24(B)(1) Large Equipment. + +Boxes that enclose devices or utilization equipment that projects more than 48 mm (1 7⁄8 in.) rearward from the mounting plane of the box shall have a depth that is not less than the depth of the equipment plus 6 mm (1⁄4 in.). + +##### 314.24(B)(2) Conductors Larger Than 4 AWG. + +Boxes that enclose devices or utilization equipment supplied by conductors larger than 4 AWG shall be identified for their specific function. + +Exception to (2): Devices or utilization equipment supplied by conductors larger than 4 AWG shall be permitted to be mounted on or in junction and pull boxes larger than 1650 cm (100 in. ) if the spacing at the terminals meets the requirements of 312.6. + +##### 314.24(B)(3) Conductors 8, 6, or 4 AWG. + +Boxes that enclose devices or utilization equipment supplied by 8, 6, or 4 AWG conductors shall have an internal depth that is not less than 52.4 mm (21⁄16 in.). + +##### 314.24(B)(4) Conductors 12 or 10 AWG. + +Boxes that enclose devices or utilization equipment supplied by 12 or 10 AWG conductors shall have an internal depth that is not less than 30.2 mm (13⁄16 in.). Where the equipment projects rearward from the mounting plane of the box by more than 25 mm (1 in.), the box shall have a depth not less than that of the equipment plus 6 mm (1⁄4 in.). + +##### 314.24(B)(5) Conductors 14 AWG and Smaller. + +Boxes that enclose devices or utilization equipment supplied by 14 AWG or smaller conductors shall have a depth that is not less than +23.8 mm (15⁄16 in.). +3 3 + +Exception to (1) through (5): Devices or utilization equipment that is listed to be installed with specified boxes shall be permitted. + +### 314.25 Covers and Canopies. + +In completed installations, each box shall have a cover, faceplate, lampholder, or luminaire canopy, except where the installation complies with 410.24(B). Screws used for the purpose of attaching covers, or other equipment, to the box shall be either machine screws matching the thread gauge and size that is integral to the box or shall be in accordance with the manufacturer’s instructions. + +#### 314.25(A) Nonmetallic or Metal Covers and Plates. + +Nonmetallic or metal covers and plates shall be permitted. Where metal covers or plates are used, they shall comply with the grounding requirements of 250.110. + +> [!info] Informational Note: +> For additional grounding requirements, see 410.42 for metal luminaire canopies, and 404.12 and 406.6(B) for metal faceplates. + +#### 314.25(B) Exposed Combustible Wall or Ceiling Finish. + +Where a luminaire canopy or pan is used, any combustible wall or ceiling finish exposed between the edge of the canopy or pan and the outlet box shall be covered with noncombustible material if required by 410.23. + +#### 314.25(C) Flexible Cord Pendants. + +Covers of outlet boxes and conduit bodies having holes through which flexible cord pendants pass shall be provided with identified bushings or shall have smooth, well-rounded surfaces on which the cords may bear. So-called hard rubber or composition bushings shall not be used. + +### 314.27 Outlet Boxes. + +#### 314.27(A) Boxes at Luminaire or Lampholder Outlets. + +Outlet boxes or fittings designed for the support of luminaires and lampholders, and installed as required by 314.23, shall be permitted to support a luminaire or lampholder. + +##### 314.27(A)(1) Vertical Surface Outlets. + +Boxes used at luminaire or lampholder outlets in or on a vertical surface shall be identified and marked on the interior of the box to indicate the maximum weight of the luminaire that is permitted to be supported by the box if other than 23 kg (50 lb). + +> [!important] Exception: +> A vertically mounted luminaire or lampholder weighing not more than 3 kg (6 lb) shall be permitted to be supported on other boxes or plaster rings that are secured to other boxes, provided that the luminaire or its supporting yoke, or the lampholder, is secured to the box with no fewer than two No. 6 or larger screws. + +##### 314.27(A)(2) Ceiling Outlets. + +At every outlet used exclusively for lighting, the box shall be designed or installed so that a luminaire or lampholder may be attached. + +Boxes shall be required to support a luminaire weighing a minimum of 23 kg (50 lb). A luminaire that weighs more than 23 kg (50 lb) shall be supported independently of the outlet box, unless the outlet box is listed for not less than the weight to be supported. The interior of the box shall be marked by the manufacturer to indicate the maximum weight the box shall be permitted to support. + +#### 314.27(B) Floor Boxes. + +Boxes listed specifically for this application shall be used for receptacles located in the floor. + +> [!important] Exception: +> Where the authority having jurisdiction judges them free from likely exposure to physical damage, moisture, and dirt, boxes located in elevated floors of show windows and similar locations shall be permitted to be other than those listed for floor applications. + +Receptacles and covers shall be listed as an assembly for this type of location. + +#### 314.27(C) Boxes at Ceiling-Suspended (Paddle) Fan Outlets. + +Outlet boxes or outlet box systems used as the sole support of a ceiling-suspended (paddle) fan shall be listed, shall be marked by their manufacturer as suitable for this purpose, and shall not support ceiling-suspended (paddle) fans that weigh more than 32 kg (70 lb). For outlet boxes or outlet box systems designed to support ceiling-suspended (paddle) fans that weigh more than 16 kg (35 lb), the required marking shall include the maximum weight to be supported. + +Outlet boxes mounted in the ceilings of habitable rooms of dwelling occupancies in a location acceptable for the installation of a ceilingsuspended +(paddle) fan shall comply with one of the following: + +* (1) Listed for the sole support of ceiling-suspended (paddle) fans + +* (2) An outlet box complying with the applicable requirements of 314.27 and providing access to structural framing capable of supporting of a ceiling-suspended (paddle) fan bracket or equivalent + +#### 314.27(D) Utilization Equipment. + +Boxes used for the support of utilization equipment other than ceiling-suspended (paddle) fans shall meet the requirements of +314.27(A) for the support of a luminaire that is the same size and weight. + +> [!important] Exception: +> Utilization equipment weighing not more than 3 kg (6 lb) shall be permitted to be supported on other boxes or plaster rings that are secured to other boxes, provided the equipment or its supporting yoke is secured to the box with no fewer than two No. 6 or larger screws. + +#### 314.27(E) Separable Attachment Fittings. + +Outlet boxes required in 314.27 shall be permitted to support listed locking support and mounting receptacles used in combination with compatible attachment fittings. The combination shall be identified for the support of equipment within the weight and mounting orientation limits of the listing. Where the supporting receptacle is installed within a box, it shall be included in the fill calculation covered in 314.16(B)(4). + ### 314.28 Pull and Junction Boxes and Conduit Bodies. Boxes and conduit bodies used as pull or junction boxes shall comply with 314.28(A) through (E). -> [!exception] -> Terminal housings supplied with motors shall comply with -> the provisions of 430.12. +> [!important] Exception: +> > Terminal housings supplied with motors shall comply with the provisions of 430.12. #### (A) Minimum Size. @@ -60,7 +478,7 @@ in the same row on the same wall of the box. Each row shall be calculated individually, and the single row that provides the maximum distance shall be used. -> [!exception] +> [!important] Exception: > Where a raceway or cable entry is in the wall of a box or conduit body > opposite a removable cover, > the distance from that wall to the cover @@ -104,7 +522,7 @@ of the conductors specified in the marking, based on the type of conductor identified as part of the product listing. -> [!info] +> [!info] Informational Note: > Unless otherwise specified, > the applicable product standards evaluate the fill markings covered here > based on conductors with Type XHHW insulation. @@ -133,7 +551,7 @@ in pull and junction boxes over 1650 cm3 (100 in.3) for connections of conductors where installed in boxes and where the installation complies with 314.28(E)(1) through (5). -> [!exception] +> [!important] Exception: > Equipment grounding terminal bars shall be permitted in smaller enclosures. ##### (1) Installation. @@ -170,4 +588,141 @@ so the power distribution block terminals are unobstructed following installatio ### 314.40 Metal Boxes, Conduit Bodies, and Fittings. - +#### 314.40(A) Corrosion Resistant. + +Metal boxes, conduit bodies, and fittings shall be corrosion resistant or shall be well-galvanized, enameled, or otherwise properly coated inside and out to prevent corrosion. + +> [!info] Informational Note: +> See 300.6 for limitation in the use of boxes and fittings protected from corrosion solely by enamel. + +#### 314.40(B) Thickness of Metal. + +Sheet steel boxes not over 1650 cm3(100 in.3) in size shall be made from steel not less than 1.59 mm (0.0625 in.) thick. The wall of a malleable iron box or conduit body and a die-cast or permanent-mold cast aluminum, brass, bronze, or zinc box or conduit body shall not be less than 2.38 mm (3⁄32 in.) thick. Other cast metal boxes or conduit bodies shall have a wall thickness not less than 3.17 mm (1⁄8 in.). + +> [!important] Exception No. 1: +> Listed boxes and conduit bodies shown to have equivalent strength and characteristics shall be permitted to be made of thinner or other metals. + +> [!important] Exception No. 2: +> The walls of listed short radius conduit bodies, as covered in 314.16(C)(2), shall be permitted to be made of thinner metal. + +#### 314.40(C) Metal Boxes Over 1650 cm3 (100 in.3). + +Metal boxes over 1650 cm3 (100 in.3) in size shall be constructed so as to be of ample strength and rigidity. If of sheet steel, the metal thickness shall not be less than 1.35 mm (0.053 in.) uncoated. + +#### 314.40(D) Equipment Grounding Conductor Provisions. + +A means shall be provided in each metal box for the connection of an equipment grounding conductor. The means shall be permitted to be a tapped hole or equivalent. + +### 314.41 Covers. + +Metal covers shall be of the same material as the box or conduit body with which they are used, or they shall be lined with firmly attached insulating material that is not less than 0.79 mm (1⁄32 in.) thick, or they shall be listed for the purpose. Metal covers shall be the same thickness as the boxes or conduit body for which they are used, or they shall be listed for the purpose. Covers of porcelain or other approved insulating materials shall be permitted if of such form and thickness as to afford the required protection and strength. + +### 314.42 Bushings. + +Covers of outlet boxes and conduit bodies having holes through which flexible cord pendants may pass shall be provided with approved bushings or shall have smooth, well-rounded surfaces on which the cord may bear. Where individual conductors pass through a metal cover, a separate hole equipped with a bushing of suitable insulating material shall be provided for each conductor. Such separate holes shall be connected by a slot as required by 300.20. + +### 314.43 Nonmetallic Boxes. + +Provisions for supports or other mounting means for nonmetallic boxes shall be outside of the box, or the box shall be constructed so as to prevent contact between the conductors in the box and the supporting screws. + +### 314.44 Marking. + +All boxes and conduit bodies, covers, extension rings, plaster rings, and the like shall be durably and legibly marked with the manufacturer’s name or trademark. + +## Part IV. Pull and Junction Boxes, Conduit Bodies, and Handhole Enclosures for Use on Systems over + +1000 Volts, Nominal + +### 314.70 General. + +#### 314.70(A) Pull and Junction Boxes. + +Where pull and junction boxes are used on systems over 1000 volts, the installation shall comply with the provisions of Part IV and with the following general provisions of this article: + +* (1) Part I, 314.2; 314.3; and 314.4 + +* (2) Part II, 314.15; 314.17; 314.20; 314.23(A), (B), or (G); 314.28(B); and 314.29 + +* (3) Part III, 314.40(A) and (C); and 314.41 + +#### 314.70(B) Conduit Bodies. + +Where conduit bodies are used on systems over 1000 volts, the installation shall comply with the provisions of Part IV and with the following general provisions of this article: + +* (1) Part I, 314.4 + +* (2) Part II, 314.15; 314.17; 314.23(A), (E), or (G); 314.28(A) (3); and 314.29 + +* (3) Part III, 314.40(A) and 314.41 + +#### 314.70(C) Handhole Enclosures. + +Where handhole enclosures are used on systems over 1000 volts, the installation shall comply with the provisions of Part IV and with the following general provisions of this article: + +* (1) Part I, 314.3 and 314.4 + +* (2) Part II, 314.15; 314.17; 314.23(G); 314.28(B); 314.29; and 314.30 + +### 314.71 Size of Pull and Junction Boxes, Conduit Bodies, and Handhole Enclosures. + +Pull and junction boxes and handhole enclosures shall provide approved space and dimensions for the installation of conductors, and they shall comply with the specific requirements of this section. Conduit bodies shall be permitted if they meet the dimensional requirements for boxes. + +#### 314.71(A) For Straight Pulls. + +The length of the box shall not be less than 48 times the outside diameter, over sheath, of the largest shielded or lead-covered conductor or cable entering the box. The length shall not be less than 32 times the outside diameter of the largest nonshielded conductor or cable. + +#### 314.71(B) For Angle or U Pulls. + +##### 314.71(B)(1) Distance to Opposite Wall. + +The distance between each cable or conductor entry inside the box and the opposite wall of the box shall not be less than 36 times the outside diameter, over sheath, of the largest cable or conductor. This distance shall be increased for additional entries by the amount of the sum of the outside diameters, over sheath, of all other cables or conductor entries through the same wall of the box. + +> [!important] Exception No. 1: +> Where a conductor or cable entry is in the wall of a box opposite a removable cover, the distance from that wall to the cover shall be permitted to be not less than the bending radius for the conductors as provided in 300.34. + +> [!important] Exception No. 2: +> Where cables are nonshielded and not lead covered, the distance of 36 times the outside diameter shall be permitted to be reduced to 24 times the outside diameter. + +##### 314.71(B)(2) Distance Between Entry and Exit. + +The distance between a cable or conductor entry and its exit from the box shall not be less than 36 times the outside diameter, over sheath, of that cable or conductor. + +> [!important] Exception: +> Where cables are nonshielded and not lead covered, the distance of 36 times the outside diameter shall be permitted to be reduced to 24 times the outside diameter. + +#### 314.71(C) Removable Sides. + +One or more sides of any pull box shall be removable. + +### 314.72 Construction and Installation Requirements. + +#### 314.72(A) Corrosion Protection. + +Boxes shall be made of material inherently resistant to corrosion or shall be suitably protected, both internally and externally, by enameling, galvanizing, plating, or other means. + +#### 314.72(B) Passing Through Partitions. + +Suitable bushings, shields, or fittings having smooth, rounded edges shall be provided where conductors or cables pass through partitions and at other locations where necessary. + +#### 314.72(C) Complete Enclosure. + +Boxes shall provide a complete enclosure for the contained conductors or cables. + +#### 314.72(D) Wiring Is Accessible. + +Boxes and conduit bodies shall be installed so that the conductors are accessible without removing any fixed part of the building or structure. Working space shall be provided in accordance with 110.34. + +#### 314.72(E) Suitable Covers. + +Boxes shall be closed by suitable covers securely fastened in place. +Underground box covers that weigh over 45 kg (100 lb) +shall be considered meeting this requirement. +Covers for boxes shall be permanently marked +“DANGER — HIGH VOLTAGE — KEEP OUT.” + +The marking shall be on the outside of the box cover and shall be readily visible. +Letters shall be block type and at least 13 mm (1⁄2 in.) in height. + +#### 314.72(F) Suitable for Expected Handling. + +Boxes and their covers shall be capable of withstanding the handling to which they are likely to be subjected. diff --git a/nfpa-70_320_armored-cable.md b/nfpa-70_320_armored-cable.md index b2aa274..7636a57 100644 --- a/nfpa-70_320_armored-cable.md +++ b/nfpa-70_320_armored-cable.md @@ -6,7 +6,7 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: "Article 320 Armored Cable: Type AC" diff --git a/nfpa-70_330_mc-cable.md b/nfpa-70_330_mc-cable.md new file mode 100644 index 0000000..a829dd7 --- /dev/null +++ b/nfpa-70_330_mc-cable.md @@ -0,0 +1,222 @@ +--- +id: +aliases: + - nec-330 +tags: + - authorship/other + - destiny/uncertain + - exclude-from-word-count + - status/draft + - topic/construction/electrical + - type/media +title: "Article 330 Metal-Clad Cable: Type MC" +--- +# Article 330 Metal-Clad Cable: Type MC + +## Part I. General + +### 330.1 Scope. + +This article covers the use, installation, and construction specifications of metal-clad cable, Type MC. + +### 330.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +#### Metal Clad Cable, Type MC. + +A factory assembly of one or more insulated circuit conductors with or without optical fiber members enclosed in an armor of interlocking metal tape, or a smooth or corrugated metallic sheath. + +### 330.6 Listing Requirements. + +Type MC cable shall be listed. Fittings used for connecting Type MC cable to boxes, cabinets, or other equipment shall be listed and identified for such use. + +## Part II. Installation + +### 330.10 Uses Permitted. + +#### 330.10(A) General Uses. + +Type MC cable shall be permitted as follows: + +* (1) For services, feeders, and branch circuits. + +* (2) For power, lighting, control, and signal circuits. + +* (3) Indoors or outdoors. + +* (4) Exposed or concealed. + +* (5) To be direct buried where identified for such use. + +* (6) In cable tray where identified for such use. + +* (7) In any raceway. + +* (8) As aerial cable on a messenger. + +* (9) In hazardous (classified) locations where specifically permitted by other articles in this Code. + +* (10) In dry locations and embedded in plaster finish on brick or other masonry except in damp or wet locations. + +* (11) In wet locations where a corrosion-resistant jacket is provided over the metallic covering and any of the following conditions are met: + * a. The metallic covering is impervious to moisture. + * b. A jacket resistant to moisture is provided under the metal covering. + * c. The insulated conductors under the metallic covering are listed for use in wet locations. + +* (12) Where single-conductor cables are used, all phase conductors and, where used, the grounded conductor shall be grouped together to minimize induced voltage on the sheath. + +#### 330.10(B) Specific Uses. + +Type MC cable shall be permitted to be installed in compliance with Parts II and III of Article 725 and 770.133 as applicable and in accordance with 330.10(B)(1) through (B)(4). + +> [!info] Informational Note: +> The "Uses Permitted" is not an all-inclusive list. + +##### 330.10(B)(1) Cable Tray. + +Type MC cable installed in cable tray shall comply with 392.10, 392.12, 392.18, 392.20, 392.22, 392.30, 392.46, 392.56, 392.60(C), and 392.80. + +##### 330.10(B)(2) Direct Buried. + +Direct-buried cable shall comply with 300.5 or 300.50, as appropriate. + +##### 330.10(B)(3) Installed as Service-Entrance Cable. + +Type MC cable installed as service-entrance cable shall be permitted in accordance with 230.43. + +##### 330.10(B)(4) Installed Outside of Buildings or Structures or as Aerial Cable. + +Type MC cable installed outside of buildings or structures or as aerial cable shall comply with 225.10, 396.10, and 396.12. + +### 330.12 Uses Not Permitted. + +Type MC cable shall not be used under either of the following conditions: + +* (1) Where subject to physical damage + +* (2) Where exposed to any of the destructive corrosive conditions in (a) or (b), unless the metallic sheath or armor is resistant to the conditions or is protected by material resistant to the conditions: + * a. Direct buried in the earth or embedded in concrete unless identified for direct burial + * b. Exposed to cinder fills, strong chlorides, caustic alkalis, or vapors of chlorine or of hydrochloric acids + +### 330.15 Exposed Work. + +Exposed runs of cable, except as provided in 300.11(B), shall closely follow the surface of the building finish or of running boards. + +Exposed runs shall also be permitted to be installed on the underside of joists where supported at each joist and located so as not to be subject to physical damage. + +### 330.17 Through or Parallel to Framing Members. + +Type MC cable shall be protected in accordance with 300.4(A), (C), and (D) where installed through or parallel to framing members. + +### 330.23 In Accessible Attics. + +The installation of Type MC cable in accessible attics or roof spaces shall also comply with 320.23. + +### 330.24 Bending Radius. + +Bends in Type MC cable shall be so made that the cable will not be damaged. The radius of the curve of the inner edge of any bend shall not be less than required in 330.24(A) through (C). + +#### 330.24(A) Smooth Sheath. + +* (1) Ten times the external diameter of the metallic sheath for cable not more than 19 mm (3⁄4 in.) in external diameter + +* (2) Twelve times the external diameter of the metallic sheath for cable more than 19 mm (3⁄4 in.) but not more than 38 mm (1 1/2 in.) in external diameter + +* (3) Fifteen times the external diameter of the metallic sheath for cable more than 38 mm (1 1⁄2 in.) in external diameter + +#### 330.24(B) Interlocked-Type Armor or Corrugated Sheath. + +Seven times the external diameter of the metallic sheath. + +#### 330.24(C) Shielded Conductors. + +Twelve times the overall diameter of one of the individual conductors or seven times the overall diameter of the multiconductor cable, whichever is greater. + +### 330.30 Securing and Supporting. + +#### 330.30(A) General. + +Type MC cable shall be supported and secured by staples; cable ties listed and identified for securement and support; straps, hangers, or similar fittings; or other approved means designed and installed so as not to damage the cable. + +#### 330.30(B) Securing. + +Unless otherwise provided, cables shall be secured at intervals not exceeding 1.8 m (6 ft). Cables containing four or fewer conductors sized no larger than 10 AWG shall be secured within 300 mm (12 in.) of every box, cabinet, fitting, or other cable termination. In vertical installations, listed cables with ungrounded conductors 250 kcmil and larger shall be permitted to be secured at intervals not exceeding 3 m (10 ft). + +#### 330.30(C) Supporting. + +Unless otherwise provided, cables shall be supported at intervals not exceeding 1.8 m (6 ft). + +Horizontal runs of Type MC cable installed in wooden or metal framing members or similar supporting means shall be considered supported and secured where such support does not exceed 1.8-m (6-ft) intervals. + +#### 330.30(D) Unsupported Cables. + +Type MC cable shall be permitted to be unsupported and unsecured where the cable complies with any of the following: + +* (1) Is fished between access points through concealed spaces in finished buildings or structures and supporting is impractical. + +* (2) Is not more than 1.8 m (6 ft) in length from the last point of cable support to the point of connection to luminaires or other electrical equipment and the cable and point of connection are within an accessible ceiling. + +* (3) Is Type MC of the interlocked armor type in lengths not exceeding 900 mm (3 ft) from the last point where it is securely fastened and is used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation. + +For the purpose of this section, Type MC cable fittings shall be permitted as a means of cable support. + +### 330.31 Single Conductors. + +Where single-conductor cables with a nonferrous armor or sheath are used, the installation shall comply with 300.20. + +### 330.80 Ampacity. + +The ampacity of Type MC cable shall be determined in accordance with 310.14 or 311.60 for 14 AWG and larger conductors and in accordance with Table 402.5 for 18 AWG and 16 AWG conductors. The installation shall not exceed the temperature ratings of terminations and equipment. + +#### 330.80(A) Type MC Cable Installed in Cable Tray. + +The ampacities for Type MC cable installed in cable tray shall be determined in accordance with 392.80. + +#### 330.80(B) Single Type MC Conductors Grouped Together. + +Where single Type MC conductors are grouped together in a triangular or square configuration and installed on a messenger or exposed with a maintained free airspace of not less than 2.15 times one conductor diameter (2.15 × O.D.) of the largest conductor contained within the configuration and adjacent conductor configurations or cables, the ampacity of the conductors shall not exceed the allowable ampacities in the following tables: + +* (1) Table 310.20 for conductors rated 0 volts through 2000 volts + +* (2) Table 311.60(C)(67) and Table 311.60(C)(68) for conductors rated over 2000 volts + +#### 330.80(C) Thermal Insulation. + +Where more than two Type MC cables containing two or more current-carrying conductors in each cable are installed in contact with thermal insulation, caulk, or sealing foam without maintaining spacing between cables, the ampacity of each conductor shall be adjusted in accordance with Table 310.15(C)(1). + +## Part III. Construction Specifications + +### 330.104 Conductors. + +For ungrounded, grounded, and equipment grounding conductors, the minimum conductor sizes shall be 14 AWG copper, nickel, or nickel-coated copper and 12 AWG aluminum or copper-clad aluminum. + +For control and signal conductors minimum conductor sizes shall be 18 AWG copper, nickel, or nickel-coated copper, 14 AWG copperclad aluminum, and 12 AWG aluminum. + +### 330.108 Equipment Grounding Conductor. + +Where Type MC cable is used to provide an equipment grounding conductor, it shall comply with 250.118(10) and 250.122. + +### 330.112 Insulation. + +Insulated conductors shall comply with 330.112(A) or (B). + +#### 330.112(A) 1000 Volts or Less. + +Insulated conductors in sizes 18 AWG and 16 AWG shall be of a type listed in Table 402.3, with a maximum operating temperature not less than 90°C (194°F) and as permitted by 725.49. Conductors larger than 16 AWG shall be of a type listed in Table 310.4(A) or of a type identified for use in Type MC cable. + +#### 330.112(B) Over 1000 Volts. + +Insulated conductors shall be of a type listed in Table 310.4(B) and Table 311.10(A). + +### 330.116 Sheath. + +Metallic covering shall be one of the following types: smooth metallic sheath, corrugated metallic sheath, or interlocking metal tape armor. The metallic sheath shall be continuous and close fitting. A nonmagnetic sheath or armor shall be used on single conductor Type MC. +Supplemental protection of an outer covering of corrosion-resistant material shall be permitted and shall be required where such protection is needed. The sheath shall not be used as a current-carrying conductor. + +> [!info] Informational Note: +> See 300.6 for protection against corrosion. + +### 330.130 Hazardous (Classified) Locations. + +Where required to be marked MC-HL, the cable shall be listed and shall have a gas/vapor tight continuous corrugated metallic sheath, an overall jacket of suitable polymeric material, and a separate equipment grounding conductor. diff --git a/nfpa-70_332_mi-cable.md b/nfpa-70_332_mi-cable.md new file mode 100644 index 0000000..a05e04d --- /dev/null +++ b/nfpa-70_332_mi-cable.md @@ -0,0 +1,161 @@ +--- +id: +aliases: + - nec-332 +tags: + - authorship/other + - destiny/uncertain + - exclude-from-word-count + - status/draft + - topic/construction/electrical + - type/media +title: "Article 332 Mineral-Insulated, Metal-Sheathed Cable: Type MI" +--- +# Article 332 Mineral-Insulated, Metal-Sheathed Cable: Type MI + +## Part I. General + +### 332.1 Scope. + +This article covers the use, installation, and construction specifications +for mineral-insulated, metal-sheathed cable, Type MI. + +### 332.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +#### Mineral-Insulated, Metal-Sheathed Cable, Type MI. + +A factory assembly of one or more conductors +insulated with a highly compressed refractory mineral insulation +and enclosed in a liquidtight and gastight continuous copper or alloy steel sheath. + +### 332.6 Listing Requirements. + +Type MI cable and associated fittings shall be listed. + +## Part II. Installation + +### 332.10 Uses Permitted. + +Type MI cable shall be permitted as follows: + +* (1) For services, feeders, and branch circuits + +* (2) For power, lighting, control, and signal circuits + +* (3) In dry, wet, or continuously moist locations + +* (4) Indoors or outdoors + +* (5) Where exposed or concealed + +* (6) Where embedded in plaster, concrete, fill, or other masonry, whether above or below grade + +* (7) In hazardous (classified) locations where specifically permitted by other articles in this Code + +* (8) Where exposed to oil and gasoline + +* (9) Where exposed to corrosive conditions not deteriorating to its sheath + +* (10) In underground runs where suitably protected against physical damage and corrosive conditions + +* (11) In or attached to cable tray + +> [!info] Informational Note: +> The "Uses Permitted" is not an all-inclusive list. + +### 332.12 Uses Not Permitted. + +Type MI cable shall not be used under the following conditions or in the following locations: + +* (1) In underground runs unless protected from physical damage, where necessary + +* (2) Where exposed to conditions that are destructive and corrosive to the metallic sheath, unless additional protection is provided + +### 332.17 Through or Parallel to Framing Members. + +Type MI cable shall be protected in accordance with 300.4 where installed through or parallel to framing members. + +### 332.24 Bending Radius. + +Bends in Type MI cable shall be so made that the cable will not be damaged. The radius of the inner edge of any bend shall not be less than required as follows: + +* (1) Five times the external diameter of the metallic sheath for cable not more than 19 mm (3⁄4 in.) in external diameter + +* (2) Ten times the external diameter of the metallic sheath for cable greater than 19 mm (3⁄4 in.) but not more than 25 mm (1 in.) in external diameter + +### 332.30 Securing and Supporting. + +Type MI cable shall be supported and secured by staples, straps, hangers, or similar fittings, designed and installed so as not to damage the cable, at intervals not exceeding 1.8 m (6 ft). + +#### 332.30(A) Horizontal Runs Through Holes and Notches. + +In other than vertical runs, cables installed in accordance with 300.4 shall be considered supported and secured where such support does not exceed 1.8 m (6 ft) intervals. + +#### 332.30(B) Unsupported Cable. + +Type MI cable shall be permitted to be unsupported where the cable is fished between access points through concealed spaces in finished buildings or structures and supporting is impracticable. + +#### 332.30(C) Cable Trays. + +All MI cable installed in cable trays shall comply with 392.30(A). + +### 332.31 Single Conductors. + +Where single-conductor cables are used, +all phase conductors and, where used, the neutral conductor +shall be grouped together to minimize induced voltage on the sheath. + +### 332.40 Boxes and Fittings. + +#### 332.40(A) Fittings. + +Fittings used for connecting Type MI cable to boxes, +cabinets, or other equipment +shall be identified for such use. + +#### 332.40(B) Terminal Seals. + +Where Type MI cable terminates, +an end seal fitting shall be installed immediately after stripping +to prevent the entrance of moisture into the insulation. +The conductors extending beyond the sheath +shall be individually provided with an insulating material. + +### 332.80 Ampacity. + +The ampacity of Type MI cable shall be determined in accordance with 310.14. +The conductor temperature at the end seal fitting shall not exceed the temperature rating of the listed end seal fitting, and the installation shall not exceed the temperature ratings of terminations or equipment. + +#### 332.80(A) Type MI Cable Installed in Cable Tray. + +The ampacities for Type MI cable installed in cable tray shall be determined in accordance with 392.80(A). + +#### 332.80(B) Single Type MI Conductors Grouped Together. + +Where single Type MI conductors are grouped together in a triangular or square configuration, +as required by 332.31, +and installed on a messenger or exposed with a maintained free air space +of not less than 2.15 times one conductor diameter (2.15 × O.D.) +of the largest conductor contained within the configuration +and adjacent conductor configurations or cables, +the ampacity of the conductors shall not exceed the allowable ampacities of Table 310.17. + +## Part III. Construction Specifications + +### 332.104 Conductors. + +Type MI cable conductors shall be of solid copper, nickel, or nickel-coated copper with a resistance corresponding to standard AWG and kcmil sizes. + +### 332.108 Equipment Grounding Conductor. + +Where the outer sheath is made of copper, it shall provide an adequate path to serve as an equipment grounding conductor. Where the outer sheath is made of steel, a separate equipment grounding conductor shall be provided. + +### 332.112 Insulation. + +The conductor insulation in Type MI cable shall be a highly compressed refractory mineral that provides proper spacing for all conductors. + +### 332.116 Sheath. + +The outer sheath shall be of a continuous construction to provide mechanical protection and moisture seal. diff --git a/nfpa-70_334_nm-cable.md b/nfpa-70_334_nm-cable.md index 3180922..8ba169d 100644 --- a/nfpa-70_334_nm-cable.md +++ b/nfpa-70_334_nm-cable.md @@ -23,15 +23,15 @@ This article covers the use, installation, and construction specifications of no The definitions in this section shall apply within this article and throughout the Code. -### Nonmetallic-Sheathed Cable. +#### Nonmetallic-Sheathed Cable. A factory assembly of two or more insulated conductors enclosed within an overall nonmetallic jacket. -### Type NM. +#### Type NM. Insulated conductors enclosed within an overall nonmetallic jacket. -### Type NMC. +#### Type NMC. Insulated conductors enclosed within an overall, corrosion resistant, nonmetallic jacket. diff --git a/nfpa-70_422_appliances.md b/nfpa-70_422_appliances.md new file mode 100644 index 0000000..69991d8 --- /dev/null +++ b/nfpa-70_422_appliances.md @@ -0,0 +1,14 @@ +--- +id: +aliases: + - nec-422 +tags: + - authorship/other + - destiny/permanent/entry-point + - exclude-from-word-count + - status/incomplete + - topic/construction/electrical + - type/media +title: Article 422 Appliances +--- +# Article 422 Appliances diff --git a/nfpa-70_424.md b/nfpa-70_424.md new file mode 100644 index 0000000..4926444 --- /dev/null +++ b/nfpa-70_424.md @@ -0,0 +1,14 @@ +--- +id: +aliases: + - nec-424 +tags: + - authorship/other + - destiny/permanent/entry-point + - exclude-from-word-count + - status/incomplete + - topic/construction/electrical + - type/media +title: Article 424 Fixed Electric Space-Heating Equipment +--- +# Article 424 Fixed Electric Space-Heating Equipment diff --git a/nfpa-70_430_motors.md b/nfpa-70_430_motors.md index d59f930..6cb21d6 100644 --- a/nfpa-70_430_motors.md +++ b/nfpa-70_430_motors.md @@ -6,7 +6,7 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: Article 430 Motors, Motor Circuits, and Controllers @@ -294,7 +294,7 @@ Enclosures for motor controllers and disconnecting means shall not be used as ju Minimum wire-bending space within the enclosures for motor controllers shall be in accordance with Table 430.10(B) where measured in a straight line from the end of the lug or wire connector (in the direction the wire leaves the terminal) to the wall or barrier. Where alternate wire termination means are substituted for that supplied by the manufacturer of the controller, they shall be of a type identified by the manufacturer for use with the controller and shall not reduce the minimum wire-bending space. -Table 430.10(B) Minimum Wire-Bending Space at the Terminals of Enclosed Motor Controllers +##### Table 430.10(B) Minimum Wire-Bending Space at the Terminals of Enclosed Motor Controllers Size of Wire (AWG or kcmil) Wires per Terminal 1 2 @@ -387,7 +387,7 @@ Where these terminal housings enclose rigidly mounted motor terminals, the termi | 250 or less | 6 mm (1⁄4 in.) | 6 mm (1⁄4 in.) | | Over 250 – 1000 | 10 mm (3⁄8 in.) | 10 mm (3⁄8 in.) | -Table 430.12(C)(2) Usable Volumes — Fixed Terminals +#### Table 430.12(C)(2) Usable Volumes — Fixed Terminals | Power-Supply Conductor Size (AWG) | Minimum Usable Volume per Power-Supply Conductor | | --------------------------------- | ------------------------------------------------ | @@ -510,7 +510,7 @@ For a part-winding connected motor, the ampacity of the branch-circuit conductor Conductors for a motor used in a short-time, intermittent, periodic, or varying duty application shall have an ampacity of not less than the percentage of the motor nameplate current rating shown in Table 430.22(E), unless the authority having jurisdiction grants special permission for conductors of lower ampacity. -Table 430.22(E) Duty-Cycle Service +##### Table 430.22(E) Duty-Cycle Service Classification of Service @@ -597,7 +597,7 @@ For other than continuous duty, these conductors shall have an ampacity, in perc Where the secondary resistor is separate from the controller, the ampacity of the conductors between controller and resistor shall not be less than that shown in Table 430.23(C). -Table 430.23(C) Secondary Conductor +##### Table 430.23(C) Secondary Conductor | Resistor Duty Classification | Ampacity of Conductor in Percent of Full-Load Secondary Current | |:---------------------------- | ---------------------------------------------------------------:| @@ -864,7 +864,7 @@ Where fuses are used for motor overload protection, a fuse shall be inserted in Where devices other than fuses are used for motor overload protection, Table 430.37 shall govern the minimum allowable number and location of overload units such as trip coils or relays. -Table 430.37 Overload Units +#### Table 430.37 Overload Units Kind of @@ -966,7 +966,7 @@ The motor branch-circuit short-circuit and ground-fault protective device shall A protective device that has a rating or setting not exceeding the value calculated according to the values given in Table 430.52 shall be used. -Table 430.52 Maximum Rating or Setting of Motor Branch-Circuit Short-Circuit and Ground-Fault +##### Table 430.52 Maximum Rating or Setting of Motor Branch-Circuit Short-Circuit and Ground-Fault Protective Devices @@ -1254,15 +1254,13 @@ The overcurrent protection for conductors shall be provided as specified in 430. ##### 430.72(B)(1) Separate Overcurrent Protection. Where the motor branch-circuit short-circuit and ground-fault protective device does not provide protection in accordance with -430.72(B)(2), separate overcurrent protection shall be provided. The overcurrent protection shall not exceed the values specified in - -Column A of Table 430.72(B). +430.72(B)(2), separate overcurrent protection shall be provided. The overcurrent protection shall not exceed the values specified in Column A of Table 430.72(B). ##### 430.72(B)(2) Branch-Circuit Overcurrent Protective Device. Conductors shall be permitted to be protected by the motor branch-circuit short-circuit and ground-fault protective device and shall require only short-circuit and ground-fault protection. Where the conductors do not extend beyond the motor control equipment enclosure, the rating of the protective device(s) shall not exceed the value specified in Column B of Table 430.72(B). Where the conductors extend beyond the motor control equipment enclosure, the rating of the protective device(s) shall not exceed the value specified in Column C of Table 430.72(B). -Table 430.72(B) Maximum Rating of Overcurrent Protective Device in Amperes +##### Table 430.72(B) Maximum Rating of Overcurrent Protective Device in Amperes Column A @@ -1513,7 +1511,7 @@ One pole of the controller shall be permitted to be placed in a permanently grou Each motor shall be provided with an individual controller. -> [!important] Exception No. 1: +> [!important] Exception No. 1: ^87-ex1 > For motors rated 1000 volts or less, a single controller rated at not less than the equivalent horsepower, as determined in accordance with 430.110(C)(1), of all the motors in the group shall be permitted to serve the group under any of the following conditions: * (1) Where a number of motors drive several parts of a single machine or piece of apparatus, such as metal and woodworking machines, cranes, hoists, and similar apparatus @@ -1522,7 +1520,7 @@ Each motor shall be provided with an individual controller. * (3) Where a group of motors is located in a single room within sight from the controller location -> [!important] Exception No. 2: +> [!important] Exception No. 2: ^87-ex1 > A branch-circuit disconnecting means serving as the controller as allowed in 430.81(A) shall be permitted to serve more than one motor. ### 430.88 Adjustable-Speed Motors. @@ -1606,11 +1604,7 @@ The minimum wire-bending space at the motor control center terminals and minimum Spacings between motor control center bus terminals and other bare metal parts shall not be less than specified in Table 430.97(D). -#### 430.97(E) Barriers. - -Barriers shall be placed in all service-entrance motor control centers to isolate service busbars and terminals from the remainder of the motor control center. - -Table 430.97(D) Minimum Spacing Between Bare Metal Parts +##### Table 430.97(D) Minimum Spacing Between Bare Metal Parts Nominal @@ -1635,6 +1629,10 @@ Not over 250 volts, nominal Not over 600 volts, nominal 50.8 2 25.4 1 25.4 1 +#### 430.97(E) Barriers. + +Barriers shall be placed in all service-entrance motor control centers to isolate service busbars and terminals from the remainder of the motor control center. + ### 430.98 Marking. #### 430.98(A) Motor Control Centers. @@ -1817,8 +1815,7 @@ Where two or more motors are used together or where one or more motors are used The rating of the disconnecting means shall be determined from the sum of all currents, including resistance loads, at the full-load condition and also at the locked-rotor condition. The combined full-load current and the combined locked-rotor current so obtained shall be considered as a single motor for the purpose of this requirement as follows. -The full-load current equivalent to the horsepower rating of each motor shall be selected from Table 430.247, Table 430.248, Table -430.249, or Table 430.250. These full-load currents shall be added to the rating in amperes of other loads to obtain an equivalent fullload current for the combined load. +The full-load current equivalent to the horsepower rating of each motor shall be selected from Table 430.247, Table 430.248, Table 430.249, or Table 430.250. These full-load currents shall be added to the rating in amperes of other loads to obtain an equivalent full-load current for the combined load. The locked-rotor current equivalent to the horsepower rating of each motor shall be selected from Table 430.251(A) or Table 430.251(B). The locked-rotor currents shall be added to the rating in amperes of other loads to obtain an equivalent locked-rotor current for the combined load. Where two or more motors or other loads cannot be started simultaneously, the largest sum of locked-rotor currents of a motor or group of motors that can be started simultaneously and the full-load currents of other concurrent loads shall be permitted to be used to determine the equivalent locked-rotor current for the simultaneous combined loads. In cases where different current ratings are obtained when applying these tables, the largest value obtained shall be used. @@ -1865,15 +1862,11 @@ An oil switch used on a circuit whose rating does not exceed 1000 volts or 100 a Each motor shall be provided with an individual disconnecting means. -> [!important] Exception: -> A single disconnecting means shall be permitted to serve a group of motors under any one of the conditions of (1), (2), and -(3). The single disconnecting means shall be rated in accordance with 430.110(C). - -* (1) Where a number of motors drive several parts of a single machine or piece of apparatus, such as metal- and woodworking machines, cranes, and hoists. - -* (2) Where a group of motors is under the protection of one set of branch-circuit protective devices as permitted by 430.53(A). - -* (3) Where a group of motors is in a single room within sight from the location of the disconnecting means. +> [!important] Exception: ^112-ex +> A single disconnecting means shall be permitted to serve a group of motors under any one of the conditions of (1), (2), and (3). The single disconnecting means shall be rated in accordance with 430.110(C). +> * (1) Where a number of motors drive several parts of a single machine or piece of apparatus, such as metal- and woodworking machines, cranes, and hoists. +> * (2) Where a group of motors is under the protection of one set of branch-circuit protective devices as permitted by 430.53(A). +> * (3) Where a group of motors is in a single room within sight from the location of the disconnecting means. ### 430.113 Energy from More Than One Source. @@ -1957,10 +1950,10 @@ Adjustable-speed drive systems shall protect against motor overtemperature condi * (2) Adjustable-speed drive system with load and speed-sensitive overload protection and thermal memory retention upon shutdown or power loss -Exception to (2): Thermal memory retention upon shutdown or power loss is not required for continuous duty loads. +> [!important] Exception to (2): +> Thermal memory retention upon shutdown or power loss is not required for continuous duty loads. -* (3) Overtemperature protection relay utilizing thermal sensors embedded in the motor and meeting the requirements of 430.126(A) -(2) +* (3) Overtemperature protection relay utilizing thermal sensors embedded in the motor and meeting the requirements of 430.126(A)(2) * (4) Thermal sensor embedded in the motor whose communications are received and acted upon by an adjustable-speed drive system @@ -1983,9 +1976,8 @@ For multiple motor applications, individual motor overtemperature protection sha ### 430.128 Disconnecting Means. The disconnecting means shall be permitted to be in the incoming line to the conversion equipment and shall have a rating not less than 115 percent of the rated input current of the conversion unit. -430.130 Branch-Circuit Short-Circuit and Ground-Fault Protection for Single Motor Circuits Containing -Power Conversion Equipment. +### 430.130 Branch-Circuit Short-Circuit and Ground-Fault Protection for Single Motor Circuits Containing Power Conversion Equipment. #### 430.130(A) Circuits Containing Power Conversion Equipment. @@ -1993,9 +1985,7 @@ Circuits containing power conversion equipment shall be protected by a branch ci * (1) The rating and type of protection shall be determined by 430.52(C)(1), (C)(3), (C)(5), or (C)(6), using the full-load current rating of the motor load as determined by 430.6(A) or (B). -Exception to 1: The rating and type of protection shall be permitted to be determined by Table 430.52 using the power conversion equipment’s rated input current where the power conversion equipment is listed and marked “Suitable for Output - -Motor Conductor Protection.” +Exception to 1: The rating and type of protection shall be permitted to be determined by Table 430.52 using the power conversion equipment’s rated input current where the power conversion equipment is listed and marked “Suitable for Output Motor Conductor Protection.” > [!info] Informational Note No. 1: > Motor conductor branch circuit short-circuit and ground-fault protection from the power conversion equipment to the motor is provided by power conversion equipment that is listed and marked “Suitable for Output Motor @@ -2096,7 +2086,7 @@ The ultimate trip current of overcurrent (overload) relays or other motor-protec ### 430.227 Disconnecting Means. -The controller disconnecting means shall be lockable in accordance with 110.25. +The controller disconnecting means shall be lockable in accordance with [[nfpa-70_110_requirements#110.25 Lockable Disconnecting Means.|110.25]]. ## Part XII. Protection of Live Parts — All Voltages @@ -2190,7 +2180,7 @@ Instrument transformer secondaries and exposed non–current-carrying metal or o ## Part XIV. Tables -Table 430.247 Full-Load Current in Amperes, Direct-Current Motors +### Table 430.247 Full-Load Current in Amperes, Direct-Current Motors ^t247 The following values of full-load currents* are for motors running at base speed. @@ -2223,9 +2213,7 @@ Armature Voltage Rating* 200 — — — 675 330 294 *These are average dc quantities. -Table 430.248 Full-Load Currents in - -Amperes, Single-Phase AlternatingCurrent Motors +### Table 430.248 Full-Load Currents in Amperes, Single-Phase Alternating-Current Motors ^t248 The following values of full-load currents are for motors running at usual speeds and motors with normal torque characteristics. The voltages listed are rated motor voltages. The currents listed shall be permitted for system voltage ranges of 110 to 120 and 220 to 240 volts. @@ -2255,9 +2243,7 @@ Volts 71⁄2 80 46.0 44.0 40 10 100 57.5 55.0 50 -Table 430.249 Full-Load Current, Two-Phase - -Alternating-Current Motors (4-Wire) +### Table 430.249 Full-Load Current, Two-Phase Alternating-Current Motors (4-Wire) ^t249 The following values of full-load current are for motors running at speeds usual for belted motors and motors with normal torque characteristics. Current in the common conductor of a 2-phase, 3-wire system will be 1.41 times the value given. The voltages listed are rated motor voltages. The currents listed shall be permitted for system voltage ranges of @@ -2327,7 +2313,7 @@ Volts 150 — 312 156 125 32 200 — 416 208 167 43 -Table 430.250 Full-Load Current, Three-Phase Alternating-Current Motors +### Table 430.250 Full-Load Current, Three-Phase Alternating-Current Motors ^t250 The following values of full-load currents are typical for motors running at speeds usual for belted motors torque characteristics. The voltages listed are rated motor voltages. The currents listed shall be permitted ranges of 110 to 120, 220 to 240, 440 to 480, and 550 to 600 volts. @@ -2358,16 +2344,7 @@ Facto 75 — 221 211 192 96 77 20 155 78 *For 90 and 80 percent power factor, the figures shall be multiplied by 1.1 and 1.25, respectively. -Table 430.251(A) Conversion Table of SinglePhase - -Locked-Rotor Currents for Selection of - -Disconnecting Means and Controllers as - -Determined from Horsepower and Voltage Rating - -For use only with 430.110, 440.12, 440.41, and -455.8(C). +### Table 430.251(A) Conversion Table of Single-Phase Locked-Rotor Currents for Selection of Disconnecting Means and Controllers as Determined from Horsepower and Voltage Rating For use only with 430.110, 440.12, 440.41, and 455.8(C). ^t251a Rated @@ -2387,11 +2364,7 @@ Amperes, Single Phase 7½ 480 265 240 10 1000 332 300 -Table 430.251(B) Conversion Table of Polyphase Design B, C, and D Maximum Locked-Rotor Currents for - -Selection of Disconnecting Means and Controllers as Determined from Horsepower and Voltage Rating and Design Letter - -For use only with 430.110, 440.12, 440.41, and 455.8(C). +### Table 430.251(B) Conversion Table of Polyphase Design B, C, and D Maximum Locked-Rotor Currents for Selection of Disconnecting Means and Controllers as Determined from Horsepower and Voltage Rating and Design Letter For use only with 430.110, 440.12, 440.41, and 455.8(C). ^t251b Rated diff --git a/nfpa-70_440_hvac-equipment.md b/nfpa-70_440_hvac-equipment.md index 70adff2..4026517 100644 --- a/nfpa-70_440_hvac-equipment.md +++ b/nfpa-70_440_hvac-equipment.md @@ -6,7 +6,7 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: Article 440 Air-Conditioning and Refrigerating Equipment @@ -25,27 +25,41 @@ The definitions in this section shall apply only within this article. ##### Branch-Circuit Selection Current. -The value in amperes to be used instead of the rated-load current in determining the ratings of motor branch-circuit conductors, disconnecting means, controllers, and branch-circuit short-circuit and ground-fault protective devices wherever the running overload protective device permits a sustained current greater than the specified percentage of the rated-load current. The value of branch-circuit selection current will always be equal to or greater than the marked rated-load current. +The value in amperes to be used instead of the rated-load current +in determining the ratings of motor branch-circuit conductors, +disconnecting means, controllers, +and branch-circuit short-circuit and ground-fault protective devices +wherever the running overload protective device permits a sustained current +greater than the specified percentage of the rated-load current. +The value of branch-circuit selection current +will always be equal to or greater than the marked rated-load current. ##### Leakage-Current Detector-Interrupter (LCDI). -A device provided in a power supply cord or cord set that senses leakage current flowing between or from the cord conductors and interrupts the circuit at a predetermined level of leakage current. +A device provided in a power supply cord or cord set +that senses leakage current flowing between or from the cord conductors +and interrupts the circuit at a predetermined level of leakage current. ##### Rated-Load Current. -The current of a hermetic refrigerant motor-compressor resulting when it is operated at the rated load, rated voltage, and rated frequency of the equipment it serves. +The current of a hermetic refrigerant motor-compressor +resulting when it is operated at the rated load, +rated voltage, and rated frequency +of the equipment it serves. ### 440.3 Other Articles. #### 440.3(A) Article 430. These provisions are in addition to, or amendatory of, -the provisions of Article 430 and other articles in this Code, +the provisions of [[nfpa-70_430_motors|Article 430]] +and other articles in this Code, which apply except as modified in this article. #### 440.3(B) Articles 422, 424, or 430. -The rules of Articles 422, 424, or 430, as applicable, +The rules of Articles [[nfpa-70_422_appliances|422]], +[[nfpa-70_424|424]], or [[nfpa-70_430_motors|430]], as applicable, shall apply to air-conditioning and refrigerating equipment that does not incorporate a hermetic refrigerant motor-compressor. This equipment includes devices @@ -60,7 +74,7 @@ Equipment such as room air conditioners, household refrigerators and freezers, drinking water coolers, and beverage dispensers shall be considered appliances, -and Article 422 shall also apply. +and [[nfpa-70_422_appliances|Article 422]] shall also apply. #### 440.3(D) Other Applicable Articles. @@ -82,9 +96,18 @@ shall also comply with the applicable provisions of Table 440.3(D). #### 440.4(A) Hermetic Refrigerant Motor-Compressor Nameplate. -A hermetic refrigerant motor-compressor shall be provided with a nameplate that shall indicate the manufacturer's name, trademark, or symbol; identifying designation; phase; voltage; and frequency. -The rated-load current in amperes of the motor-compressor shall be marked by the equipment manufacturer on either or both the motor-compressor nameplate and the nameplate of the equipment in which the motor-compressor is used. -The locked-rotor current of each single-phase motor-compressor having a rated-load current of more than 9 amperes at 115 volts, or more than 4.5 amperes at 230 volts, and each polyphase motor-compressor shall be marked on the motor-compressor nameplate. +A hermetic refrigerant motor-compressor shall be provided with a nameplate +that shall indicate the manufacturer's name, trademark, or symbol; +identifying designation; phase; voltage; and frequency. +The rated-load current in amperes of the motor-compressor +shall be marked by the equipment manufacturer +on either or both the motor-compressor nameplate +and the nameplate of the equipment in which the motor-compressor is used. +The locked-rotor current +of each single-phase motor-compressor having a rated-load current +of more than 9 amperes at 115 volts, or more than 4.5 amperes at 230 volts, +and each polyphase motor-compressor +shall be marked on the motor-compressor nameplate. Where a thermal protector complying with 440.52(A)(2) and (B)(2) is used, the motor-compressor nameplate or the equipment nameplate shall be marked with the words "thermally protected." @@ -92,7 +115,7 @@ Where a protective system complying with 440.52(A)(4) and (B)(4) is used and is furnished with the equipment, the equipment nameplate shall be marked with the words, "thermally protected system." -Where a protective system complying with 440.52(A) (4) and (B)(4) is specified, +Where a protective system complying with 440.52(A)(4) and (B)(4) is specified, the equipment nameplate shall be appropriately marked. #### 440.4(B) Multimotor and Combination-Load Equipment. @@ -103,15 +126,21 @@ Multimotor and combination-load equipment shall be provided with a visible namep > Multimotor and combination-load equipment that is suitable under the provisions of this article for connection to a single 15- or 20-ampere, 120-volt, or a 15-ampere, 208- or 240-volt, single-phase branch circuit shall be permitted to be marked as a single load. > [!important] Exception No. 2: -> The minimum supply circuit conductor ampacity and the maximum rating of the branch-circuit short-circuit and groundfault protective device shall not be required to be marked on a room air conditioner complying with 440.62(A). +> The minimum supply circuit conductor ampacity and the maximum rating of the branch-circuit short-circuit and ground-fault protective device shall not be required to be marked on a room air conditioner complying with 440.62(A). > [!important] Exception No. 3: -> Multimotor and combination-load equipment used in one- and two-family dwellings or cord-and-attachment-plugconnected equipment shall not be required to be marked with a short-circuit current rating. +> Multimotor and combination-load equipment used in one- and two-family dwellings or cord-and-attachment-plug-connected equipment shall not be required to be marked with a short-circuit current rating. #### 440.4(C) Branch-Circuit Selection Current. -A hermetic refrigerant motor-compressor, or equipment containing such a compressor, having a protection system that is approved for use with the motor-compressor that it protects and that permits continuous current in excess of the specified percentage of nameplate rated-load current given in 440.52(B)(2) or (B)(4) shall also be marked with a branch-circuit selection current that complies with -440.52(B)(2) or (B)(4). This marking shall be provided by the equipment manufacturer and shall be on the nameplate(s) where the rated-load current(s) appears. +A hermetic refrigerant motor-compressor, or equipment containing such a compressor, +having a protection system that is approved for use with the motor-compressor that it protects +and that permits continuous current in excess of the specified percentage +of nameplate rated-load current given in 440.52(B)(2) or (B)(4) +shall also be marked with a branch-circuit selection current +that complies with 440.52(B)(2) or (B)(4). +This marking shall be provided by the equipment manufacturer +and shall be on the nameplate(s) where the rated-load current(s) appears. ### 440.5 Marking on Controllers. @@ -119,12 +148,22 @@ A controller shall be marked with the manufacturer's name, trademark, or symbol; ### 440.6 Ampacity and Rating. -The size of conductors for equipment covered by this article shall be selected from Table 310.16 through Table 310.19 or calculated in accordance with 310.14 as applicable. The required ampacity of conductors and rating of equipment shall be determined according to -440.6(A) and 440.6(B). +The size of conductors for equipment covered by this article +shall be selected from Table 310.16 through Table 310.19 +or calculated in accordance with 310.14 as applicable. +The required ampacity of conductors and rating of equipment +shall be determined according to 440.6(A) and 440.6(B). #### 440.6(A) Hermetic Refrigerant Motor-Compressor. -For a hermetic refrigerant motor-compressor, the rated-load current marked on the nameplate of the equipment in which the motorcompressor is employed shall be used in determining the rating or ampacity of the disconnecting means, the branch-circuit conductors, the controller, the branch-circuit short-circuit and ground-fault protection, and the separate motor overload protection. Where no ratedload current is shown on the equipment nameplate, the rated-load current shown on the compressor nameplate shall be used. +For a hermetic refrigerant motor-compressor, +the rated-load current marked on the nameplate of the equipment in which the motor compressor is employed +shall be used in determining the rating or ampacity of the disconnecting means, +the branch-circuit conductors, the controller, +the branch-circuit short-circuit and ground-fault protection, +and the separate motor overload protection. +Where no rated load current is shown on the equipment nameplate, +the rated-load current shown on the compressor nameplate shall be used. > [!important] Exception No. 1: > Where so marked, the branch-circuit selection current shall be used instead of the rated-load current to determine the rating or ampacity of the disconnecting means, the branch-circuit conductors, the controller, and the branch-circuit short-circuit and ground-fault protection. @@ -134,18 +173,32 @@ For a hermetic refrigerant motor-compressor, the rated-load current marked on th #### 440.6(B) Multimotor Equipment. -For multimotor equipment employing a shaded-pole or permanent split-capacitor-type fan or blower motor, the full-load current for such motor marked on the nameplate of the equipment in which the fan or blower motor is employed shall be used instead of the horsepower rating to determine the ampacity or rating of the disconnecting means, the branch-circuit conductors, the controller, the branch-circuit short-circuit and ground-fault protection, and the separate overload protection. This marking on the equipment nameplate shall not be less than the current marked on the fan or blower motor nameplate. +For multimotor equipment employing a shaded-pole +or permanent split-capacitor-type fan or blower motor, +the full-load current for such motor +marked on the nameplate of the equipment in which the fan or blower motor is employed +shall be used instead of the horsepower rating +to determine the ampacity or rating of the disconnecting means, +the branch-circuit conductors, the controller, +the branch-circuit short-circuit and ground-fault protection, +and the separate overload protection. +This marking on the equipment nameplate +shall not be less than the current marked on the fan or blower motor nameplate. ### 440.7 Highest Rated (Largest) Motor. -In determining compliance with this article and with 430.24, 430.53(B) and 430.53(C), and 430.62(A), the highest rated (largest) motor shall be considered to be the motor that has the highest rated-load current. Where two or more motors have the same highest ratedload current, only one of them shall be considered as the highest rated (largest) motor. For other than hermetic refrigerant motorcompressors, and fan or blower motors as covered in 440.6(B), the full-load current used to determine the highest rated motor shall be the equivalent value corresponding to the motor horsepower rating selected from Table 430.248, Table 430.249, or Table 430.250. +In determining compliance with this article and with 430.24, 430.53(B) and 430.53(C), and 430.62(A), the highest rated (largest) motor shall be considered to be the motor that has the highest rated-load current. Where two or more motors have the same highest rated load-current, only one of them shall be considered as the highest rated (largest) motor. For other than hermetic refrigerant motor-compressors, and fan or blower motors as covered in 440.6(B), the full-load current used to determine the highest rated motor shall be the equivalent value corresponding to the motor horsepower rating selected from Table 430.248, Table 430.249, or Table 430.250. > [!important] Exception: > Where so marked, the branch-circuit selection current shall be used instead of the rated-load current in determining the highest rated (largest) motor-compressor. ### 440.8 Single Machine. -An air-conditioning or refrigerating system shall be considered to be a single machine under the provisions of 430.87, Exception No. 1, and 430.112, Exception. The motors shall be permitted to be located remotely from each other. +An air-conditioning or refrigerating system +shall be considered to be a single machine +under the provisions of [[nfpa-70_430_motors#^87-ex1|430.87, Exception No. 1]], +and [[nfpa-70_430_motors#^112-ex|430.112, Exception]]. +The motors shall be permitted to be located remotely from each other. ### 440.9 Grounding and Bonding. @@ -155,7 +208,7 @@ Where equipment is installed outdoors on a roof, an equipment grounding conducto #### 440.10(A) Installation. -Motor controllers or industrial control panels of multimotor and combination-load equipment shall not be installed where the available fault current exceeds its short-circuit current rating as marked in accordance with 440.4(B). +Motor controllers or industrial control panels of multimotor and combination-load equipment shall not be installed where the available fault current exceeds its short-circuit current rating as marked in accordance with [[#440.4(B) Multimotor and Combination-Load Equipment.|440.4(B)]]. #### 440.10(B) Documentation. @@ -175,28 +228,42 @@ A disconnecting means serving a hermetic refrigerant motor-compressor shall be s ##### 440.12(A)(1) Ampere Rating. -The ampere rating shall be at least 115 percent of the nameplate rated-load current or branch-circuit selection current, whichever is greater. +The ampere rating shall be at least 115 percent of +the nameplate rated-load current +or branch-circuit selection current, +whichever is greater. > [!important] Exception: > A listed unfused motor circuit switch, without fuseholders, having a horsepower rating not less than the equivalent horsepower determined in accordance with 440.12(A)(2) shall be permitted to have an ampere rating less than 115 percent of the specified current. ##### 440.12(A)(2) Equivalent Horsepower. -To determine the equivalent horsepower in complying with the requirements of 430.109, the horsepower rating shall be selected from - -Table 430.248, Table 430.249, or Table 430.250 corresponding to the rated-load current or branch-circuit selection current, whichever is greater, and also the horsepower rating from Table 430.251(A) or Table 430.251(B) corresponding to the locked-rotor current. In case the nameplate rated-load current or branch-circuit selection current and locked-rotor current do not correspond to the currents shown in - -Table 430.248, Table 430.249, Table 430.250, Table 430.251(A), or Table 430.251(B), the horsepower rating corresponding to the next higher value shall be selected. In case different horsepower ratings are obtained when applying these tables, a horsepower rating at least equal to the larger of the values obtained shall be selected. +To determine the equivalent horsepower +in complying with the requirements of [[nfpa-70_430_motors#430.109 Type.|430.109]], +the horsepower rating shall be selected from +[[nfpa-70_430_motors#^t248|Table 430.248]], +[[nfpa-70_430_motors#^t249|Table 430.249]], +or [[nfpa-70_430_motors#^t250|Table 430.250]] +corresponding to the rated-load current or branch-circuit selection current, whichever is greater, +and also the horsepower rating from [[nfpa-70_430_motors#^t251a|Table 430.251(A)]] +or [[nfpa-70_430_motors#^t251b|Table 430.251(B)]] +corresponding to the locked-rotor current. +In case the nameplate rated-load current or branch-circuit selection current and locked-rotor current +do not correspond to the currents shown in Table 430.248, Table 430.249, +Table 430.250, Table 430.251(A), or Table 430.251(B), +the horsepower rating corresponding to the next higher value shall be selected. +In case different horsepower ratings are obtained when applying these tables, +a horsepower rating at least equal to the larger of the values obtained shall be selected. #### 440.12(B) Combination Loads. -Where the combined load of two or more hermetic refrigerant motor-compressors or one or more hermetic refrigerant motorcompressor with other motors or loads may be simultaneous on a single disconnecting means, the rating for the disconnecting means shall be determined in accordance with 440.12(B)(1) and (B)(2). +Where the combined load of two or more hermetic refrigerant motor-compressors or one or more hermetic refrigerant motor-compressor with other motors or loads may be simultaneous on a single disconnecting means, the rating for the disconnecting means shall be determined in accordance with 440.12(B)(1) and (B)(2). ##### 440.12(B)(1) Horsepower Rating. -The horsepower rating of the disconnecting means shall be determined from the sum of all currents, including resistance loads, at the rated-load condition and also at the locked-rotor condition. The combined rated-load current and the combined locked-rotor current so obtained shall be considered as a single motor for the purpose of this requirement as required by 440.12(B)(1)(a) and (B) (1) (b). +The horsepower rating of the disconnecting means shall be determined from the sum of all currents, including resistance loads, at the rated-load condition and also at the locked-rotor condition. The combined rated-load current and the combined locked-rotor current so obtained shall be considered as a single motor for the purpose of this requirement as required by 440.12(B)(1)(a) and (B)(1)(b). -* (a) The full-load current equivalent to the horsepower rating of each motor, other than a hermetic refrigerant motor-compressor, and fan or blower motors as covered in 440.6(B) shall be selected from Table 430.248, Table 430.249, or Table 430.250. These fullload currents shall be added to the motor-compressor rated-load current(s) or branch-circuit selection current(s), whichever is greater, and to the rating in amperes of other loads to obtain an equivalent full-load current for the combined load. +* (a) The full-load current equivalent to the horsepower rating of each motor, other than a hermetic refrigerant motor-compressor, and fan or blower motors as covered in 440.6(B) shall be selected from Table 430.248, Table 430.249, or Table 430.250. These full-load currents shall be added to the motor-compressor rated-load current(s) or branch-circuit selection current(s), whichever is greater, and to the rating in amperes of other loads to obtain an equivalent full-load current for the combined load. * (b) The locked-rotor current equivalent to the horsepower rating of each motor, other than a hermetic refrigerant motor-compressor, shall be selected from Table 430.251(A) or Table 430.251(B), and, for fan and blower motors of the shaded-pole or permanent split-capacitor type marked with the locked-rotor current, the marked value shall be used. The locked-rotor currents shall be added to the motor-compressor locked-rotor current(s) and to the rating in amperes of other loads to obtain an equivalent locked-rotor current for the combined load. Where two or more motors or other loads such as resistance heaters, or both, cannot be started simultaneously, appropriate combinations of locked-rotor and rated-load current or branch-circuit selection current, whichever is greater, shall be an acceptable means of determining the equivalent locked-rotor current for the simultaneous combined load. @@ -205,15 +272,15 @@ The horsepower rating of the disconnecting means shall be determined from the su ##### 440.12(B)(2) Full-Load Current Equivalent. -The ampere rating of the disconnecting means shall be at least 115 percent of the sum of all currents at the rated-load condition determined in accordance with 440.12(B)(1). +The ampere rating of the disconnecting means shall be at least 115 percent +of the sum of all currents at the rated-load condition determined in accordance with 440.12(B)(1). > [!important] Exception: > A listed unfused motor circuit switch, without fuseholders, having a horsepower rating not less than the equivalent horsepower determined by 440.12(B)(1) shall be permitted to have an ampere rating less than 115 percent of the sum of all currents. #### 440.12(C) Small Motor-Compressors. -For small motor-compressors not having the locked-rotor current marked on the nameplate, or for small motors not covered by Table -430.247, Table 430.248, Table 430.249, or Table 430.250, the locked-rotor current shall be assumed to be six times the rated-load current. +For small motor-compressors not having the locked-rotor current marked on the nameplate, or for small motors not covered by Table 430.247, Table 430.248, Table 430.249, or Table 430.250, the locked-rotor current shall be assumed to be six times the rated-load current. #### 440.12(D) Disconnecting Means. diff --git a/nfpa-70_450_transformers.md b/nfpa-70_450_transformers.md index 019da8b..754d551 100644 --- a/nfpa-70_450_transformers.md +++ b/nfpa-70_450_transformers.md @@ -51,7 +51,7 @@ This article also covers the installation of transformers in hazardous (classifi The definitions in this section shall apply only within this article. -Transformer. +#### Transformer. An individual transformer, single or polyphase, identified by a single nameplate, unless otherwise indicated in this article. @@ -76,7 +76,7 @@ Overcurrent protection shall be provided in accordance with Table 450.3(B). > [!important] Exception: > Where the transformer is installed as a motor control circuit transformer in accordance with 430.72(C)(1) through (C)(5). -Table 450.3(A) Maximum Rating or Setting of Overcurrent Protection for Transformers Over 1000 Volts +##### Table 450.3(A) Maximum Rating or Setting of Overcurrent Protection for Transformers Over 1000 Volts (as a Percentage of Transformer-Rated Current) %% TODO %% @@ -94,7 +94,7 @@ Notes: 4. A transformer equipped with a coordinated thermal overload protection by the manufacturer shall be permitted to have separate secondary protection omitted. -Table 450.3(B) Maximum Rating or Setting of Overcurrent Protection for Transformers 1000 Volts and Less (as a Percentage of Transformer-Rated Current) +##### Table 450.3(B) Maximum Rating or Setting of Overcurrent Protection for Transformers 1000 Volts and Less (as a Percentage of Transformer-Rated Current) %% TODO %% @@ -341,16 +341,16 @@ Transformers, other than Class 2 or Class 3 transformers, shall have a disconnec ### 450.21 Dry-Type Transformers Installed Indoors. -#### 450.21(A) Not Over 1121⁄ 2 kVA. +#### 450.21(A) Not Over 112 1⁄2 kVA. Dry-type transformers installed indoors and rated 1121⁄ 2 kVA or less shall have a separation of at least 300 mm (12 in.) from combustible material unless separated from the combustible material by a fire-resistant, heat-insulated barrier. > [!important] Exception: > This rule shall not apply to transformers rated for 1000 volts, nominal, or less that are completely enclosed, except for ventilating openings. -#### 450.21(B) Over 1121⁄ 2 kVA. +#### 450.21(B) Over 112 1⁄2 kVA. -Individual dry-type transformers of more than 1121⁄ 2 kVA rating shall be installed in a transformer room of fire-resistant construction having a minimum fire rating of 1 hour. +Individual dry-type transformers of more than 112 1⁄2 kVA rating shall be installed in a transformer room of fire-resistant construction having a minimum fire rating of 1 hour. > [!important] Exception No. 1: > Transformers with Class 155 or higher insulation systems and separated from combustible material by a fire-resistant, heat-insulating barrier or by not less than 1.83 m (6 ft) horizontally and 3.7 m (12 ft) vertically. @@ -369,7 +369,7 @@ Dry-type transformers rated over 35,000 volts shall be installed in a vault comp Dry-type transformers installed outdoors shall have a weatherproof enclosure. -Transformers exceeding 1121⁄ 2 kVA shall not be located within 300 mm (12 in.) of combustible materials of buildings unless the transformer has Class 155 insulation systems or higher and is completely enclosed except for ventilating openings. +Transformers exceeding 112 1⁄2 kVA shall not be located within 300 mm (12 in.) of combustible materials of buildings unless the transformer has Class 155 insulation systems or higher and is completely enclosed except for ventilating openings. ### 450.23 Less-Flammable Liquid-Insulated Transformers. @@ -451,7 +451,7 @@ Oil-insulated transformers installed indoors shall be installed in a vault const * (2) Safe egress is provided for personnel. -* (3) A minimum 6-mm (1⁄ 4-in.) steel barrier is provided for personnel protection. +* (3) A minimum 6-mm (1⁄4-in.) steel barrier is provided for personnel protection. ### 450.27 Oil-Insulated Transformers Installed Outdoors. diff --git a/nfpa-70_700_emergency-systems.md b/nfpa-70_700_emergency-systems.md index cfd7676..a8bd74b 100644 --- a/nfpa-70_700_emergency-systems.md +++ b/nfpa-70_700_emergency-systems.md @@ -6,7 +6,7 @@ tags: - authorship/other - destiny/uncertain - exclude-from-word-count - - status/incomplete + - status/draft - topic/construction/electrical - type/media title: Article 700 Emergency Systems diff --git a/nfpa-70_725_control-circuits.md b/nfpa-70_725_control-circuits.md index 40b5991..d195e0b 100644 --- a/nfpa-70_725_control-circuits.md +++ b/nfpa-70_725_control-circuits.md @@ -9,9 +9,9 @@ tags: - status/incomplete - topic/construction/electrical - type/media -title: NEC Article 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits +title: Article 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits --- -# NEC Article 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits +# Article 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits ## Part I. General @@ -27,6 +27,8 @@ materials. The definitions in this section shall apply only within this article. +%% TODO %% + ## Part III. Class 2 and Class 3 Circuits ### 725.136 Separation from Electric Light, Power, Class 1, Non--Power-Limited Fire Alarm Circuit diff --git a/nfpa-70_dump_wiring-methods.md b/nfpa-70_dump_wiring-methods.md new file mode 100644 index 0000000..e586de5 --- /dev/null +++ b/nfpa-70_dump_wiring-methods.md @@ -0,0 +1,6293 @@ +--- +id: +aliases: [] +tags: + - authorship/other + - destiny/fleeting + - exclude-from-word-count + - status/incomplete + - topic/construction/electrical + - type/media +title: Article 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits +--- +# NEC Chapter 3 Wiring Methods Articles Dump + +# Article 320 Armored Cable: Type AC + +## Part I. General + +### 320.1 Scope. + +This article covers the use, installation, and construction specifications for armored cable, Type AC. + +### 320.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Armored Cable, Type AC. + +A fabricated assembly of insulated conductors in a flexible interlocked metallic armor. See 320.100. + +### 320.6 Listing Requirements. + +Type AC cable and associated fittings shall be listed. + +## Part II. Installation + +### 320.10 Uses Permitted. + +Type AC cable shall be permitted as follows: + +* (1) For feeders and branch circuits in both exposed and concealed installations + +* (2) In cable trays + +* (3) In dry locations + +* (4) Embedded in plaster finish on brick or other masonry, except in damp or wet locations + +* (5) To be run or fished in the air voids of masonry block or tile walls where such walls are not exposed or subject to excessive moisture or dampness + +> [!info] Informational Note: +> The “Uses Permitted” is not an all-inclusive list. + +### 320.12 Uses Not Permitted. + +Type AC cable shall not be used as follows: + +* (1) Where subject to physical damage + +* (2) In damp or wet locations + +* (3) In air voids of masonry block or tile walls where such walls are exposed or subject to excessive moisture or dampness + +* (4) Where exposed to corrosive conditions + +* (5) Embedded in plaster finish on brick or other masonry in damp or wet locations + +### 320.15 Exposed Work. + +Exposed runs of cable, except as provided in 300.11(B), shall closely follow the surface of the building finish or of running boards. + +Exposed runs shall also be permitted to be installed on the underside of joists where supported at each joist and located so as not to be subject to physical damage. + +### 320.17 Through or Parallel to Framing Members. + +Type AC cable shall be protected in accordance with 300.4(A), (C), and (D) where installed through or parallel to framing members. + +### 320.23 In Accessible Attics. + +Type AC cables in accessible attics or roof spaces shall be installed as specified in 320.23(A) and (B). + +#### 320.23(A) Cables Run Across the Top of Floor Joists. + +Where run across the top of floor joists, or within 2.1 m (7 ft) of the floor or floor joists across the face of rafters or studding, the cable shall be protected by guard strips that are at least as high as the cable. Where this space is not accessible by permanently installed stairs or ladders, protection shall only be required within 1.8 m (6 ft) of the nearest edge of the scuttle hole or attic entrance. + +#### 320.23(B) Cable Installed Parallel to Framing Members. + +Where the cable is installed parallel to the sides of rafters, studs, or ceiling or floor joists, neither guard strips nor running boards shall be required, and the installation shall also comply with 300.4(D). + +### 320.24 Bending Radius. + +Bends in Type AC cable shall be made such that the cable is not damaged. The radius of the curve of the inner edge of any bend shall not be less than five times the diameter of the Type AC cable. + +### 320.30 Securing and Supporting. + +#### 320.30(A) General. + +Type AC cable shall be supported and secured by staples; cable ties listed and identified for securement and support; straps, hangers, or similar fittings; or other approved means designed and installed so as not to damage the cable. + +#### 320.30(B) Securing. + +Unless otherwise permitted, Type AC cable shall be secured within 300 mm (12 in.) of every outlet box, junction box, cabinet, or fitting and at intervals not exceeding 1.4 m (41⁄2 ft). + +#### 320.30(C) Supporting. + +Unless otherwise permitted, Type AC cable shall be supported at intervals not exceeding 1.4 m (41⁄2 ft). + +Horizontal runs of Type AC cable installed in wooden or metal framing members or similar supporting means shall be considered supported and secured where such support does not exceed 1.4 m (41⁄2 ft) intervals. + +#### 320.30(D) Unsupported Cables. + +Type AC cable shall be permitted to be unsupported and unsecured where the cable complies with any of the following: + +* (1) Is fished between access points through concealed spaces in finished buildings or structures and supporting is impracticable + +* (2) Is not more than 600 mm (2 ft) in length at terminals where flexibility is necessary + +* (3) Is not more than 1.8 m (6 ft) in length from the last point of cable support to the point of connection to a luminaire(s) or other electrical equipment and the cable and point of connection are within an accessible ceiling + +For the purposes of this section, Type AC cable fittings shall be permitted as a means of cable support. + +### 320.40 Boxes and Fittings. + +At all points where the armor of AC cable terminates, a fitting shall be provided to protect wires from abrasion, unless the design of the outlet boxes or fittings is such as to afford equivalent protection, and, in addition, an insulating bushing or its equivalent protection shall be provided between the conductors and the armor. The connector or clamp by which the Type AC cable is fastened to boxes or cabinets shall be of such design that the insulating bushing or its equivalent will be visible for inspection. Where change is made from + +Type AC cable to other cable or raceway wiring methods, a box, fitting, or conduit body shall be installed at junction points as required in 300.15. + +### 320.80 Ampacity. + +The ampacity shall be determined in accordance with 310.14. + +#### 320.80(A) Thermal Insulation. + +Armored cable installed in thermal insulation shall have conductors rated at 90°C (194°F). The ampacity of cable installed in these applications shall not exceed that of a 60°C (140°F) rated conductor. The 90°C (194°F) rating shall be permitted to be used for ampacity adjustment and correction calculations; however, the ampacity shall not exceed that of a 60°C (140°F) rated conductor. + +Where more than two Type AC cables containing two or more current-carrying conductors in each cable are installed in contact with thermal insulation, caulk, or sealing foam without maintaining spacing between cables, the ampacity of each conductor shall be adjusted in accordance with Table 310.15(C)(1). + +#### 320.80(B) Cable Tray. + +The ampacity of Type AC cable installed in cable tray shall be determined in accordance with 392.80(A). + +## Part III. Construction Specifications + +### 320.100 Construction. + +Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length. + +### 320.104 Conductors. + +Insulated conductors shall be of a type listed in Table 310.4(A) or those identified for use in this cable. In addition, the conductors shall have an overall moisture-resistant and fire-retardant fibrous covering. For Type ACT, a moisture-resistant fibrous covering shall be required only on the individual conductors. + +### 320.108 Equipment Grounding Conductor. + +Type AC cable shall provide an adequate path for fault current as required by 250.4(A)(5) or (B)(4) to act as an equipment grounding conductor. + +### 320.120 Marking. + +The cable shall be marked in accordance with 310.8, except that Type AC shall have ready identification of the manufacturer by distinctive external markings on the cable armor throughout its entire length. + +# Article 322 Flat Cable Assemblies: Type FC + +## Part I. General + +### 322.1 Scope. + +This article covers the use, installation, and construction specifications for flat cable assemblies, Type FC. + +### 322.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Flat Cable Assembly, Type FC. + +An assembly of parallel conductors formed integrally with an insulating material web specifically designed for field installation in surface metal raceway. + +### 322.6 Listing Requirements. + +Type FC and associated fittings shall be listed. + +## Part II. Installation + +### 322.10 Uses Permitted. + +Flat cable assemblies shall be permitted only as follows: + +* (1) As branch circuits to supply suitable tap devices for lighting, small appliances, or small power loads. The rating of the branch circuit shall not exceed 30 amperes. + +* (2) Where installed for exposed work. + +* (3) In locations where they will not be subjected to physical damage. Where a flat cable assembly is installed less than 2.5 m (8 ft) above the floor or fixed working platform, it shall be protected by a cover identified for the use. + +* (4) In surface metal raceways identified for the use. The channel portion of the surface metal raceway systems shall be installed as complete systems before the flat cable assemblies are pulled into the raceways. + +### 322.12 Uses Not Permitted. + +Flat cable assemblies shall not be used as follows: + +* (1) Where exposed to corrosive conditions, unless suitable for the application + +* (2) In hoistways or on elevators or escalators + +* (3) In any hazardous (classified) location, except as specifically permitted by other articles in this Code + +* (4) Outdoors or in wet or damp locations unless identified for the use + +### 322.30 Securing and Supporting. + +The flat cable assemblies shall be supported by means of their special design features, within the surface metal raceways. + +The surface metal raceways shall be supported as required for the specific raceway to be installed. + +### 322.40 Boxes and Fittings. + +#### 322.40(A) Dead Ends. + +Each flat cable assembly dead end shall be terminated in an end-cap device identified for the use. + +The dead-end fitting for the enclosing surface metal raceway shall be identified for the use. + +#### 322.40(B) Luminaire Hangers. + +Luminaire hangers installed with the flat cable assemblies shall be identified for the use. + +#### 322.40(C) Fittings. + +Fittings to be installed with flat cable assemblies shall be designed and installed to prevent physical damage to the cable assemblies. + +#### 322.40(D) Extensions. + +All extensions from flat cable assemblies shall be made by approved wiring methods, within the junction boxes, installed at either end of the flat cable assembly runs. + +### 322.56 Splices and Taps. + +#### 322.56(A) Splices. + +Splices shall be made in listed junction boxes. + +#### 322.56(B) Taps. + +Taps shall be made between any phase conductor and the grounded conductor or any other phase conductor by means of devices and fittings identified for the use. Tap devices shall be rated at not less than 15 amperes, or more than 300 volts to ground, and shall be color-coded in accordance with the requirements of 322.120(C). + +## Part III. Construction Specifications + +### 322.100 Construction. + +Flat cable assemblies shall consist of two, three, four, or five conductors. + +### 322.104 Conductors. + +Flat cable assemblies shall have conductors of 10 AWG special stranded copper wires. + +### 322.112 Insulation. + +The entire flat cable assembly shall be formed to provide a suitable insulation covering all the conductors and using one of the materials recognized in Table 310.4(A) for general branch-circuit wiring. + +### 322.120 Marking. + +#### 322.120(A) Temperature Rating. + +In addition to the provisions of 310.8, Type FC cable shall have the temperature rating durably marked on the surface at intervals not exceeding 600 mm (24 in.). + +#### 322.120(B) Identification of Grounded Conductor. + +The grounded conductor shall be identified throughout its length by means of a distinctive and durable white or gray marking. + +> [!info] Informational Note: +> The color gray may have been used in the past as an ungrounded conductor. Care should be taken when working on existing systems. + +#### 322.120(C) Terminal Block Identification. + +Terminal blocks identified for the use shall have distinctive and durable markings for color or word coding. The grounded conductor section shall have a white marking or other suitable designation. The next adjacent section of the terminal block shall have a black marking or other suitable designation. The next section shall have a red marking or other suitable designation. The final or outer section, opposite the grounded conductor section of the terminal block, shall have a blue marking or other suitable designation. + +# Article 324 Flat Conductor Cable: Type FCC + +## Part I. General + +### 324.1 Scope. + +This article covers a field-installed wiring system for branch circuits incorporating Type FCC cable and associated accessories as defined by the article. The wiring system is designed for installation under carpet squares. + +### 324.2 Definitions. + +The definitions in this section shall apply only within this article. + +Bottom Shield. + +A protective layer that is installed between the floor and Type FCC flat conductor cable to protect the cable from physical damage and may or may not be incorporated as an integral part of the cable. + +Cable Connector. + +A connector designed to join Type FCC cables without using a junction box. + +FCC System. + +A complete wiring system for branch circuits that is designed for installation under carpet squares. + +> [!info] Informational Note: +> The FCC system includes Type FCC cable and associated shielding, connectors, terminators, adapters, boxes, and receptacles. + +Insulating End. + +An insulator designed to electrically insulate the end of a Type FCC cable. + +Metal Shield Connections. + +Means of connection designed to electrically and mechanically connect a metal shield to another metal shield, to a receptacle housing or self-contained device, or to a transition assembly. + +Top Shield. + +A grounded metal shield covering under-carpet components of the FCC system for the purposes of providing protection against physical damage. + +Transition Assembly. + +An assembly to facilitate connection of the FCC system to other wiring systems, incorporating (1) a means of electrical interconnection and (2) a suitable box or covering for providing electrical safety and protection against physical damage. + +Type FCC Cable. + +Three or more flat copper conductors placed edge-to-edge and separated and enclosed within an insulating assembly. + +### 324.6 Listing Requirements. + +Type FCC cable and associated fittings shall be listed. + +## Part II. Installation + +### 324.10 Uses Permitted. + +#### 324.10(A) Branch Circuits. + +Use of FCC systems shall be permitted both for general-purpose and appliance branch circuits and for individual branch circuits. + +#### 324.10(B) Branch-Circuit Ratings. + +##### 324.10(B)(1) Voltage. + +Voltage between ungrounded conductors shall not exceed 300 volts. Voltage between ungrounded conductors and the grounded conductor shall not exceed 150 volts. + +##### 324.10(B)(2) Current. + +General-purpose and appliance branch circuits shall have ratings not exceeding 20 amperes. Individual branch circuits shall have ratings not exceeding 30 amperes. + +#### 324.10(C) Floors. + +Use of FCC systems shall be permitted on hard, sound, smooth, continuous floor surfaces made of concrete, ceramic, or composition flooring, wood, and similar materials. + +#### 324.10(D) Walls. + +Use of FCC systems shall be permitted on wall surfaces in surface metal raceways. + +#### 324.10(E) Damp Locations. + +Use of FCC systems in damp locations shall be permitted. + +#### 324.10(F) Heated Floors. + +Materials used for floors heated in excess of 30°C (86°F) shall be identified as suitable for use at these temperatures. + +#### 324.10(G) System Height. + +Any portion of an FCC system with a height above floor level exceeding 2.3 mm (0.090 in.) shall be tapered or feathered at the edges to floor level. + +### 324.12 Uses Not Permitted. + +FCC systems shall not be used in the following locations: + +* (1) Outdoors or in wet locations + +* (2) Where subject to corrosive vapors + +* (3) In any hazardous (classified) location + +* (4) In residential buildings + +* (5) In school and hospital buildings, other than administrative office areas + +### 324.18 Crossings. + +Crossings of more than two Type FCC cable runs shall not be permitted at any one point. Crossings of a Type FCC cable over or under a flat communications or signal cable shall be permitted. In each case, a grounded layer of metal shielding shall separate the two cables, and crossings of more than two flat cables shall not be permitted at any one point. + +### 324.30 Securing and Supporting. + +All FCC system components shall be firmly anchored to the floor or wall using an adhesive or mechanical anchoring system identified for this use. Floors shall be prepared to ensure adherence of the FCC system to the floor until the carpet squares are placed. + +### 324.40 Boxes and Fittings. + +#### 324.40(A) Cable Connections and Insulating Ends. + +All Type FCC cable connections shall use connectors identified for their use, installed such that electrical continuity, insulation, and sealing against dampness and liquid spillage are provided. All bare cable ends shall be insulated and sealed against dampness and liquid spillage using listed insulating ends. + +#### 324.40(B) Polarization of Connections. + +All receptacles and connections shall be constructed and installed so as to maintain proper polarization of the system. + +#### 324.40(C) Shields. + +##### 324.40(C)(1) Top Shield. + +A metal top shield shall be installed over all floor-mounted Type FCC cable, connectors, and insulating ends. The top shield shall completely cover all cable runs, corners, connectors, and ends. + +##### 324.40(C)(2) Bottom Shield. + +A bottom shield shall be installed beneath all Type FCC cable, connectors, and insulating ends. + +#### 324.40(D) Connection to Other Systems. + +Power feed, grounding connection, and shield system connection between the FCC system and other wiring systems shall be accomplished in a transition assembly identified for this use. + +#### 324.40(E) Metal-Shield Connectors. + +Metal shields shall be connected to each other and to boxes, receptacle housings, self-contained devices, and transition assemblies using metal-shield connectors. + +### 324.41 Floor Coverings. + +Floor-mounted Type FCC cable, cable connectors, and insulating ends shall be covered with carpet squares not larger than 1.0 m +(39.37 in.) square. Carpet squares that are adhered to the floor shall be attached with release-type adhesives. + +### 324.42 Devices. + +#### 324.42(A) Receptacles. + +All receptacles, receptacle housings, and self-contained devices used with the FCC system shall be identified for this use and shall be connected to the Type FCC cable and metal shields. Connection from any equipment grounding conductor of the Type FCC cable shall be made to the shield system at each receptacle. + +#### 324.42(B) Receptacles and Housings. + +Receptacle housings and self-contained devices designed either for floor mounting or for in-wall or on-wall mounting shall be permitted for use with the FCC system. Receptacle housings and self-contained devices shall incorporate means for facilitating entry and termination of Type FCC cable and for electrically connecting the housing or device with the metal shield. Receptacles and selfcontained devices shall comply with 406.4. Power and communications outlets installed together in common housing shall be permitted in accordance with 805.133(A)(1)(c), Exception No. 2. + +### 324.56 Splices and Taps. + +#### 324.56(A) FCC Systems Alterations. + +Alterations to FCC systems shall be permitted. New cable connectors shall be used at new connection points to make alterations. It shall be permitted to leave unused cable runs and associated cable connectors in place and energized. All cable ends shall be covered with insulating ends. + +#### 324.56(B) Transition Assemblies. + +All transition assemblies shall be identified for their use. Each assembly shall incorporate means for facilitating entry of the Type FCC cable into the assembly, for connecting the Type FCC cable to grounded conductors, and for electrically connecting the assembly to the metal cable shields and to equipment grounding conductors. + +### 324.60 Grounding and Bonding. + +All metal shields, boxes, receptacle housings, and self-contained devices shall be electrically continuous to the equipment grounding conductor of the supplying branch circuit. All such electrical connections shall be made with connectors identified for this use. The electrical resistivity of such shield system shall not be more than that of one conductor of the Type FCC cable used in the installation. + +## Part III. Construction Specifications + +### 324.100 Construction. + +#### 324.100(A) Type FCC Cable. + +Type FCC cable shall be listed for use with the FCC system and shall consist of three, four, or five flat copper conductors, one of which shall be an equipment grounding conductor. + +#### 324.100(B) Shields. + +##### 324.100(B)(1) Materials and Dimensions. + +All top and bottom shields shall be of designs and materials identified for their use. Top shields shall be metal. Both metallic and nonmetallic materials shall be permitted for bottom shields. + +##### 324.100(B)(2) Resistivity. + +Metal shields shall have cross-sectional areas that provide for electrical resistivity of not more than that of one conductor of the Type + +FCC cable used in the installation. + +### 324.101 Corrosion Resistance. + +Metal components of the system shall be either corrosion resistant, coated with corrosion-resistant materials, or insulated from contact with corrosive substances. + +### 324.112 Insulation. + +The insulating material of the cable shall be moisture resistant and flame retardant. All insulating materials in the FCC systems shall be identified for their use. + +### 324.120 Markings. + +#### 324.120(A) Cable Marking. + +Type FCC cable shall be clearly and durably marked on both sides at intervals of not more than 610 mm (24 in.) with the information required by 310.8(A) and with the following additional information: + +* (1) Material of conductors + +* (2) Maximum temperature rating + +* (3) Ampacity + +#### 324.120(B) Conductor Identification. + +Conductors shall be clearly and durably identified on both sides throughout their length as specified in 310.6. + +# Article 326 Integrated Gas Spacer Cable: Type IGS + +## Part I. General + +### 326.1 Scope. + +This article covers the use, installation, and construction specifications for integrated gas spacer cable, Type IGS. + +### 326.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Integrated Gas Spacer Cable, Type IGS. + +A factory assembly of one or more conductors, each individually insulated and enclosed in a loose fit, nonmetallic flexible conduit as an integrated gas spacer cable rated 0 volts through 600 volts. + +## Part II. Installation + +### 326.10 Uses Permitted. + +Type IGS cable shall be permitted for use underground, including direct burial in the earth, as the following: + +* (1) Service-entrance conductors + +* (2) Feeder or branch-circuit conductors + +* (3) Service conductors, underground + +### 326.12 Uses Not Permitted. + +Type IGS cable shall not be used as interior wiring or be exposed in contact with buildings. + +### 326.24 Bending Radius. + +Where the coilable nonmetallic conduit and cable are bent for installation purposes or are flexed or bent during shipment or installation, the radius of the curve of the inner edge measured to the inside of the bend shall not be less than specified in Table 326.24. + +Table 326.24 Minimum Radii of Bends + +Conduit Size Minimum Radii + +Metric Designator Trade Size mm in. + +Conduit Size Minimum Radii + +Metric Designator Trade Size mm in. +53 2 600 24 +78 3 900 35 +103 4 1150 45 + +### 326.26 Bends. + +A run of Type IGS cable between pull boxes or terminations shall not contain more than the equivalent of four quarter bends (360 degrees total), including those bends located immediately at the pull box or terminations. + +### 326.40 Fittings. + +Terminations and splices for Type IGS cable shall be identified as a type that is suitable for maintaining the gas pressure within the conduit. A valve and cap shall be provided for each length of the cable and conduit to check the gas pressure or to inject gas into the conduit. + +### 326.80 Ampacity. + +The ampacity of Type IGS cable shall not exceed the values shown in Table 326.80. + +Table 326.80 Ampacity of Type IGS Cable + +Size (kcmil) Amperes Size (kcmil) Amperes +250 119 2500 376 +500 168 3000 412 +750 206 3250 429 +1000 238 3500 445 +1250 266 3750 461 +1500 292 4000 476 +1750 315 4250 491 +2000 336 4500 505 +2250 357 4750 519 + +## Part III. Construction Specifications + +### 326.104 Conductors. + +The conductors shall be solid aluminum rods, laid parallel, consisting of one to nineteen 12.7 mm (1⁄2 in.) diameter rods. The minimum conductor size shall be 250 kcmil, and the maximum size shall be 4750 kcmil. + +### 326.112 Insulation. + +The insulation shall be dry kraft paper tapes and a pressurized sulfur hexafluoride gas (SF ), both approved for electrical use. The nominal gas pressure shall be 138 kPa gauge (20 lb/in. gauge). The thickness of the paper spacer shall be as specified in Table +326.112. + +Table 326.112 Paper + +Spacer Thickness + +Size (kcmil) + +Thickness mm in. +250–1000 1.02 0.040 +1250–4750 1.52 0.060 + +### 326.116 Conduit. + +6 +2 + +The conduit shall be a medium density polyethylene identified as suitable for use with natural gas rated pipe in metric designator 53, 78, or 103 (trade size 2, 3, or 4). The percent fill dimensions for the conduit are shown in Table 326.116. + +The size of the conduit permitted for each conductor size shall be calculated for a percent fill not to exceed those found in Table 1, + +Chapter 9. + +Table 326.116 Conduit Dimensions + +Conduit Size Actual Outside Diameter Actual Inside Diameter + +Metric Designator Trade Size mm in. mm in. +53 2 60 2.375 49.46 1.947 +78 3 89 3.500 73.30 2.886 +103 4 114 4.500 94.23 3.710 + +### 326.120 Marking. + +The cable shall be marked in accordance with 310.8(A), 310.8(B)(1), and 310.8(D). + +# Article 336 Power and Control Tray Cable: Type TC + +## Part I. General + +### 336.1 Scope. + +This article covers the use, installation, and construction specifications for power and control tray cable, Type TC. + +### 336.2 Definition. + +The definition in this section shall apply within this article and throughout this Code. + +Power and Control Tray Cable, Type TC. + +A factory assembly of two or more insulated conductors, with or without associated bare or covered equipment grounding conductors, under a nonmetallic jacket. + +### 336.6 Listing Requirements. + +Type TC cables and associated fittings shall be listed. + +## Part II. Installation + +### 336.10 Uses Permitted. + +Type TC cable shall be permitted to be used as follows: + +* (1) For power, lighting, control, and signal circuits. + +* (2) In cable trays, including those with mechanically discontinuous segments up to 300 mm (1 ft). + +* (3) In raceways. + +* (4) In outdoor locations supported by a messenger wire. + +* (5) For Class 1 circuits as permitted in Parts II and III of Article 725. + +* (6) For non-power-limited fire alarm circuits if conductors comply with the requirements of 760.49. + +* (7) Between a cable tray and the utilization equipment or device(s), provided all of the following apply: + * a. The cable is Type TC-ER. + * b. The cable is installed in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation. + * c. The cable is continuously supported and protected against physical damage using mechanical protection such as struts, angles, or channels. + * d. The cable complies with the crush and impact requirements of Type MC cable and is identified with the marking “TC– + +ER.” + * e. The cable is secured at intervals not exceeding 1.8 m (6 ft). + * f. Equipment grounding for the utilization equipment is provided by an equipment grounding conductor within the cable. In cables containing conductors sized 6 AWG or smaller, the equipment grounding conductor shall be provided within the cable or, at the time of installation, one or more insulated conductors shall be permanently identified as an equipment grounding conductor in accordance with 250.119(B). + +Exception to (7): Where not subject to physical damage, Type TC-ER shall be permitted to transition between cable trays and between cable trays and equipment or devices for a distance not to exceed 1.8 m (6 ft) without continuous support. The cable shall be mechanically supported where exiting the cable tray to ensure that the minimum bending radius is not exceeded. + +* (8) Type TC cable shall be resistant to moisture and corrosive agents where installed in wet locations. + +* (9) In one- and two-family dwelling units, Type TC-ER-JP cable containing both power and control conductors shall be permitted for branch circuits and feeders. Type TC-ER-JP cable used as interior wiring shall be installed per the requirements of Part II of + +Article 334 and where installed as exterior wiring shall be installed per the requirements of Part II of Article 340. + +> [!important] Exception: +> Where used to connect a generator and associated equipment having terminals rated 75°C (140°F) or higher, the cable shall not be limited in ampacity by 334.80 or 340.80. + +> [!info] Informational Note: +> See 725.136 for limitations on Class 2 or 3 circuits contained within the same cable with conductors of electric light, power, or Class 1 circuits. + +* (10) Direct buried, where identified for such use. + +* (11) In hazardous (classified) locations where specifically permitted by other articles in this Code. + +> [!info] Informational Note: +> See 310.14(A)(3) for temperature limitation of conductors. + +### 336.12 Uses Not Permitted. + +Type TC tray cable shall not be installed or used as follows: + +* (1) Installed where it will be exposed to physical damage + +* (2) Installed outside a raceway or cable tray system, except as permitted in 336.10(4), 336.10(7), 336.10(9), and 336.10(10) + +* (3) Used where exposed to direct rays of the sun, unless identified as sunlight resistant + +### 336.24 Bending Radius. + +Bends in Type TC cable shall be made so as not to damage the cable. For Type TC cable without metal shielding, the minimum bending radius shall be as follows: + +* (1) Four times the overall diameter for cables 25 mm (1 in.) or less in diameter + +* (2) Five times the overall diameter for cables larger than 25 mm (1 in.) but not more than 50 mm (2 in.) in diameter + +* (3) Six times the overall diameter for cables larger than 50 mm (2 in.) in diameter + +Type TC cables with metallic shielding shall have a minimum bending radius of not less than 12 times the cable overall diameter. + +### 336.80 Ampacity. + +The ampacity of Type TC tray cable shall be determined in accordance with 392.80(A) for 14 AWG and larger conductors, in accordance with 402.5 for 18 AWG through 16 AWG conductors where installed in cable trays, and in accordance with 310.14 where installed outside of cable trays, where permitted. + +## Part III. Construction Specifications + +### 336.100 Construction. + +A metallic sheath or armor as defined in 330.116 shall not be permitted either under or over the nonmetallic jacket. Metallic shield(s) shall be permitted over groups of conductors, under the outer jacket, or both. + +### 336.104 Conductors. + +For ungrounded, grounded, and equipment grounding conductors, the conductor sizes shall be 14 AWG through 1000 kcmil copper, nickel, or nickel-coated copper and 12 AWG through 1000 kcmil aluminum or copper-clad aluminum. Insulation types shall be one of the types listed in Table 310.4(A) or Table 310.4(B) that is suitable for branch circuit and feeder circuits or one that is identified for such use. + +For control and signal conductors, the minimum conductor sizes shall be 18 AWG copper, nickel, or nickel-coated copper, 14 AWG copper-clad aluminum, and 12 AWG aluminum. + +#### 336.104(A) Fire Alarm Systems. + +Where used for fire alarm systems, conductors shall also be in accordance with 760.49. + +#### 336.104(B) Thermocouple Circuits. + +Conductors in Type TC cable used for thermocouple circuits in accordance with Part III of Article 725 shall also be permitted to be any of the materials used for thermocouple extension wire. + +#### 336.104(C) Class 1 Circuit Conductors. + +Insulated conductors of 18 AWG and 16 AWG copper shall also be in accordance with 725.49. + +### 336.116 Jacket. + +The outer jacket shall be a flame-retardant, nonmetallic material. + +### 336.120 Marking. + +There shall be no voltage marking on a Type TC cable employing thermocouple extension wire. + +### 336.130 Hazardous (Classified) Location Cable. + +Cable listed and marked Type TC-ER-HL shall comply with the following: + +* (1) The overall nonmetallic jacket shall be suitable for the environment. + +* (2) The overall cable construction shall be essentially circular in cross-section. + +* (3) The overall nonmetallic jacket shall be continuous and gas/vapor tight. + +* (4) For construction greater than 25.4 mm (1 in.) in diameter, the following shall apply: + * a. The equipment grounding conductor shall be bare. + * b. A metallic shield shall be included over all conductors under the outer jacket. + +# Article 337 Type P Cable + +## Part I. General + +### 337.1 Scope. + +This article covers the use, installation, and construction specifications for up through 2000 volt Type P cable (armored and unarmored). + +### 337.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Type P. Cable + +A factory assembly of one or more insulated flexible tinned copper conductors, with associated equipment grounding conductor(s), with or without a braided metallic armor and with an overall nonmetallic jacket. + +### 337.6 Listing Requirements. + +Type P cables and associated fittings shall be listed. + +## Part II. Installation + +### 337.10 Uses Permitted. + +Type P cable shall be permitted to be used: + +* (1) Under engineering supervision in industrial installations where conditions of maintenance and supervision ensure that only qualified persons monitor and service the system. + +* (2) In hazardous (classified) locations where specifically permitted by other articles in this Code. + +### 337.12 Uses Not Permitted. + +Type P cable shall not be installed or used: + +* (1) Where it will be exposed to physical damage + +* (2) Where not specifically permitted by other articles in the Code + +### 337.24 Bending Radius. + +The minimum bending radii during installations and handling in service shall be adequate to prevent damage to the cable. + +### 337.30 Securing and Supporting. + +Type P cable shall be supported and secured by cable ties listed and identified for securement and support; straps, hangers, or similar fittings; or other approved means designed and installed so as not to damage the cable. + +### 337.31 Single Conductors. + +Where single-conductor cables are used, the installation shall comply with 300.20. + +### 337.80 Ampacity. + +The ampacity of Type P cable shall be determined in accordance with 310.14(A) or 310.14(B) for 14 AWG and larger conductors. For +18 AWG and 16 AWG conductors the ampacities shall be determined in accordance with Table 402.5. When installed in cable tray, the ampacities shall be permitted to be determined in accordance with 392.80. The installation shall not exceed the temperature ratings of terminations and equipment. + +## Part III. Construction Specifications + +### 337.104 Conductors. + +Conductors shall be of tinned copper. Conductors shall employ flexible stranding. The minimum conductor size shall be 18 AWG. + +### 337.108 Equipment Grounding Conductor. + +An equipment grounding conductor complying with 250.122 shall be provided within the cable. + +### 337.112 Insulation. + +Insulated conductors shall be a thermoset type identified for use in Type P cable. All conductors shall be suitable for wet locations. The minimum wall thickness shall be 0.76 mm (30 mils). + +### 337.114 Shield. + +Metallic shield(s) shall be permitted over a single conductor or groups of conductors. + +### 337.115 Jacket. + +Single conductor cables and multiconductor cables shall have an overall nonmetallic jacket that is impervious to moisture, corrosion resistant, and sunlight resistant. + +### 337.116 Armor. + +Armor shall be permitted over the jacket. If provided, the armor or metallic covering shall be a braided basket weave type consisting of wire laid closely together, flat and parallel, and forming a basket weave that shall firmly grip the cable. The wire shall be commercial bronze. The armor shall not be used as a current-carrying conductor or as an equipment grounding conductor. A nonmetallic jacket that conforms to 337.115 shall be provided over the armor. + +### 337.120 Marking. + +Type P cable shall be marked in accordance with 310.8. When an armor is provided, the cable shall be marked accordingly. + +# Article 338 Service-Entrance Cable: Types SE and USE + +## Part I. General + +### 338.1 Scope. + +This article covers the use, installation, and construction specifications of service-entrance cable. + +### 338.2 Definitions. + +The definition in this section shall apply within this article and throughout the Code. + +Service-Entrance Cable. + +A single conductor or multiconductor cable provided with an overall covering, primarily used for services, and of the following types: + +Type SE. + +Service-entrance cable having a flame-retardant, moisture-resistant covering. + +Type USE. + +Service-entrance cable, identified for underground use, having a moisture-resistant covering, but not required to have a flame-retardant covering. + +Service-Entrance Conductor Assembly. + +Multiple single-insulated conductors twisted together without an overall covering, other than an optional binder intended only to keep the conductors together. + +### 338.6 Listing Requirements. + +Type SE and USE cables and associated fittings shall be listed. + +## Part II. Installation + +### 338.10 Uses Permitted. + +#### 338.10(A) Service-Entrance Conductors. + +Service-entrance cable shall be permitted to be used as service-entrance conductors and shall be installed in accordance with 230.6, +230.7, and Parts II, III, and IV of Article 230. + +#### 338.10(B) Branch Circuits or Feeders. + +##### 338.10(B)(1) Grounded Conductor Insulated. + +Type SE service-entrance cables shall be permitted in wiring systems where all of the circuit conductors of the cable are of the thermoset or thermoplastic type. + +##### 338.10(B)(2) Use of Uninsulated Conductor. + +Type SE service-entrance cable shall be permitted for use where the insulated conductors are used for circuit wiring and the uninsulated conductor is used only for equipment grounding purposes. + +> [!important] Exception: +> In existing installations, uninsulated conductors shall be permitted as a grounded conductor in accordance with 250.32 and +250.140, where the uninsulated grounded conductor of the cable originates in service equipment, and with 225.30 through 225.40. + +##### 338.10(B)(3) Temperature Limitations. + +Type SE service-entrance cable used to supply appliances shall not be subject to conductor temperatures in excess of the temperature specified for the type of insulation involved. + +##### 338.10(B)(4) Installation Methods for Branch Circuits and Feeders. + +> [!info] Informational Note No. 1: +> See 310.14(A)(3) for temperature limitation of conductors. + +> [!info] Informational Note No. 2: +> For the installation of main power feeder conductors in dwelling units refer to 310.12. + +* (a) Interior Installations. + +* (1) In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Part II of Article 334, excluding 334.80. + +* (2) Where more than two Type SE cables containing two or more current-carrying conductors in each cable are installed in contact with thermal insulation, caulk, or sealing foam without maintaining spacing between cables, the ampacity of each conductor shall be adjusted in accordance with Table 310.15(C)(1). + +* (3) For Type SE cable with ungrounded conductor sizes 10 AWG and smaller, where installed in contact with thermal insulation, the ampacity shall be in accordance with 60°C (140°F) conductor temperature rating. The maximum conductor temperature rating shall be permitted to be used for ampacity adjustment and correction purposes, if the final ampacity does not exceed that for a 60°C (140°F) rated conductor. + +* (b) Exterior Installations. + +* (1) In addition to the provisions of this article, service-entrance cable used for feeders or branch circuits, where installed as exterior wiring, shall be installed in accordance with Part I of Article 225. The cable shall be supported in accordance with +334.30. + +* (2) Type USE cable installed as underground feeder and branch circuit cable shall comply with Part II of Article 340. + +> [!important] Exception: +> Single-conductor Type USE and multi-rated USE conductors shall not be subject to the ampacity limitations of Part II of + +Article 340. + +### 338.12 Uses Not Permitted. + +#### 338.12(A) Service-Entrance Cable. + +Service-entrance cable (SE) shall not be used under the following conditions or in the following locations: + +* (1) Where subject to physical damage unless protected in accordance with 230.50(B) + +* (2) Underground with or without a raceway + +* (3) For exterior branch circuits and feeder wiring unless the installation complies with the provisions of Part I of Article 225 and is supported in accordance with 334.30 or is used as messenger-supported wiring as permitted in Part II of Article 396 + +#### 338.12(B) Underground Service-Entrance Cable. + +Underground service-entrance cable (USE) shall not be used under the following conditions or in the following locations: + +* (1) For interior wiring + +* (2) For aboveground installations except where USE cable emerges from the ground and is terminated in an enclosure at an outdoor location and the cable is protected in accordance with 300.5(D) + +* (3) As aerial cable unless it is a multiconductor cable identified for use aboveground and installed as messenger-supported wiring in accordance with 225.10 and Part II of Article 396 + +### 338.24 Bending Radius. + +Bends in Types USE and SE cable shall be so made that the cable will not be damaged. The radius of the curve of the inner edge of any bend, during or after installation, shall not be less than five times the diameter of the cable. + +## Part III. Construction Specifications + +### 338.100 Construction. + +#### 338.100(A) Assemblies. + +Cabled assemblies of multiple single-conductor Type USE conductors shall be permitted for direct burial. All conductors shall be insulated. + +> [!info] Informational Note: +> The term “cabled” refers to a manufacturing process of twisting single conductors together and may also be referred to as “plexed.” + +#### 338.100(B) Uninsulated Conductor. + +Type SE or USE cable with an overall covering containing two or more conductors shall be permitted to have one conductor uninsulated. + +### 338.120 Marking. + +Service-entrance cable shall be marked as required in 310.8. Cable with the neutral conductor smaller than the ungrounded conductors shall be so marked. + +# Article 340 Underground Feeder and Branch-Circuit Cable: Type UF + +## Part I. General + +### 340.1 Scope. + +This article covers the use, installation, and construction specifications for underground feeder and branch-circuit cable, Type UF. + +### 340.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Underground Feeder and Branch-Circuit Cable, Type UF. + +A factory assembly of one or more insulated conductors with an integral or an overall covering of nonmetallic material suitable for direct burial in the earth. + +### 340.6 Listing Requirements. + +Type UF cable and associated fittings shall be listed. + +## Part II. Installation + +### 340.10 Uses Permitted. + +Type UF cable shall be permitted as follows: + +* (1) For use underground, including direct burial in the earth. + +* (2) As single-conductor cables. Where installed as single-conductor cables, all conductors of the feeder or branch circuit, including the grounded conductor and equipment grounding conductor, if any, shall be installed in accordance with 300.3. + +* (3) For wiring in wet, dry, or corrosive locations. + +* (4) Installed as nonmetallic-sheathed cable. Where so installed, the installation and conductor requirements shall comply with Parts + +II and III of Article 334 and shall be of the multiconductor type. + +* (5) As single-conductor cables as the nonheating leads for heating cables as provided in 424.43. + +* (6) Supported by cable trays. Type UF cable supported by cable trays shall be of the multiconductor type. + +> [!info] Informational Note: +> See 310.14(A)(3) for temperature limitation of conductors. + +### 340.12 Uses Not Permitted. + +Type UF cable shall not be used as follows: + +* (1) As service-entrance cable + +* (2) In commercial garages + +* (3) In theaters and similar locations + +* (4) In motion picture studios + +* (5) In storage battery rooms + +* (6) In hoistways or on elevators or escalators + +* (7) In hazardous (classified) locations, except as specifically permitted by other articles in this Code + +* (8) Embedded in poured cement, concrete, or aggregate, except where embedded in plaster as nonheating leads where permitted in 424.43 + +* (9) Where exposed to direct rays of the sun, unless identified as sunlight resistant + +> [!info] Informational Note: +> The sunlight-resistant marking on the jacket does not apply to the individual conductors. + +* (10) Where subject to physical damage + +* (11) As overhead cable, except where installed as messenger-supported wiring in accordance with Part II of Article 396 + +### 340.24 Bending Radius. + +Bends in Type UF cable shall be so made that the cable is not damaged. The radius of the curve of the inner edge of any bend shall not be less than five times the diameter of the cable. + +### 340.80 Ampacity. + +The ampacity of Type UF cable shall be that of 60°C (140°F) conductors in accordance with 310.14. + +## Part III. Construction Specifications + +### 340.104 Conductors. + +The conductors shall be sizes 14 AWG copper or 12 AWG aluminum or copper-clad aluminum through 4/0 AWG. + +### 340.108 Equipment Grounding Conductor. + +In addition to the insulated conductors, the cable shall be permitted to have an insulated or bare equipment grounding conductor. + +### 340.112 Insulation. + +The conductors of Type UF shall be one of the moisture-resistant types listed in Table 310.4(A) that is suitable for branch-circuit wiring or one that is identified for such use. Where installed as a substitute wiring method for NM cable, the conductor insulation shall be rated +90°C (194°F). + +### 340.116 Sheath. + +The overall covering shall be flame retardant; moisture, fungus, and corrosion resistant; and suitable for direct burial in the earth. + +# Article 342 Intermediate Metal Conduit: Type IMC + +## Part I. General + +### 342.1 Scope. + +This article covers the use, installation, and construction specifications for intermediate metal conduit (IMC) and associated fittings. + +### 342.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Intermediate Metal Conduit (IMC). + +A steel threadable raceway of circular cross section designed for the physical protection and routing of conductors and cables and for use as an equipment grounding conductor when installed with its integral or associated coupling and appropriate fittings. + +### 342.6 Listing Requirements. + +IMC, factory elbows and couplings, and associated fittings shall be listed. + +## Part II. Installation + +### 342.10 Uses Permitted. + +#### 342.10(A) All Atmospheric Conditions and Occupancies. + +Use of IMC shall be permitted under all atmospheric conditions and occupancies. + +#### 342.10(B) Corrosion Environments. + +IMC, elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection approved for the condition. + +#### 342.10(C) Cinder Fill. + +IMC shall be permitted to be installed in or under cinder fill where subject to permanent moisture where protected on all sides by a layer of noncinder concrete not less than 50 mm (2 in.) thick; where the conduit is not less than 450 mm (18 in.) under the fill; or where protected by corrosion protection approved for the condition. + +#### 342.10(D) Wet Locations. + +All supports, bolts, straps, screws, and so forth, shall be of corrosion-resistant materials or protected against corrosion by corrosionresistant materials. + +> [!info] Informational Note: +> See 300.6 for protection against corrosion. + +#### 342.10(E) Severe Physical Damage. + +IMC shall be permitted to be installed where subject to severe physical damage. + +### 342.14 Dissimilar Metals. + +Where practicable, dissimilar metals in contact anywhere in the system shall be avoided to eliminate the possibility of galvanic action. + +Stainless steel and aluminum fittings and enclosures shall be permitted to be used with galvanized steel IMC where not subject to severe corrosive influences. + +Stainless steel IMC shall only be used with the following: + +* (1) Stainless steel fittings + +* (2) Stainless steel boxes and enclosures + +* (3) Steel (galvanized, painted, powder or PVC coated, and so forth) boxes and enclosures when not subject to severe corrosive influences + +* (4) Stainless steel, nonmetallic, or approved accessories + +### 342.20 Size. + +#### 342.20(A) Minimum. + +IMC smaller than metric designator 16 (trade size 1⁄2) shall not be used. + +#### 342.20(B) Maximum. + +IMC larger than metric designator 103 (trade size 4) shall not be used. + +> [!info] Informational Note: +> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions. + +### 342.22 Number of Conductors. + +The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. + +Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +### 342.24 Bends — How Made. + +Bends of IMC shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. The radius of the curve of any field bend to the centerline of the conduit shall not be less than indicated in Table 2, Chapter 9. + +### 342.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. + +### 342.28 Reaming and Threading. + +All cut ends shall be reamed or otherwise finished to remove rough edges. Where conduit is threaded in the field, a standard cutting die with a taper of 1 in 16 (3⁄4 in. taper per foot) shall be used. + +> [!info] Informational Note: +> See ANSI/ASME B1.20.1-2013, Standard for Pipe Threads, General Purpose (Inch). + +### 342.30 Securing and Supporting. + +IMC shall be installed as a complete system in accordance with 300.18 and shall be securely fastened in place and supported in accordance with 342.30(A) and (B). + +#### 342.30(A) Securely Fastened. + +IMC shall be secured in accordance with one of the following: + +* (1) IMC shall be securely fastened within 900 mm (3 ft) of each outlet box, junction box, device box, cabinet, conduit body, or other conduit termination. + +* (2) Where structural members do not readily permit fastening within 900 mm (3 ft), fastening shall be permitted to be increased to a distance of 1.5 m (5 ft). + +* (3) Where approved, conduit shall not be required to be securely fastened within 900 mm (3 ft) of the service head for above-theroof termination of a mast. + +#### 342.30(B) Supports. + +IMC shall be supported in accordance with one of the following: + +* (1) Conduit shall be supported at intervals not exceeding 3 m (10 ft). + +* (2) The distance between supports for straight runs of conduit shall be permitted in accordance with Table 344.30(B)(2), provided the conduit is made up with threaded couplings and supports that prevent transmission of stresses to termination where conduit is deflected between supports. + +* (3) Exposed vertical risers from industrial machinery or fixed equipment shall be permitted to be supported at intervals not exceeding 6 m (20 ft) if the conduit is made up with threaded couplings, the conduit is supported and securely fastened at the top and bottom of the riser, and no other means of intermediate support is readily available. + +* (4) Horizontal runs of IMC supported by openings through framing members at intervals not exceeding 3 m (10 ft) and securely fastened within 900 mm (3 ft) of termination points shall be permitted. + +### 342.42 Couplings and Connectors. + +#### 342.42(A) Threadless. + +Threadless couplings and connectors used with conduit shall be made tight. Where buried in masonry or concrete, they shall be the concretetight type. Where installed in wet locations, they shall comply with 314.15. Threadless couplings and connectors shall not be used on threaded conduit ends unless listed for the purpose. + +#### 342.42(B) Running Threads. + +Running threads shall not be used on conduit for connection at couplings. + +### 342.46 Bushings. + +Where a conduit enters a box, fitting, or other enclosure, a bushing shall be provided to protect the wires from abrasion unless the box, fitting, or enclosure is designed to provide such protection. + +> [!info] Informational Note: +> See 300.4(G) for the protection of conductors 4 AWG and larger at bushings. + +### 342.56 Splices and Taps. + +Splices and taps shall be made in accordance with 300.15. + +### 342.60 Grounding. + +IMC shall be permitted as an equipment grounding conductor. + +## Part III. Construction Specifications + +### 342.100 Construction. + +IMC shall be made of one of the following: + +* (1) Steel, with protective coatings + +* (2) Stainless steel + +### 342.120 Marking. + +Each length shall be clearly and durably marked at least every 1.5 m (5 ft) with the letters IMC. Each length shall be marked as required in the first sentence of 110.21(A). + +# Article 344 Rigid Metal Conduit: Type RMC + +## Part I. General + +### 344.1 Scope. + +This article covers the use, installation, and construction specifications for rigid metal conduit (RMC) and associated fittings. + +### 344.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Rigid Metal Conduit (RMC). + +A threadable raceway of circular cross section designed for the physical protection and routing of conductors and cables and for use as an equipment grounding conductor when installed with its integral or associated coupling and appropriate fittings. + +### 344.6 Listing Requirements. + +RMC, factory elbows and couplings, and associated fittings shall be listed. + +## Part II. Installation + +### 344.10 Uses Permitted. + +#### 344.10(A) Atmospheric Conditions and Occupancies. + +##### 344.10(A)(1) Galvanized Steel, Stainless Steel, and Red Brass RMC. + +Galvanized steel, stainless steel, and red brass RMC shall be permitted under all atmospheric conditions and occupancies. + +##### 344.10(A)(2) Aluminum RMC. + +Aluminum RMC shall be permitted to be installed where approved for the environment. Rigid aluminum conduit encased in concrete or in direct contact with the earth shall be provided with approved supplementary corrosion protection. + +##### 344.10(A)(3) Ferrous Raceways and Fittings. + +Ferrous raceways and fittings protected from corrosion solely by enamel shall be permitted only indoors and in occupancies not subject to severe corrosive influences. + +#### 344.10(B) Corrosive Environments. + +##### 344.10(B)(1) Galvanized Steel, Stainless Steel, and Red Brass RMC, Elbows, Couplings, and Fittings. + +Galvanized steel, stainless steel, and red brass RMC elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection approved for the condition. + +##### 344.10(B)(2) Supplementary Protection of Aluminum RMC. + +Aluminum RMC shall be provided with approved supplementary corrosion protection where encased in concrete or in direct contact with the earth. + +#### 344.10(C) Cinder Fill. + +Galvanized steel, stainless steel, and red brass RMC shall be permitted to be installed in or under cinder fill where subject to permanent moisture where protected on all sides by a layer of noncinder concrete not less than 50 mm (2 in.) thick; where the conduit is not less than 450 mm (18 in.) under the fill; or where protected by corrosion protection approved for the condition. + +#### 344.10(D) Wet Locations. + +All supports, bolts, straps, screws, and so forth, shall be of corrosion-resistant materials or protected against corrosion by corrosionresistant materials. + +> [!info] Informational Note: +> See 300.6 for protection against corrosion. + +#### 344.10(E) Severe Physical Damage. + +RMC shall be permitted to be installed where subject to severe physical damage. + +### 344.14 Dissimilar Metals. + +Where practicable, dissimilar metals in contact anywhere in the system shall be avoided to eliminate the possibility of galvanic action. + +Stainless steel and aluminum fittings and enclosures shall be permitted to be used with galvanized steel RMC, and galvanized steel fittings and enclosures shall be permitted to be used with aluminum RMC where not subject to severe corrosive influences. Stainless steel rigid conduit shall only be used with the following: + +* (1) Stainless steel fittings + +* (2) Stainless steel boxes and enclosures + +* (3) Steel (galvanized, painted, powder or PVC coated, and so forth) boxes and enclosures when not subject to severe corrosive influences + +* (4) Stainless steel, nonmetallic, or approved accessories + +### 344.20 Size. + +#### 344.20(A) Minimum. + +RMC smaller than metric designator 16 (trade size 1⁄2) shall not be used. + +> [!important] Exception: +> For enclosing the leads of motors as permitted in 430.245(B). + +#### 344.20(B) Maximum. + +RMC larger than metric designator 155 (trade size 6) shall not be used. + +> [!info] Informational Note: +> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions. + +### 344.22 Number of Conductors. + +The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. + +Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +### 344.24 Bends — How Made. + +Bends of RMC shall be so made that the conduit will not be damaged and so that the internal diameter of the conduit will not be effectively reduced. The radius of the curve of any field bend to the centerline of the conduit shall not be less than indicated in Table 2, + +Chapter 9. + +### 344.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. + +### 344.28 Reaming and Threading. + +All cut ends shall be reamed or otherwise finished to remove rough edges. Where conduit is threaded in the field, a standard cutting die with a 1 in 16 taper (3⁄4 in. taper per foot) shall be used. + +> [!info] Informational Note: +> See ANSI/ASME B1.20.1-2013, Standard for Pipe Threads, General Purpose (Inch). + +### 344.30 Securing and Supporting. + +RMC shall be installed as a complete system in accordance with 300.18 and shall be securely fastened in place and supported in accordance with 344.30(A) and (B). + +#### 344.30(A) Securely Fastened. + +RMC shall be secured in accordance with one of the following: + +* (1) RMC shall be securely fastened within 900 mm (3 ft) of each outlet box, junction box, device box, cabinet, conduit body, or other conduit termination. + +* (2) Fastening shall be permitted to be increased to a distance of 1.5 m (5 ft) where structural members do not readily permit fastening within 900 mm (3 ft). + +* (3) Where approved, conduit shall not be required to be securely fastened within 900 mm (3 ft) of the service head for above-theroof termination of a mast. + +#### 344.30(B) Supports. + +RMC shall be supported in accordance with one of the following: + +* (1) Conduit shall be supported at intervals not exceeding 3 m (10 ft). + +* (2) The distance between supports for straight runs of conduit shall be permitted in accordance with Table 344.30(B)(2), provided the conduit is made up with threaded couplings and supports that prevent transmission of stresses to termination where conduit is deflected between supports. + +* (3) Exposed vertical risers from industrial machinery or fixed equipment shall be permitted to be supported at intervals not exceeding 6 m (20 ft) if the conduit is made up with threaded couplings, the conduit is supported and securely fastened at the top and bottom of the riser, and no other means of intermediate support is readily available. + +* (4) Horizontal runs of RMC supported by openings through framing members at intervals not exceeding 3 m (10 ft) and securely fastened within 900 mm (3 ft) of termination points shall be permitted. + +Table 344.30(B)(2) Supports for Rigid Metal Conduit + +Conduit Size Maximum Distance Between Rigid Metal Conduit Supports + +Metric Designator Trade Size m ft +16–21 1⁄2–3⁄4 3.0 10 +27 1 3.7 12 +35–41 11⁄4–11⁄2 4.3 14 +53–63 2–21⁄2 4.9 16 +78 and larger 3 and larger 6.1 20 + +### 344.42 Couplings and Connectors. + +#### 344.42(A) Threadless. + +Threadless couplings and connectors used with conduit shall be made tight. Where buried in masonry or concrete, they shall be the concrete tight type. Where installed in wet locations, they shall comply with 314.15. Threadless couplings and connectors shall not be used on threaded conduit ends unless listed for the purpose. + +#### 344.42(B) Running Threads. + +Running threads shall not be used on conduit for connection at couplings. + +### 344.46 Bushings. + +Where a conduit enters a box, fitting, or other enclosure, a bushing shall be provided to protect the wires from abrasion unless the box, fitting, or enclosure is designed to provide such protection. + +> [!info] Informational Note: +> See 300.4(G) for the protection of conductors sizes 4 AWG and larger at bushings. + +### 344.56 Splices and Taps. + +Splices and taps shall be made in accordance with 300.15. + +### 344.60 Grounding. + +RMC shall be permitted as an equipment grounding conductor. + +## Part III. Construction Specifications + +### 344.100 Construction. + +RMC shall be made of one of the following: + +* (1) Steel with protective coatings + +* (2) Aluminum + +* (3) Red brass + +* (4) Stainless steel + +### 344.120 Marking. + +Each length shall be clearly and durably identified in every 3 m (10 ft) as required in the first sentence of 110.21(A). Nonferrous conduit of corrosion-resistant material shall have suitable markings. + +# Article 348 Flexible Metal Conduit: Type FMC + +## Part I. General + +### 348.1 Scope. + +This article covers the use, installation, and construction specifications for flexible metal conduit (FMC) and associated fittings. + +### 348.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Flexible Metal Conduit (FMC). + +A raceway of circular cross section made of helically wound, formed, interlocked metal strip. + +### 348.6 Listing Requirements. + +FMC and associated fittings shall be listed. + +## Part II. Installation + +### 348.10 Uses Permitted. + +FMC shall be permitted to be used in exposed and concealed locations. + +### 348.12 Uses Not Permitted. + +FMC shall not be used in the following: + +* (1) In wet locations + +* (2) In hoistways, other than as permitted in 620.21(A)(1) + +* (3) In storage battery rooms + +* (4) In any hazardous (classified) location except as permitted by other articles in this Code + +* (5) Where exposed to materials having a deteriorating effect on the installed conductors, such as oil or gasoline + +* (6) Underground or embedded in poured concrete or aggregate + +* (7) Where subject to physical damage + +### 348.20 Size. + +#### 348.20(A) Minimum. + +FMC less than metric designator 16 (trade size 1⁄2) shall not be used unless permitted in 348.20(A)(1) through (A)(5) for metric designator 12 (trade size 3⁄8). + +* (1) For enclosing the leads of motors as permitted in 430.245(B) + +* (2) In lengths not in excess of 1.8 m (6 ft) for any of the following uses: + * a. For utilization equipment + * b. As part of a listed assembly + * c. For tap connections to luminaires as permitted in 410.117(C) + +* (3) For manufactured wiring systems as permitted in 604.100(A) + +* (4) In hoistways as permitted in 620.21(A)(1) + +* (5) As part of a listed assembly to connect wired luminaire sections as permitted in 410.137(C) + +#### 348.20(B) Maximum. + +FMC larger than metric designator 103 (trade size 4) shall not be used. + +> [!info] Informational Note: +> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions. + +### 348.22 Number of Conductors. + +The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9, or as permitted in Table +348.22, or for metric designator 12 (trade size 3⁄8). + +Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +Table 348.22 Maximum Number of Insulated Conductors in Metric Designator 12 (Trade Size 3⁄8) Flexible + +Metal Conduit (FMC) + +Size +(AWG) + +Types RFH-2, SF-2 Types TF, XHHW, TW + +Types TFN, THHN, + +THWN + +Types FEP, FEBP, PF, + +PGF + +Fittings + +Inside + +Conduit + +Fittings + +Outside + +Conduit + +Fittings + +Inside + +Conduit + +Fittings + +Outside + +Conduit + +Fittings + +Inside + +Conduit + +Fittings + +Outside + +Conduit + +Fittings + +Inside + +Conduit + +Fittings + +Outside + +Conduit +18 2 3 3 5 5 8 5 8 +16 1 2 3 4 4 6 4 6 +14 1 2 2 3 3 4 3 4 +12 — — 1 2 2 3 2 3 +10 — — 1 1 1 1 1 2 +*In addition, one insulated, covered, or bare equipment grounding conductor of the same size shall be permitted. + +### 348.24 Bends — How Made. + +Bends in conduit shall be made so that the conduit is not damaged and the internal diameter of the conduit is not effectively reduced. + +Bends shall be permitted to be made manually without auxiliary equipment. The radius of the curve to the centerline of any bend shall not be less than shown in Table 2, Chapter 9 using the column “Other Bends.” + +### 348.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. + +### 348.28 Trimming. + +All cut ends shall be trimmed or otherwise finished to remove rough edges, except where fittings that thread into the convolutions are used. + +### 348.30 Securing and Supporting. + +FMC shall be securely fastened in place and supported in accordance with 348.30(A) and (B). + +#### 348.30(A) Securely Fastened. + +* + +FMC shall be securely fastened in place by an approved means within 300 mm (12 in.) of each box, cabinet, conduit body, or other conduit termination and shall be supported and secured at intervals not to exceed 1.4 m (41⁄2 ft). Where used, cable ties shall be listed and be identified for securement and support. + +> [!important] Exception No. 1: +> Where FMC is fished between access points through concealed spaces in finished buildings or structures and supporting is impracticable. + +> [!important] Exception No. 2: +> Where flexibility is necessary after installation, lengths from the last point where the raceway is securely fastened shall not exceed the following: + +* (1) 900 mm (3 ft) for metric designators 16 through 35 (trade sizes 1⁄2 through 11⁄4) + +* (2) 1200 mm (4 ft) for metric designators 41 through 53 (trade sizes 11⁄2 through 2) + +* (3) 1500 mm (5 ft) for metric designators 63 (trade size 21⁄2) and larger + +> [!important] Exception No. 3: +> Lengths not exceeding 1.8 m (6 ft) from a luminaire terminal connection for tap connections to luminaires as permitted in 410.117(C). + +> [!important] Exception No. 4: +> Lengths not exceeding 1.8 m (6 ft) from the last point where the raceway is securely fastened for connections within an accessible ceiling to a luminaire(s) or other equipment. For the purposes of this exception, listed flexible metal conduit fittings shall be permitted as a means of securement and support. + +#### 348.30(B) Supports. + +Horizontal runs of FMC supported by openings through framing members at intervals not greater than 1.4 m (41⁄2 ft) and securely fastened within 300 mm (12 in.) of termination points shall be permitted. + +### 348.42 Couplings and Connectors. + +Angle connectors shall not be concealed. + +### 348.56 Splices and Taps. + +Splices and taps shall be made in accordance with 300.15. + +### 348.60 Grounding and Bonding. + +If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed. + +Where flexibility is not required after installation, FMC shall be permitted to be used as an equipment grounding conductor when installed in accordance with 250.118(5). + +Where required or installed, equipment grounding conductors shall be installed in accordance with 250.134. + +Where required or installed, equipment bonding jumpers shall be installed in accordance with 250.102. + +# Article 350 Liquidtight Flexible Metal Conduit: Type LFMC + +## Part I. General + +### 350.1 Scope. + +This article covers the use, installation, and construction specifications for liquidtight flexible metal conduit (LFMC) and associated fittings. + +### 350.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Liquidtight Flexible Metal Conduit (LFMC). + +A raceway of circular cross section having an outer liquidtight, nonmetallic, sunlight-resistant jacket over an inner flexible metal core with associated couplings, connectors, and fittings for the installation of electric conductors. + +### 350.6 Listing Requirements. + +LFMC and associated fittings shall be listed. + +## Part II. Installation + +### 350.10 Uses Permitted. + +LFMC shall be permitted to be used in exposed or concealed locations as follows: + +* (1) Where conditions of installation, operation, or maintenance require flexibility or protection from machine oils, liquids, vapors, or solids. + +* (2) In hazardous (classified) locations where specifically permitted by Chapter 5. + +* (3) For direct burial where listed and marked for the purpose. + +* (4) Conductors or cables rated at a temperature higher than the listed temperature rating of LFMC conduit shall be permitted to be installed in LFMC, provided the conductors or cables are not operated at a temperature higher than the listed temperature rating of the LFMC per 110.14(C). + +### 350.12 Uses Not Permitted. + +LFMC shall not be used where subject to physical damage. + +### 350.20 Size. + +#### 350.20(A) Minimum. + +LFMC smaller than metric designator 16 (trade size 1⁄2) shall not be used. + +> [!important] Exception: +> LFMC of metric designator 12 (trade size 3⁄8) shall be permitted as covered in 348.20(A). + +#### 350.20(B) Maximum. + +The maximum size of LFMC shall be metric designator 103 (trade size 4). + +> [!info] Informational Note: +> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions. + +### 350.22 Number of Conductors or Cables. + +#### 350.22(A) Metric Designators 16 through 103 (Trade Sizes 1⁄2 through 4). + +The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. + +Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +#### 350.22(B) Metric Designator 12 (Trade Size 3⁄8). + +The number of conductors shall not exceed that permitted in Table 348.22, “Fittings Outside Conduit” columns. + +### 350.24 Bends — How Made. + +Bends in conduit shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. Bends shall be permitted to be made manually without auxiliary equipment. The radius of the curve to the centerline of any bend shall not be less than required in Table 2, Chapter 9 using the column “Other Bends.” + +### 350.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. + +### 350.28 Trimming. + +All cut ends of conduit shall be trimmed inside and outside to remove rough edges. + +### 350.30 Securing and Supporting. + +LFMC shall be securely fastened in place and supported in accordance with 350.30(A) and (B). + +#### 350.30(A) Securely Fastened. + +LFMC shall be securely fastened in place by an approved means within 300 mm (12 in.) of each box, cabinet, conduit body, or other conduit termination and shall be supported and secured at intervals not to exceed 1.4 m (41⁄2 ft). Where used, cable ties shall be listed and be identified for securement and support. + +> [!important] Exception No. 1: +> Where LFMC is fished between access points through concealed spaces in finished buildings or structures and supporting is impractical. + +> [!important] Exception No. 2: +> Where flexibility is necessary after installation, lengths from the last point where the raceway is securely fastened shall not exceed the following: + +* (1) 900 mm (3 ft) for metric designators 16 through 35 (trade sizes 1⁄2 through 11⁄4) + +* (2) 1200 mm (4 ft) for metric designators 41 through 53 (trade sizes 11⁄2 through 2) + +* (3) 1500 mm (5 ft) for metric designators 63 (trade size 21⁄2) and larger + +> [!important] Exception No. 3: +> Lengths not exceeding 1.8 m (6 ft) from a luminaire terminal connection for tap conductors to luminaires, as permitted in 410.117(C). + +> [!important] Exception No. 4: +> Lengths not exceeding 1.8 m (6 ft) from the last point where the raceway is securely fastened for connections within an accessible ceiling to luminaire(s) or other equipment. + +For the purposes of the exceptions, listed LFMC fittings shall be permitted as a means of securement and support. + +#### 350.30(B) Supports. + +Horizontal runs of LFMC supported by openings through framing members at intervals not greater than 1.4 m (41⁄2 ft) and securely fastened within 300 mm (12 in.) of termination points shall be permitted. + +### 350.42 Couplings and Connectors. + +Only fittings listed for use with LFMC shall be used. Angle connectors shall not be concealed. Straight LFMC fittings shall be permitted for direct burial where marked. + +### 350.56 Splices and Taps. + +Splices and taps shall be made in accordance with 300.15. + +### 350.60 Grounding and Bonding. + +If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed. + +Where flexibility is not required after installation, LFMC shall be permitted to be used as an equipment grounding conductor when installed in accordance with 250.118(6). + +Where required or installed, equipment grounding conductors shall be installed in accordance with 250.134. + +Where required or installed, equipment bonding jumpers shall be installed in accordance with 250.102. + +> [!info] Informational Note: +> See 501.30(B), 502.30(B), 503.30(B), 505.25(B), and 506.25(B) for types of equipment grounding conductors. + +## Part III. Construction Specifications + +### 350.120 Marking. + +LFMC shall be marked according to 110.21. The trade size and other information required by the listing shall also be marked on the conduit. Conduit suitable for direct burial shall be so marked. + +# Article 352 Rigid Polyvinyl Chloride Conduit: Type PVC + +## Part I. General + +### 352.1 Scope. + +This article covers the use, installation, and construction specifications for rigid polyvinyl chloride conduit (PVC) and associated fittings. + +> [!info] Informational Note: +> Refer to Article 353 for High Density Polyethylene Conduit: Type HDPE, and Article 355 for Reinforced + +Thermosetting Resin Conduit: Type RTRC. + +### 352.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Rigid Polyvinyl Chloride Conduit (PVC). + +A rigid nonmetallic raceway of circular cross section, with integral or associated couplings, connectors, and fittings for the installation of electrical conductors and cables. + +### 352.6 Listing Requirements. + +PVC conduit, factory elbows, and associated fittings shall be listed. + +## Part II. Installation + +### 352.10 Uses Permitted. + +The use of PVC conduit shall be permitted in accordance with 352.10(A) through (I). + +> [!info] Informational Note: +> Extreme cold may cause some nonmetallic conduits to become brittle and, therefore, more susceptible to damage from physical contact. + +#### 352.10(A) Concealed. + +PVC conduit shall be permitted in walls, floors, and ceilings. + +#### 352.10(B) Corrosive Influences. + +PVC conduit shall be permitted in locations subject to severe corrosive influences as covered in 300.6 and where subject to chemicals for which the materials are specifically approved. + +#### 352.10(C) Cinders. + +PVC conduit shall be permitted in cinder fill. + +#### 352.10(D) Wet Locations. + +PVC conduit shall be permitted in portions of dairies, laundries, canneries, or other wet locations, and in locations where walls are frequently washed, the entire conduit system, including boxes and fittings used therewith, shall be installed and equipped so as to prevent water from entering the conduit. All supports, bolts, straps, screws, and so forth, shall be of corrosion-resistant materials or be protected against corrosion by approved corrosion-resistant materials. + +#### 352.10(E) Dry and Damp Locations. + +PVC conduit shall be permitted for use in dry and damp locations not prohibited by 352.12. + +#### 352.10(F) Exposed. + +PVC conduit shall be permitted for exposed work. PVC conduit used exposed in areas of physical damage shall be identified for the use. + +> [!info] Informational Note: +> PVC Conduit, Type Schedule 80, is identified for areas of physical damage. + +#### 352.10(G) Underground Installations. + +For underground installations, PVC shall be permitted for direct burial and underground encased in concrete. See 300.5 and 300.50. + +#### 352.10(H) Support of Conduit Bodies. + +PVC conduit shall be permitted to support nonmetallic conduit bodies not larger than the largest trade size of an entering raceway. + +These conduit bodies shall not support luminaires or other equipment and shall not contain devices other than splicing devices as permitted by 110.14(B) and 314.16(C)(2). + +#### 352.10(I) Insulation Temperature Limitations. + +Conductors or cables rated at a temperature higher than the listed temperature rating of PVC conduit shall be permitted to be installed in PVC conduit, provided the conductors or cables are not operated at a temperature higher than the listed temperature rating of the + +PVC conduit. + +### 352.12 Uses Not Permitted. + +PVC conduit shall not be used under the conditions specified in 352.12(A) through (E). + +#### 352.12(A) Hazardous (Classified) Locations. + +In any hazardous (classified) location, except as permitted by other articles of this Code. + +#### 352.12(B) Support of Luminaires. + +For the support of luminaires or other equipment not described in 352.10(H). + +#### 352.12(C) Physical Damage. + +Where subject to physical damage unless identified for such use. + +#### 352.12(D) Ambient Temperatures. + +Where subject to ambient temperatures in excess of 50°C (122°F) unless listed otherwise. + +#### 352.12(E) Theaters and Similar Locations. + +In theaters and similar locations, except as provided in 518.4 and 520.5. + +### 352.20 Size. + +#### 352.20(A) Minimum. + +PVC conduit smaller than metric designator 16 (trade size 1⁄2) shall not be used. + +#### 352.20(B) Maximum. + +PVC conduit larger than metric designator 155 (trade size 6) shall not be used. + +> [!info] Informational Note: +> The trade sizes and metric designators are for identification purposes only and do not relate to actual dimensions. + +See 300.1(C). + +### 352.22 Number of Conductors. + +The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. + +Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +### 352.24 Bends — How Made. + +Bends shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. + +Field bends shall be made only with identified bending equipment. The radius of the curve to the centerline of such bends shall not be less than shown in Table 2, Chapter 9. + +### 352.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. + +### 352.28 Trimming. + +All cut ends shall be trimmed inside and outside to remove rough edges. + +### 352.30 Securing and Supporting. + +PVC conduit shall be installed as a complete system as provided in 300.18 and shall be fastened so that movement from thermal expansion or contraction is permitted. PVC conduit shall be securely fastened and supported in accordance with 352.30(A) and (B). + +#### 352.30(A) Securely Fastened. + +PVC conduit shall be securely fastened within 900 mm (3 ft) of each outlet box, junction box, device box, conduit body, or other conduit termination. Conduit listed for securing at other than 900 mm (3 ft) shall be permitted to be installed in accordance with the listing. + +#### 352.30(B) Supports. + +PVC conduit shall be supported as required in Table 352.30. Conduit listed for support at spacings other than as shown in Table 352.30 shall be permitted to be installed in accordance with the listing. Horizontal runs of PVC conduit supported by openings through framing members at intervals not exceeding those in Table 352.30 and securely fastened within 900 mm (3 ft) of termination points shall be permitted. + +Table 352.30 Support of Rigid Polyvinyl Chloride Conduit (PVC) + +Conduit Size Maximum Spacing Between Supports + +Metric Designator Trade Size mm or m ft +16–27 1⁄2–1 900 mm 3 +35–53 11⁄4–2 1.5 m 5 +63–78 21⁄2–3 1.8 m 6 +91–129 31⁄2–5 2.1 m 7 + +Conduit Size Maximum Spacing Between Supports + +Metric Designator Trade Size mm or m ft +155 6 2.5 m 8 + +### 352.44 Expansion Fittings. + +Expansion fittings for PVC conduit shall be provided to compensate for thermal expansion and contraction where the length change, in accordance with Table 352.44, is expected to be 6 mm (1⁄4 in.) or greater in a straight run between securely mounted items such as boxes, cabinets, elbows, or other conduit terminations. + +Table 352.44 Expansion Characteristics of PVC Rigid Nonmetallic Conduit Coefficient of Thermal + +Expansion = 6.084 × 10 mm/mm/°C (3.38 × 10 in./in./°F) + +Temperature + +Change (°C) + +Length Change of + +PVC Conduit +(mm/m) + +Temperature + +Change (°F) + +Length Change of + +PVC Conduit +(in./100 ft) + +Temperature + +Change (°F) + +Length Change of + +PVC Conduit +(in./100 ft) +5 0.30 5 0.20 105 4.26 +10 0.61 10 0.41 110 4.46 +15 0.91 15 0.61 115 4.66 +20 1.22 20 0.81 120 4.87 +25 1.52 25 1.01 125 5.07 +30 1.83 30 1.22 130 5.27 +35 2.13 35 1.42 135 5.48 +40 2.43 40 1.62 140 5.68 +45 2.74 45 1.83 145 5.88 +50 3.04 50 2.03 150 6.08 +55 3.35 55 2.23 155 6.29 +60 3.65 60 2.43 160 6.49 +65 3.95 65 2.64 165 6.69 +70 4.26 70 2.84 170 6.90 +75 4.56 75 3.04 175 7.10 +80 4.87 80 3.24 180 7.30 +85 5.17 85 3.45 185 7.50 +90 5.48 90 3.65 190 7.71 +95 5.78 95 3.85 195 7.91 +100 6.08 100 4.06 200 8.11 + +### 352.46 Bushings. + +Where a conduit enters a box, fitting, or other enclosure, a bushing or adapter shall be provided to protect the wire from abrasion unless the box, fitting, or enclosure design provides equivalent protection. + +> [!info] Informational Note: +> See 300.4(G) for the protection of conductors 4 AWG and larger at bushings. + +### 352.48 Joints. + +All joints between lengths of conduit, and between conduit and couplings, fittings, and boxes, shall be made by an approved method. + +### 352.56 Splices and Taps. + +Splices and taps shall be made in accordance with 300.15. + +### 352.60 Grounding. + +Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the conduit. +–5 –5 + +> [!important] Exception No. 1: +> As permitted in 250.134, Exception No. 2, for dc circuits and 250.134, Exception No. 1, for separately run equipment grounding conductors. + +> [!important] Exception No. 2: +> Where the grounded conductor is used to ground equipment as permitted in 250.142. + +## Part III. Construction Specifications + +### 352.100 Construction. + +PVC conduit shall be made of rigid (nonplasticized) polyvinyl chloride (PVC). PVC conduit and fittings shall be composed of suitable nonmetallic material that is resistant to moisture and chemical atmospheres. For use aboveground, it shall also be flame retardant, resistant to impact and crushing, resistant to distortion from heat under conditions likely to be encountered in service, and resistant to low temperature and sunlight effects. For use underground, the material shall be acceptably resistant to moisture and corrosive agents and shall be of sufficient strength to withstand abuse, such as by impact and crushing, in handling and during installation. Where intended for direct burial, without encasement in concrete, the material shall also be capable of withstanding continued loading that is likely to be encountered after installation. + +### 352.120 Marking. + +Each length of PVC conduit shall be clearly and durably marked at least every 3 m (10 ft) as required in the first sentence of 110.21(A). + +The type of material shall also be included in the marking unless it is visually identifiable. For conduit recognized for use aboveground, these markings shall be permanent. For conduit limited to underground use only, these markings shall be sufficiently durable to remain legible until the material is installed. Conduit shall be permitted to be surface marked to indicate special characteristics of the material. + +> [!info] Informational Note: +> Examples of these markings include but are not limited to “limited smoke” and “sunlight resistant.” + +# Article 353 High Density Polyethylene Conduit: Type HDPE Conduit + +## Part I. General + +### 353.1 Scope. + +This article covers the use, installation, and construction specifications for high density polyethylene (HDPE) conduit and associated fittings. + +> [!info] Informational Note: +> Refer to Article 352 for Rigid Polyvinyl Chloride Conduit: Type PVC and Article 355 for Reinforced Thermosetting + +Resin Conduit: Type RTRC. + +### 353.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +High Density Polyethylene (HDPE) Conduit. + +A nonmetallic raceway of circular cross section, with associated couplings, connectors, and fittings for the installation of electrical conductors. + +### 353.6 Listing Requirements. + +HDPE conduit and associated fittings shall be listed. + +## Part II. Installation + +### 353.10 Uses Permitted. + +The use of HDPE conduit shall be permitted under the following conditions: + +* (1) In discrete lengths or in continuous lengths from a reel + +* (2) In locations subject to severe corrosive influences as covered in 300.6 and where subject to chemicals for which the conduit is listed + +* (3) In cinder fill + +* (4) In direct burial installations in earth or concrete + +Informational Note to (4): Refer to 300.5 and 300.50 for underground installations. + +* (5) Above ground, except as prohibited in 353.12, where encased in not less than 50 mm (2 in.) of concrete. + +* (6) Conductors or cables rated at a temperature higher than the listed temperature rating of HDPE conduit shall be permitted to be installed in HDPE conduit, provided the conductors or cables are not operated at a temperature higher than the listed temperature rating of the HDPE conduit. + +### 353.12 Uses Not Permitted. + +HDPE conduit shall not be used under the following conditions: + +* (1) Where exposed + +* (2) Within a building + +* (3) In any hazardous (classified) location, except as permitted by other articles in this Code + +* (4) Where subject to ambient temperatures in excess of 50°C (122°F) unless listed otherwise + +### 353.20 Size. + +#### 353.20(A) Minimum. + +HDPE conduit smaller than metric designator 16 (trade size 1⁄2) shall not be used. + +#### 353.20(B) Maximum. + +HDPE conduit larger than metric designator 155 (trade size 6) shall not be used. + +> [!info] Informational Note: +> The trade sizes and metric designators are for identification purposes only and do not relate to actual dimensions. + +See 300.1(C). + +### 353.22 Number of Conductors. + +The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. + +Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +### 353.24 Bends — How Made. + +Bends shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. + +Bends shall be permitted to be made manually without auxiliary equipment, and the radius of the curve to the centerline of such bends shall not be less than shown in Table 354.24. For conduits of metric designators 129 and 155 (trade sizes 5 and 6) the allowable radii of bends shall be in accordance with specifications provided by the manufacturer. + +### 353.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. + +### 353.28 Trimming. + +All cut ends shall be trimmed inside and outside to remove rough edges. + +### 353.46 Bushings. + +Where a conduit enters a box, fitting, or other enclosure, a bushing or adapter shall be provided to protect the wire from abrasion unless the box, fitting, or enclosure design provides equivalent protection. + +> [!info] Informational Note: +> See 300.4(G) for the protection of conductors 4 AWG and larger at bushings. + +### 353.48 Joints. + +All joints between lengths of conduit, and between conduit and couplings, fittings, and boxes, shall be made by an approved method. + +> [!info] Informational Note: +> HDPE conduit can be joined using either heat fusion, electrofusion, or mechanical fittings. + +### 353.56 Splices and Taps. + +Splices and taps shall be made in accordance with 300.15. + +### 353.60 Grounding. + +Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the conduit. + +> [!important] Exception No. 1: +> The equipment grounding conductor shall be permitted to be run separately from the conduit where used for grounding dc circuits as permitted in 250.134, Exception No. 2. + +> [!important] Exception No. 2: +> The equipment grounding conductor shall not be required where the grounded conductor is used to ground equipment as permitted in 250.142. + +## Part III. Construction Specifications + +### 353.100 Construction. + +HDPE conduit shall be composed of high density polyethylene that is resistant to moisture and chemical atmospheres. The material shall be resistant to moisture and corrosive agents and shall be of sufficient strength to withstand abuse, such as by impact and crushing, in handling and during installation. Where intended for direct burial, without encasement in concrete, the material shall also be capable of withstanding continued loading that is likely to be encountered after installation. + +### 353.120 Marking. + +Each length of HDPE shall be clearly and durably marked at least every 3 m (10 ft) as required in 110.21. The type of material shall also be included in the marking. + +# Article 354 Nonmetallic Underground Conduit with Conductors: Type NUCC + +## Part I. General + +### 354.1 Scope. + +This article covers the use, installation, and construction specifications for nonmetallic underground conduit with conductors (NUCC). + +### 354.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Nonmetallic Underground Conduit with Conductors (NUCC). + +A factory assembly of conductors or cables inside a nonmetallic, smooth wall raceway with a circular cross section. + +### 354.6 Listing Requirements. + +NUCC and associated fittings shall be listed. + +## Part II. Installation + +### 354.10 Uses Permitted. + +The use of NUCC and fittings shall be permitted in the following: + +* (1) For direct burial underground installation (For minimum cover requirements, see Table 300.5 and Table 300.50 under Rigid + +Nonmetallic Conduit.) + +* (2) Encased or embedded in concrete + +* (3) In cinder fill + +* (4) In underground locations subject to severe corrosive influences as covered in 300.6 and where subject to chemicals for which the assembly is specifically approved + +* (5) Aboveground, except as prohibited in 354.12, where encased in not less than 50 mm (2 in.) of concrete + +### 354.12 Uses Not Permitted. + +NUCC shall not be used in the following: + +* (1) In exposed locations + +* (2) Inside buildings + +> [!important] Exception: +> The conductor or the cable portion of the assembly, where suitable, shall be permitted to extend within the building for termination purposes in accordance with 300.3. + +* (3) In any hazardous (classified) location, except as permitted by other articles of this Code + +### 354.20 Size. + +#### 354.20(A) Minimum. + +NUCC smaller than metric designator 16 (trade size 1⁄2) shall not be used. + +#### 354.20(B) Maximum. + +NUCC larger than metric designator 103 (trade size 4) shall not be used. + +> [!info] Informational Note: +> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions. + +### 354.22 Number of Conductors. + +The number of conductors or cables shall not exceed that permitted by the percentage fill in Table 1, Chapter 9. + +### 354.24 Bends — How Made. + +Bends shall be manually made so that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. The radius of the curve of the centerline of such bends shall not be less than shown in Table 354.24. + +Table 354.24 Minimum Bending Radius for Nonmetallic + +Underground Conduit with Conductors (NUCC) + +Conduit Size Minimum Bending Radius + +Metric Designator Trade Size mm in. +16 1⁄2 250 10 +21 3⁄4 300 12 +27 1 350 14 +35 11⁄4 450 18 +41 11⁄2 500 20 +53 2 650 26 +63 21⁄2 900 36 +78 3 1200 48 +103 4 1500 60 + +### 354.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between termination points. + +### 354.28 Trimming. + +For termination, the conduit shall be trimmed away from the conductors or cables using an approved method that will not damage the conductor or cable insulation or jacket. All conduit ends shall be trimmed inside and out to remove rough edges. + +### 354.46 Bushings. + +Where the NUCC enters a box, fitting, or other enclosure, a bushing or adapter shall be provided to protect the conductor or cable from abrasion unless the design of the box, fitting, or enclosure provides equivalent protection. + +> [!info] Informational Note: +> See 300.4(G) for the protection of conductors size 4 AWG or larger. + +### 354.48 Joints. + +All joints between conduit, fittings, and boxes shall be made by an approved method. + +### 354.50 Conductor Terminations. + +All terminations between the conductors or cables and equipment shall be made by an approved method for that type of conductor or cable. + +### 354.56 Splices and Taps. + +Splices and taps shall be made in junction boxes or other enclosures. + +### 354.60 Grounding. + +Where equipment grounding is required, an assembly containing a separate equipment grounding conductor shall be used. + +## Part III. Construction Specifications + +### 354.100 Construction. + +#### 354.100(A) General. + +NUCC is an assembly that is provided in continuous lengths shipped in a coil, reel, or carton. + +#### 354.100(B) Nonmetallic Underground Conduit. + +The nonmetallic underground conduit shall be listed and composed of a material that is resistant to moisture and corrosive agents. It shall also be capable of being supplied on reels without damage or distortion and shall be of sufficient strength to withstand abuse, such as impact or crushing, in handling and during installation without damage to conduit or conductors. + +#### 354.100(C) Conductors and Cables. + +Conductors and cables used in NUCC shall be listed and shall comply with 310.10(C). Conductors of different systems shall be installed in accordance with 300.3(C). + +#### 354.100(D) Conductor Fill. + +The maximum number of conductors or cables in NUCC shall not exceed that permitted by the percentage fill in Table 1, Chapter 9. + +### 354.120 Marking. + +NUCC shall be clearly and durably marked at least every 3.05 m (10 ft) as required by 110.21. The type of conduit material shall also be included in the marking. + +Identification of conductors or cables used in the assembly shall be provided on a tag attached to each end of the assembly or to the side of a reel. Enclosed conductors or cables shall be marked in accordance with 310.8. + +# Article 355 Reinforced Thermosetting Resin Conduit: Type RTRC + +## Part I. General + +### 355.1 Scope. + +This article covers the use, installation, and construction specification for reinforced thermosetting resin conduit (RTRC) and associated fittings. + +> [!info] Informational Note: +> Refer to Article 352 for Rigid Polyvinyl Chloride Conduit: Type PVC, and Article 353 for High Density Polyethylene + +Conduit: Type HDPE. + +### 355.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Reinforced Thermosetting Resin Conduit (RTRC). + +A rigid nonmetallic raceway of circular cross section, with integral or associated couplings, connectors, and fittings for the installation of electrical conductors and cables. + +### 355.6 Listing Requirements. + +RTRC, factory elbows, and associated fittings shall be listed. + +## Part II. Installation + +### 355.10 Uses Permitted. + +The use of RTRC shall be permitted in accordance with 355.10(A) through (I). + +#### 355.10(A) Concealed. + +RTRC shall be permitted in walls, floors, and ceilings. + +#### 355.10(B) Corrosive Influences. + +RTRC shall be permitted in locations subject to severe corrosive influences as covered in 300.6 and where subject to chemicals for which the materials are specifically approved. + +#### 355.10(C) Cinders. + +RTRC shall be permitted in cinder fill. + +#### 355.10(D) Wet Locations. + +RTRC shall be permitted in portions of dairies, laundries, canneries, or other wet locations, and in locations where walls are frequently washed, the entire conduit system, including boxes and fittings used therewith, shall be installed and equipped so as to prevent water from entering the conduit. All supports, bolts, straps, screws, and so forth, shall be of corrosion-resistant materials or be protected against corrosion by approved corrosion-resistant materials. + +#### 355.10(E) Dry and Damp Locations. + +RTRC shall be permitted for use in dry and damp locations not prohibited by 355.12. + +#### 355.10(F) Exposed. + +RTRC shall be permitted for exposed work if identified for such use. + +> [!info] Informational Note: +> RTRC, Type XW, is identified for areas of physical damage. + +#### 355.10(G) Underground Installations. + +For underground installations, see 300.5 and 300.50. + +#### 355.10(H) Support of Conduit Bodies. + +RTRC shall be permitted to support nonmetallic conduit bodies not larger than the largest trade size of an entering raceway. These conduit bodies shall not support luminaires or other equipment and shall not contain devices other than splicing devices as permitted by +110.14(B) and 314.16(C)(2). + +#### 355.10(I) Insulation Temperature Limitations. + +Conductors or cables rated at a temperature higher than the listed temperature rating of RTRC conduit shall be permitted to be installed in RTRC conduit, if the conductors or cables are not operated at a temperature higher than the listed temperature rating of the RTRC conduit. + +### 355.12 Uses Not Permitted. + +RTRC shall not be used under the following conditions. + +#### 355.12(A) Hazardous (Classified) Locations. + +* (1) In any hazardous (classified) location, except as permitted by other articles in this Code + +* (2) In Class I, Division 2 locations, except as permitted in 501.10(B)(1)(6) + +#### 355.12(B) Support of Luminaires. + +For the support of luminaires or other equipment not described in 355.10(H). + +#### 355.12(C) Physical Damage. + +Where subject to physical damage unless identified for such use. + +#### 355.12(D) Ambient Temperatures. + +Where subject to ambient temperatures in excess of 50°C (122°F) unless listed otherwise. + +#### 355.12(E) Theaters and Similar Locations. + +In theaters and similar locations, except as provided in 518.4 and 520.5. + +### 355.20 Size. + +#### 355.20(A) Minimum. + +RTRC smaller than metric designator 16 (trade size 1⁄2) shall not be used. + +#### 355.20(B) Maximum. + +RTRC larger than metric designator 155 (trade size 6) shall not be used. + +> [!info] Informational Note: +> The trade sizes and metric designators are for identification purposes only and do not relate to actual dimensions. + +See 300.1(C). + +### 355.22 Number of Conductors. + +The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +### 355.24 Bends — How Made. + +Bends shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. + +Field bends shall be made only with identified bending equipment. The radius of the curve to the centerline of such bends shall not be less than shown in Table 2, Chapter 9. + +### 355.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. + +### 355.28 Trimming. + +All cut ends shall be trimmed inside and outside to remove rough edges. + +### 355.30 Securing and Supporting. + +RTRC shall be installed as a complete system in accordance with 300.18 and shall be securely fastened in place and supported in accordance with 355.30(A) and (B). + +#### 355.30(A) Securely Fastened. + +RTRC shall be securely fastened within 900 mm (3 ft) of each outlet box, junction box, device box, conduit body, or other conduit termination. Conduit listed for securing at other than 900 mm (3 ft) shall be permitted to be installed in accordance with the listing. + +#### 355.30(B) Supports. + +RTRC shall be supported as required in Table 355.30. Conduit listed for support at spacing other than as shown in Table 355.30 shall be permitted to be installed in accordance with the listing. Horizontal runs of RTRC supported by openings through framing members at intervals not exceeding those in Table 355.30 and securely fastened within 900 mm (3 ft) of termination points shall be permitted. + +Table 355.30 Support of Reinforced Thermosetting Resin Conduit +(RTRC) + +Conduit Size Maximum Spacing Between Supports + +Metric Designator Trade Size mm or m ft +16–27 1⁄2–1 900 mm 3 +35–53 11⁄4–2 1.5 m 5 +63–78 21⁄2–3 1.8 m 6 +91–129 31⁄2–5 2.1 m 7 +155 6 2.5 m 8 + +### 355.44 Expansion Fittings. + +Expansion fittings for RTRC shall be provided to compensate for thermal expansion and contraction where the length change, in accordance with Table 355.44, is expected to be 6 mm (1⁄4 in.) or greater in a straight run between securely mounted items such as boxes, cabinets, elbows, or other conduit terminations. + +Table 355.44 Expansion Characteristics of Reinforced Thermosetting Resin Conduit (RTRC) Coefficient of Thermal Expansion = 2.7 × 10 mm/mm/°C (1.5 × 10 in./in./°F) + +Temperature + +Change (°C) + +Length Change of + +RTRC Conduit +(mm/m) + +Temperature + +Change (°F) + +Length Change of + +RTRC Conduit +(in./100 ft) + +Temperature + +Change (°F) + +Length Change of RTRC + +Conduit +(in./100 ft) +5 0.14 5 0.09 105 1.89 +10 0.27 10 0.18 110 1.98 +15 0.41 15 0.27 115 2.07 +20 0.54 20 0.36 120 2.16 +25 0.68 25 0.45 125 2.25 +30 0.81 30 0.54 130 2.34 +35 0.95 35 0.63 135 2.43 +40 1.08 40 0.72 140 2.52 +45 1.22 45 0.81 145 2.61 +–5 –5 + +Temperature + +Change (°C) + +Length Change of + +RTRC Conduit +(mm/m) + +Temperature + +Change (°F) + +Length Change of + +RTRC Conduit +(in./100 ft) + +Temperature + +Change (°F) + +Length Change of RTRC + +Conduit +(in./100 ft) +50 1.35 50 0.90 150 2.70 +55 1.49 55 0.99 155 2.79 +60 1.62 60 1.08 160 2.88 +65 1.76 65 1.17 165 2.97 +70 1.89 70 1.26 170 3.06 +75 2.03 75 1.35 175 3.15 +80 2.16 80 1.44 180 3.24 +85 2.30 85 1.53 185 3.33 +90 2.43 90 1.62 190 3.42 +95 2.57 95 1.71 195 3.51 +100 2.70 100 1.80 200 3.60 + +### 355.46 Bushings. + +Where a conduit enters a box, fitting, or other enclosure, a bushing or adapter shall be provided to protect the wire from abrasion unless the box, fitting, or enclosure design provides equivalent protection. + +> [!info] Informational Note: +> See 300.4(G) for the protection of conductors 4 AWG and larger at bushings. + +### 355.48 Joints. + +All joints between lengths of conduit, and between conduit and couplings, fitting, and boxes, shall be made by an approved method. + +### 355.56 Splices and Taps. + +Splices and taps shall be made in accordance with 300.15. + +### 355.60 Grounding. + +Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the conduit. + +> [!important] Exception No. 1: +> As permitted in 250.134, Exception No. 2, for dc circuits and 250.134, Exception No. 1, for separately run equipment grounding conductors. + +> [!important] Exception No. 2: +> Where the grounded conductor is used to ground equipment as permitted in 250.142. + +## Part III. Construction Specifications + +### 355.100 Construction. + +RTRC and fittings shall be composed of suitable nonmetallic material that is resistant to moisture and chemical atmospheres. For use aboveground, it shall also be flame retardant, resistant to impact and crushing, resistant to distortion from heat under conditions likely to be encountered in service, and resistant to low temperature and sunlight effects. For use underground, the material shall be acceptably resistant to moisture and corrosive agents and shall be of sufficient strength to withstand abuse, such as by impact and crushing, in handling and during installation. Where intended for direct burial, without encasement in concrete, the material shall also be capable of withstanding continued loading that is likely to be encountered after installation. + +### 355.120 Marking. + +Each length of RTRC shall be clearly and durably marked at least every 3 m (10 ft) as required in the first sentence of 110.21(A). The type of material shall also be included in the marking unless it is visually identifiable. For conduit recognized for use aboveground, these markings shall be permanent. For conduit limited to underground use only, these markings shall be sufficiently durable to remain legible until the material is installed. Conduit shall be permitted to be surface marked to indicate special characteristics of the material. + +> [!info] Informational Note: +> Examples of these markings include but are not limited to “limited smoke” and “sunlight resistant.” + +# Article 356 Liquidtight Flexible Nonmetallic Conduit: Type LFNC + +## Part I. General + +### 356.1 Scope. + +This article covers the use, installation, and construction specifications for liquidtight flexible nonmetallic conduit (LFNC) and associated fittings. + +### 356.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Liquidtight Flexible Nonmetallic Conduit (LFNC). + +A raceway of circular cross section of various types as follows: + +* (1) A smooth seamless inner core and cover bonded together and having one or more reinforcement layers between the core and covers, designated as Type LFNC-A + +* (2) A smooth inner surface with integral reinforcement within the raceway wall, designated as Type LFNC-B + +* (3) A corrugated internal and external surface without integral reinforcement within the raceway wall, designated as Type LFNC-C + +> [!info] Informational Note: +> FNMC is an alternative designation for LFNC. + +### 356.6 Listing Requirements. + +LFNC and associated fittings shall be listed. + +## Part II. Installation + +### 356.10 Uses Permitted. + +LFNC shall be permitted to be used in exposed or concealed locations for the following purposes: + +* (1) Where flexibility is required for installation, operation, or maintenance. + +* (2) Where protection of the contained conductors is required from vapors, machine oils, liquids, or solids. + +* (3) For outdoor locations where listed and marked as suitable for the purpose. + +* (4) For direct burial where listed and marked for the purpose. + +* (5) Type LFNC shall be permitted to be installed in lengths longer than 1.8 m (6 ft) where secured in accordance with 356.30. + +* (6) Type LFNC-B as a listed manufactured prewired assembly, metric designator 16 through 27 (trade size 1⁄2 through 1) conduit. + +* (7) For encasement in concrete where listed for direct burial and installed in compliance with 356.42. + +* (8) Conductors or cables rated at a temperature rating of LFNC conduit shall be permitted to be installed in LFNC, provided the conductors or cables are not operated at a temperature higher than the listed temperature rating of the LFNC. + +> [!info] Informational Note: +> Extreme cold can cause some types of nonmetallic conduits to become brittle and therefore more susceptible to damage from physical contact. + +### 356.12 Uses Not Permitted. + +LFNC shall not be used as follows: + +* (1) Where subject to physical damage + +* (2) Where any combination of ambient and conductor temperatures is in excess of that for which it is listed + +* (3) In lengths longer than 1.8 m (6 ft), except as permitted by 356.10(5) or where a longer length is approved as essential for a required degree of flexibility + +* (4) In any hazardous (classified) location, except as permitted by other articles in this Code + +### 356.20 Size. + +#### 356.20(A) Minimum. + +LFNC smaller than metric designator 16 (trade size 1⁄2) shall not be used unless permitted in 356.20(A)(1) or (A)(2) for metric designator 12 (trade size 3⁄8). + +* (1) For enclosing the leads of motors as permitted in 430.245(B) + +* (2) In lengths not exceeding 1.8 m (6 ft) as part of a listed assembly for tap connections to luminaires as required in 410.117(C), or for utilization equipment + +#### 356.20(B) Maximum. + +LFNC larger than metric designator 103 (trade size 4) shall not be used. + +> [!info] Informational Note: +> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions. + +### 356.22 Number of Conductors. + +The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. + +Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +### 356.24 Bends — How Made. + +Bends in conduit shall be so made that the conduit is not damaged and the internal diameter of the conduit is not effectively reduced. + +Bends shall be permitted to be made manually without auxiliary equipment. The radius of the curve to the centerline of any bend shall not be less than shown in Table 2, Chapter 9 using the column “Other Bends.” + +### 356.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. + +### 356.28 Trimming. + +All cut ends of conduit shall be trimmed inside and outside to remove rough edges. + +### 356.30 Securing and Supporting. + +Type LFNC shall be securely fastened and supported in accordance with one of the following: + +* (1) Where installed in lengths exceeding 1.8 m (6 ft), the conduit shall be securely fastened at intervals not exceeding 900 mm (3 ft) and within 300 mm (12 in.) on each side of every outlet box, junction box, cabinet, or fitting. Where used, cable ties shall be listed for the application and for securing and supporting. + +* (2) Securing or supporting of the conduit shall not be required where it is fished, installed in lengths not exceeding 900 mm (3 ft) at terminals where flexibility is required, or installed in lengths not exceeding 1.8 m (6 ft) from a luminaire terminal connection for tap conductors to luminaires permitted in 410.117(C). + +* (3) Horizontal runs of LFNC supported by openings through framing members at intervals not exceeding 900 mm (3 ft) and securely fastened within 300 mm (12 in.) of termination points shall be permitted. + +* (4) Securing or supporting of LFNC shall not be required where installed in lengths not exceeding 1.8 m (6 ft) from the last point where the raceway is securely fastened for connections within an accessible ceiling to a luminaire(s) or other equipment. For the purpose of 356.30, listed liquidtight flexible nonmetallic conduit fittings shall be permitted as a means of support. + +### 356.42 Couplings and Connectors. + +Only fittings listed for use with LFNC shall be used. Angle connectors shall not be used for concealed raceway installations. Straight + +LFNC fittings are permitted for direct burial or encasement in concrete. + +### 356.56 Splices and Taps. + +Splices and taps shall be made in accordance with 300.15. + +### 356.60 Grounding. + +Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the conduit. + +> [!important] Exception No. 1: +> As permitted in 250.134, Exception No. 2, for dc circuits and 250.134, Exception No. 1, for separately run equipment grounding conductors. + +> [!important] Exception No. 2: +> Where the grounded conductor is used to ground equipment as permitted in 250.142. + +## Part III. Construction Specifications + +### 356.100 Construction. + +LFNC-B as a prewired manufactured assembly shall be provided in continuous lengths capable of being shipped in a coil, reel, or carton without damage. + +### 356.120 Marking. + +LFNC shall be marked at least every 600 mm (2 ft) in accordance with 110.21. The marking shall include a type designation in accordance with 356.2 and the trade size. Conduit that is intended for outdoor use or direct burial shall be marked. + +The type, size, and quantity of conductors used in prewired manufactured assemblies shall be identified by means of a printed tag or label attached to each end of the manufactured assembly and either the carton, coil, or reel. The enclosed conductors shall be marked in accordance with 310.8. + +# Article 358 Electrical Metallic Tubing: Type EMT + +## Part I. General + +### 358.1 Scope. + +This article covers the use, installation, and construction specifications for electrical metallic tubing (EMT) and associated fittings. + +### 358.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Electrical Metallic Tubing (EMT). + +An unthreaded thinwall raceway of circular cross section designed for the physical protection and routing of conductors and cables and for use as an equipment grounding conductor when installed utilizing appropriate fittings. + +### 358.6 Listing Requirements. + +EMT, factory elbows, and associated fittings shall be listed. + +## Part II. Installation + +### 358.10 Uses Permitted. + +#### 358.10(A) Exposed and Concealed. + +The use of EMT shall be permitted for both exposed and concealed work for the following: + +* (1) In concrete, in direct contact with the earth or in areas subject to severe corrosive influences where installed in accordance with +358.10(B) + +* (2) In dry, damp, and wet locations + +* (3) In any hazardous (classified) location as permitted by other articles in this Code + +#### 358.10(B) Corrosive Environments. + +##### 358.10(B)(1) Galvanized Steel and Stainless Steel EMT, Elbows, and Fittings. + +Galvanized steel and stainless steel EMT, elbows, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and approved as suitable for the condition. + +##### 358.10(B)(2) Supplementary Protection of Aluminum EMT. + +Aluminum EMT shall be provided with approved supplementary corrosion protection where encased in concrete or in direct contact with the earth. + +#### 358.10(C) Cinder Fill. + +Galvanized steel and stainless steel EMT shall be permitted to be installed in cinder concrete or cinder fill where subject to permanent moisture when protected on all sides by a layer of noncinder concrete at least 50 mm (2 in.) thick or when the tubing is installed at least +450 mm (18 in.) under the fill. + +#### 358.10(D) Wet Locations. + +All supports, bolts, straps, screws, and so forth shall be of corrosion-resistant materials or protected against corrosion by corrosionresistant materials. + +> [!info] Informational Note: +> See 300.6 for protection against corrosion. + +#### 358.10(E) Physical Damage. + +Steel and stainless steel EMT shall be permitted to be installed where subject to physical damage. + +### 358.12 Uses Not Permitted. + +EMT shall not be used under the following conditions: + +* (1) Where subject to severe physical damage + +* (2) For the support of luminaires or other equipment except conduit bodies no larger than the largest trade size of the tubing + +### 358.14 Dissimilar Metals. + +Where practicable, dissimilar metals in contact anywhere in the system shall be avoided to eliminate the possibility of galvanic action. + +Stainless steel and aluminum fittings and enclosures shall be permitted to be used with galvanized steel EMT, and galvanized steel fittings and enclosures shall be permitted to be used with aluminum EMT where not subject to severe corrosive influences. + +Stainless steel EMT shall only be used with the following: + +* (1) Stainless steel fittings + +* (2) Stainless steel boxes and enclosures + +* (3) Steel (galvanized, painted, powder or PVC coated, and so forth) boxes and enclosures when not subject to severe corrosive influences + +* (4) Stainless steel, nonmetallic, or approved accessories + +### 358.20 Size. + +#### 358.20(A) Minimum. + +EMT smaller than metric designator 16 (trade size 1⁄2) shall not be used. + +> [!important] Exception: +> For enclosing the leads of motors as permitted in 430.245(B). + +#### 358.20(B) Maximum. + +The maximum size of EMT shall be metric designator 103 (trade size 4). + +> [!info] Informational Note: +> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions. + +### 358.22 Number of Conductors. + +The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. + +Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +### 358.24 Bends — How Made. + +Bends shall be made so that the tubing is not damaged and the internal diameter of the tubing is not effectively reduced. The radius of the curve of any field bend to the centerline of the tubing shall not be less than shown in Table 2, Chapter 9 for one-shot and full shoe benders. + +### 358.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. + +### 358.28 Reaming and Threading. + +#### 358.28(A) Reaming. + +All cut ends of EMT shall be reamed or otherwise finished to remove rough edges. + +#### 358.28(B) Threading. + +EMT shall not be threaded. + +> [!important] Exception: +> EMT with factory threaded integral couplings complying with 358.100. + +### 358.30 Securing and Supporting. + +EMT shall be installed as a complete system in accordance with 300.18 and shall be securely fastened in place and supported in accordance with 358.30(A) and (B). + +#### 358.30(A) Securely Fastened. + +EMT shall be securely fastened in place at intervals not to exceed 3 m (10 ft). In addition, each EMT run between termination points shall be securely fastened within 900 mm (3 ft) of each outlet box, junction box, device box, cabinet, conduit body, or other tubing termination. + +> [!important] Exception No. 1: +> Fastening of unbroken lengths shall be permitted to be increased to a distance of 1.5 m (5 ft) where structural members do not readily permit fastening within 900 mm (3 ft). + +> [!important] Exception No. 2: +> For concealed work in finished buildings or prefinished wall panels where such securing is impracticable, unbroken lengths (without coupling) of EMT shall be permitted to be fished. + +#### 358.30(B) Supports. + +Horizontal runs of EMT supported by openings through framing members at intervals not greater than 3 m (10 ft) and securely fastened within 900 mm (3 ft) of termination points shall be permitted. + +### 358.42 Couplings and Connectors. + +Couplings and connectors used with EMT shall be made up tight. Where buried in masonry or concrete, they shall be concretetight type. Where installed in wet locations, they shall comply with 314.15. + +### 358.56 Splices and Taps. + +Splices and taps shall be made in accordance with 300.15. + +### 358.60 Grounding. + +EMT shall be permitted as an equipment grounding conductor. + +## Part III. Construction Specifications + +### 358.100 Construction. + +EMT shall be made of one of the following: + +* (1) Steel with protective coatings + +* (2) Aluminum + +* (3) Stainless steel + +### 358.120 Marking. + +EMT shall be clearly and durably marked at least every 3 m (10 ft) as required in the first sentence of 110.21(A). + +# Article 360 Flexible Metallic Tubing: Type FMT + +## Part I. General + +### 360.1 Scope. + +This article covers the use, installation, and construction specifications for flexible metallic tubing (FMT) and associated fittings. + +### 360.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Flexible Metallic Tubing (FMT). + +A metal raceway that is circular in cross section, flexible, and liquidtight without a nonmetallic jacket. + +### 360.6 Listing Requirements. + +FMT and associated fittings shall be listed. + +## Part II. Installation + +### 360.10 Uses Permitted. + +FMT shall be permitted to be used for branch circuits as follows: + +* (1) In dry locations + +* (2) Where concealed + +* (3) In accessible locations + +* (4) For system voltages of 1000 volts maximum + +### 360.12 Uses Not Permitted. + +FMT shall not be used as follows: + +* (1) In hoistways + +* (2) In storage battery rooms + +* (3) In hazardous (classified) locations unless otherwise permitted under other articles in this Code + +* (4) Underground for direct earth burial, or embedded in poured concrete or aggregate + +* (5) Where subject to physical damage + +* (6) In lengths over 1.8 m (6 ft) + +### 360.20 Size. + +#### 360.20(A) Minimum. + +FMT smaller than metric designator 16 (trade size 1⁄2) shall not be used. + +> [!important] Exception No. 1: +> FMT of metric designator 12 (trade size 3⁄8) shall be permitted to be installed in accordance with 300.22(B) and (C). + +> [!important] Exception No. 2: +> FMT of metric designator 12 (trade size 3⁄8) shall be permitted in lengths not in excess of 1.8 m (6 ft) as part of a listed assembly or for luminaires. See 410.117(C). + +#### 360.20(B) Maximum. + +The maximum size of FMT shall be metric designator 21 (trade size 3⁄4). + +> [!info] Informational Note: +> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions. + +### 360.22 Number of Conductors. + +#### 360.22(A) FMT — Metric Designators 16 and 21 (Trade Sizes 1⁄2 and 3⁄4). + +The number of conductors in metric designators 16 (trade size 1⁄2) and 21 (trade size 3⁄4) shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9. + +Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +#### 360.22(B) FMT — Metric Designator 12 (Trade Size 3⁄8). + +The number of conductors in metric designator 12 (trade size 3⁄8) shall not exceed that permitted in Table 348.22. + +### 360.24 Bends. + +#### 360.24(A) Infrequent Flexing Use. + +When FMT is infrequently flexed in service after installation, the radii of bends measured to the inside of the bend shall not be less than specified in Table 360.24(A). + +Table 360.24(A) Minimum Radii for Flexing Use + +Metric Designator + +Minimum Radii for Flexing Use + +Trade Size mm in. +12 3⁄8 254.0 10 +16 1⁄2 317.5 121⁄2 +21 3⁄4 444.5 171⁄2 + +#### 360.24(B) Fixed Bends. + +Where FMT is bent for installation purposes and is not flexed or bent as required by use after installation, the radii of bends measured to the inside of the bend shall not be less than specified in Table 360.24(B). + +Table 360.24(B) Minimum Radii for Fixed Bends + +Metric Designator + +Minimum Radii for + +Fixed Bends + +Trade Size mm in. +12 3⁄8 88.9 31⁄2 +16 1⁄2 101.6 4 +21 3⁄4 127.0 5 + +### 360.56 Splices and Taps. + +Splices and taps shall be made in accordance with 300.15. + +### 360.60 Grounding. + +FMT shall be permitted as an equipment grounding conductor where installed in accordance with 250.118(7). + +## Part III. Construction Specifications + +### 360.120 Marking. + +FMT shall be marked according to 110.21. + +# Article 362 Electrical Nonmetallic Tubing: Type ENT + +## Part I. General + +### 362.1 Scope. + +This article covers the use, installation, and construction specifications for electrical nonmetallic tubing (ENT) and associated fittings. + +### 362.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Electrical Nonmetallic Tubing (ENT). + +A nonmetallic, pliable, corrugated raceway of circular cross section with integral or associated couplings, connectors, and fittings for the installation of electrical conductors. ENT is composed of a material that is resistant to moisture and chemical atmospheres and is flame retardant. + +A pliable raceway is a raceway that can be bent by hand with a reasonable force but without other assistance. + +### 362.6 Listing Requirements. + +ENT and associated fittings shall be listed. + +## Part II. Installation + +### 362.10 Uses Permitted. + +For the purpose of this article, the first floor of a building shall be that floor that has 50 percent or more of the exterior wall surface area level with or above finished grade. One additional level that is the first level and not designed for human habitation and used only for vehicle parking, storage, or similar use shall be permitted. The use of ENT and fittings shall be permitted in the following: + +* (1) In any building not exceeding three floors above grade as follows: + * a. For exposed work, where not prohibited by 362.12 + * b. Concealed within walls, floors, and ceilings + +* (2) In any building exceeding three floors above grade, ENT shall be concealed within walls, floors, and ceilings where the walls, floors, and ceilings provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of firerated assemblies. The 15-minute-finish-rated thermal barrier shall be permitted to be used for combustible or noncombustible walls, floors, and ceilings. + +Exception to (2): Where a fire sprinkler system(s) is installed in accordance with NFPA 13-2016, Standard for the Installation of + +Sprinkler Systems, on all floors, ENT shall be permitted to be used within walls, floors, and ceilings, exposed or concealed, in buildings exceeding three floors abovegrade. + +> [!info] Informational Note: +> A finish rating is established for assemblies containing combustible (wood) supports. The finish rating is defined as the time at which the wood stud or wood joist reaches an average temperature rise of 121°C (250°F) or an individual temperature of 163°C (325°F) as measured on the plane of the wood nearest the fire. A finish rating is not intended to represent a rating for a membrane ceiling. + +* (3) In locations subject to severe corrosive influences as covered in 300.6 and where subject to chemicals for which the materials are specifically approved. + +* (4) In concealed, dry, and damp locations not prohibited by 362.12. + +* (5) Above suspended ceilings where the suspended ceilings provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies, except as permitted in 362.10(1)a. + +Exception to (5): ENT shall be permitted to be used above suspended ceilings in buildings exceeding three floors above grade where the building is protected throughout by a fire sprinkler system installed in accordance with NFPA 13-2016, Standard for the Installation of Sprinkler Systems. + +* (6) Encased in poured concrete, or embedded in a concrete slab on grade where ENT is placed on sand or approved screenings, provided fittings identified for this purpose are used for connections. + +* (7) For wet locations indoors as permitted in this section or in a concrete slab on or belowgrade, with fittings listed for the purpose. + +* (8) Metric designator 16 through 27 (trade size 1⁄2 through 1) as listed manufactured prewired assembly. + +* (9) Conductors or cables rated at a temperature higher than the listed temperature rating of ENT shall be permitted to be installed in + +ENT, if the conductors or cables are not operated at a temperature higher than the listed temperature rating of the ENT. + +### 362.12 Uses Not Permitted. + +ENT shall not be used in the following: + +* (1) In any hazardous (classified) location, except as permitted by other articles in this Code + +* (2) For the support of luminaires and other equipment + +* (3) Where subject to ambient temperatures in excess of 50°C (122°F) unless listed otherwise + +* (4) For direct earth burial + +* (5) In exposed locations, except as permitted by 362.10(1), 362.10(5), and 362.10(7) + +* (6) In theaters and similar locations, except as provided in 518.4 and 520.5 + +* (7) Where exposed to the direct rays of the sun, unless identified as sunlight resistant + +* (8) Where subject to physical damage + +> [!info] Informational Note: +> Extreme cold may cause some types of nonmetallic conduits to become brittle and therefore more susceptible to damage from physical contact. + +### 362.20 Size. + +#### 362.20(A) Minimum. + +ENT smaller than metric designator 16 (trade size 1⁄2) shall not be used. + +#### 362.20(B) Maximum. + +ENT larger than metric designator 63 (trade size 21⁄2) shall not be used. + +> [!info] Informational Note: +> See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions. + +### 362.22 Number of Conductors. + +The number of conductors shall not exceed that permitted by the percentage fill in Table 1, Chapter 9. + +Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9. + +### 362.24 Bends — How Made. + +Bends shall be so made that the tubing will not be damaged and the internal diameter of the tubing will not be effectively reduced. + +Bends shall be permitted to be made manually without auxiliary equipment, and the radius of the curve to the centerline of such bends shall not be less than shown in Table 2, Chapter 9 using the column “Other Bends.” + +### 362.26 Bends — Number in One Run. + +There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes. + +### 362.28 Trimming. + +All cut ends shall be trimmed inside and outside to remove rough edges. + +### 362.30 Securing and Supporting. + +ENT shall be installed as a complete system in accordance with 300.18 and shall be securely fastened in place by an approved means and supported in accordance with 362.30(A) and (B). + +#### 362.30(A) Securely Fastened. + +ENT shall be securely fastened at intervals not exceeding 900 mm (3 ft). In addition, ENT shall be securely fastened in place within +900 mm (3 ft) of each outlet box, device box, junction box, cabinet, or fitting where it terminates. Where used, cable ties shall be listed for the application and for securing and supporting. + +> [!important] Exception No. 1: +> Lengths not exceeding a distance of 1.8 m (6 ft) from a luminaire terminal connection for tap connections to lighting luminaires shall be permitted without being secured. + +> [!important] Exception No. 2: +> Lengths not exceeding 1.8 m (6 ft) from the last point where the raceway is securely fastened for connections within an accessible ceiling to luminaire(s) or other equipment. + +> [!important] Exception No. 3: +> For concealed work in finished buildings or prefinished wall panels where such securing is impracticable, unbroken lengths (without coupling) of ENT shall be permitted to be fished. + +#### 362.30(B) Supports. + +Horizontal runs of ENT supported by openings in framing members at intervals not exceeding 900 mm (3 ft) and securely fastened within 900 mm (3 ft) of termination points shall be permitted. + +### 362.46 Bushings. + +Where a tubing enters a box, fitting, or other enclosure, a bushing or adapter shall be provided to protect the wire from abrasion unless the box, fitting, or enclosure design provides equivalent protection. + +> [!info] Informational Note: +> See 300.4(G) for the protection of conductors size 4 AWG or larger. + +### 362.48 Joints. + +All joints between lengths of tubing and between tubing and couplings, fittings, and boxes shall be by an approved method. + +### 362.56 Splices and Taps. + +Splices and taps shall be made only in accordance with 300.15. + +> [!info] Informational Note: +> See Article 314 for rules on the installation and use of boxes and conduit bodies. + +### 362.60 Grounding. + +Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the raceway in compliance with Article 250, Part VI. + +## Part III. Construction Specifications + +### 362.100 Construction. + +ENT shall be made of material that does not exceed the ignitibility, flammability, smoke generation, and toxicity characteristics of rigid +(nonplasticized) polyvinyl chloride. + +ENT, as a prewired manufactured assembly, shall be provided in continuous lengths capable of being shipped in a coil, reel, or carton without damage. + +### 362.120 Marking. + +ENT shall be clearly and durably marked at least every 3 m (10 ft) as required in the first sentence of 110.21(A). The type of material shall also be included in the marking. Marking for limited smoke shall be permitted on the tubing that has limited smoke-producing characteristics. + +The type, size, and quantity of conductors used in prewired manufactured assemblies shall be identified by means of a printed tag or label attached to each end of the manufactured assembly and either the carton, coil, or reel. The enclosed conductors shall be marked in accordance with 310.8. + +# Article 366 Auxiliary Gutters + +## Part I. General + +### 366.1 Scope. + +This article covers the use, installation, and construction requirements of metal auxiliary gutters and nonmetallic auxiliary gutters and associated fittings. + +### 366.2 Definitions. + +The definitions in this section shall apply within this article and throughout the Code. + +Metal Auxiliary Gutter. + +A sheet metal enclosure used to supplement wiring spaces at meter centers, distribution centers, switchgear, switchboards, and similar points of wiring systems. The enclosure has hinged or removable covers for housing and protecting electrical wires, cable, and busbars. + +The enclosure is designed for conductors to be laid or set in place after the enclosures have been installed as a complete system. + +Nonmetallic Auxiliary Gutter. + +A flame-retardant, nonmetallic enclosure used to supplement wiring spaces at meter centers, distribution centers, switchgear, switchboards, and similar points of wiring systems. The enclosure has hinged or removable covers for housing and protecting electrical wires, cable, and busbars. The enclosure is designed for conductors to be laid or set in place after the enclosures have been installed as a complete system. + +### 366.6 Listing Requirements. + +#### 366.6(A) Outdoors. + +Nonmetallic auxiliary gutters installed outdoors shall be listed for all of the following conditions: + +* (1) Exposure to sunlight + +* (2) Use in wet locations + +* (3) Maximum ambient temperature of the installation + +#### 366.6(B) Indoors. + +Nonmetallic auxiliary gutters installed indoors shall be listed for the maximum ambient temperature of the installation. + +## Part II. Installation + +### 366.10 Uses Permitted. + +366.10(A) Sheet Metal Auxiliary Gutters. + +##### 366.10(A)(1) Indoor and Outdoor Use. + +Sheet metal auxiliary gutters shall be permitted for indoor and outdoor use. + +##### 366.10(A)(2) Wet Locations. + +Sheet metal auxiliary gutters installed in wet locations shall be suitable for such locations. + +#### 366.10(B) Nonmetallic Auxiliary Gutters. + +Nonmetallic auxiliary gutters shall be listed for the maximum ambient temperature of the installation and marked for the installed conductor insulation temperature rating. + +> [!info] Informational Note: +> Extreme cold may cause nonmetallic auxiliary gutters to become brittle and therefore more susceptible to damage from physical contact. + +##### 366.10(B)(1) Outdoors. + +Nonmetallic auxiliary gutters shall be permitted to be installed outdoors where listed and marked as suitable for the purpose. + +##### 366.10(B)(2) Indoors. + +Nonmetallic auxiliary gutters shall be permitted to be installed indoors. + +### 366.12 Uses Not Permitted. + +Auxiliary gutters shall not be used: + +* (1) To enclose switches, overcurrent devices, appliances, or other similar equipment + +* (2) To extend a greater distance than 9 m (30 ft) beyond the equipment that it supplements + +> [!important] Exception: +> As permitted in 620.35 for elevators, an auxiliary gutter shall be permitted to extend a distance greater than 9 m (30 ft) beyond the equipment it supplements. + +> [!info] Informational Note: +> For wireways, see Articles 376 and 378. For busways, see Article 368. + +### 366.20 Conductors Connected in Parallel. + +Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(G), the conductors shall be installed in groups consisting of not more than one conductor per phase, neutral, or grounded conductor to prevent current imbalance in the paralleled conductors due to inductive reactance. + +### 366.22 Number of Conductors. + +#### 366.22(A) Sheet Metal Auxiliary Gutters. + +The sum of the cross-sectional areas of all contained conductors and cables at any cross section of a sheet metal auxiliary gutter shall not exceed 20 percent of the interior cross-sectional area of the sheet metal auxiliary gutter. + +#### 366.22(B) Nonmetallic Auxiliary Gutters. + +The sum of cross-sectional areas of all contained conductors and cables at any cross section of the nonmetallic auxiliary gutter shall not exceed 20 percent of the interior cross-sectional area of the nonmetallic auxiliary gutter. + +### 366.23 Ampacity of Conductors. + +#### 366.23(A) Sheet Metal Auxiliary Gutters. + +The adjustment factors in 310.15(C)(1) shall be applied only where the number of current-carrying conductors, including neutral conductors clas sified as current-carrying under 310.15(E), exceeds 30 at any cross section of the sheet metal auxiliary gutter. + +Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors. The current carried continuously in bare copper bars in sheet metal auxiliary gutters shall not exceed 1.55 amperes/mm (1000 amperes/in. ) of cross section of the conductor. For aluminum bars, the current carried continuously shall not exceed 1.09 amperes/mm (700 amperes/in. ) of cross section of the conductor. + +#### 366.23(B) Nonmetallic Auxiliary Gutters. + +The adjustment factors specified in 310.15(C)(1) shall be applicable to the current-carrying conductors up to and including the 20 percent fill specified in 366.22(B). + +### 366.30 Securing and Supporting. + +#### 366.30(A) Sheet Metal Auxiliary Gutters. + +Sheet metal auxiliary gutters shall be supported and secured throughout their entire length at intervals not exceeding 1.5 m (5 ft). + +#### 366.30(B) Nonmetallic Auxiliary Gutters. + +Nonmetallic auxiliary gutters shall be supported and secured at intervals not to exceed 900 mm (3 ft) and at each end or joint, unless listed for other support intervals. In no case shall the distance between supports exceed 3 m (10 ft). + +### 366.44 Expansion Fittings. + +Expansion fittings shall be installed where expected length change, due to expansion and contraction due to temperature change, is more than 6 mm (0.25 in.). + +### 366.56 Splices and Taps. + +Splices and taps shall comply with 366.56(A) through (D). + +#### 366.56(A) Within Gutters. + +Splices or taps shall be permitted within gutters where they are accessible by means of removable covers or doors. The conductors, including splices and taps, shall not fill the gutter to more than 75 percent of its area. + +#### 366.56(B) Bare Conductors. + +Taps from bare conductors shall leave the gutter opposite their terminal connections, and conductors shall not be brought in contact with uninsulated current-carrying parts of different voltages. + +#### 366.56(C) Suitably Identified. + +All taps shall be suitably identified at the gutter as to the circuit or equipment that they supply. + +#### 366.56(D) Overcurrent Protection. + +2 2 +2 2 + +Tap connections from conductors in auxiliary gutters shall be provided with overcurrent protection as required in 240.21. + +### 366.58 Insulated Conductors. + +#### 366.58(A) Deflected Insulated Conductors. + +Where insulated conductors are deflected within an auxiliary gutter, either at the ends or where conduits, fittings, or other raceways or cables enter or leave the gutter, or where the direction of the gutter is deflected greater than 30 degrees, dimensions corresponding to one wire per terminal in Table 312.6(A) shall apply. + +#### 366.58(B) Auxiliary Gutters Used as Pull Boxes. + +Where insulated conductors 4 AWG or larger are pulled through an auxiliary gutter, the distance between raceway and cable entries enclosing the same conductor shall not be less than that required in 314.28(A)(1) for straight pulls and 314.28(A)(2) for angle pulls. + +### 366.60 Grounding. + +Metal auxiliary gutters shall be connected to an equipment grounding conductor(s), to an equipment bonding jumper, or to the grounded conductor where permitted or required by 250.92(B)(1) or 250.142. + +## Part III. Construction Specifications + +### 366.100 Construction. + +#### 366.100(A) Electrical and Mechanical Continuity. + +Gutters shall be constructed and installed so that adequate electrical and mechanical continuity of the complete system is secured. + +#### 366.100(B) Substantial Construction. + +Gutters shall be of substantial construction and shall provide a complete enclosure for the contained conductors. All surfaces, both interior and exterior, shall be suitably protected from corrosion. Corner joints shall be made tight, and where the assembly is held together by rivets, bolts, or screws, such fasteners shall be spaced not more than 300 mm (12 in.) apart. + +#### 366.100(C) Smooth Rounded Edges. + +Suitable bushings, shields, or fittings having smooth, rounded edges shall be provided where conductors pass between gutters, through partitions, around bends, between gutters and cabinets or junction boxes, and at other locations where necessary to prevent abrasion of the insulation of the conductors. + +#### 366.100(D) Covers. + +Covers shall be securely fastened to the gutter. + +#### 366.100(E) Clearance of Bare Live Parts. + +Bare conductors shall be securely and rigidly supported so that the minimum clearance between bare current-carrying metal parts of different voltages mounted on the same surface will not be less than 50 mm (2 in.), nor less than 25 mm (1 in.) for parts that are held free in the air. A clearance not less than 25 mm (1 in.) shall be secured between bare current-carrying metal parts and any metal surface. Adequate provisions shall be made for the expansion and contraction of busbars. + +### 366.120 Marking. + +#### 366.120(A) Outdoors. + +Nonmetallic auxiliary gutters installed outdoors shall have the following markings: + +* (1) Suitable for exposure to sunlight + +* (2) Suitable for use in wet locations + +* (3) Installed conductor insulation temperature rating + +#### 366.120(B) Indoors. + +Nonmetallic auxiliary gutters installed indoors shall be marked with the installed conductor insulation temperature rating. + +# Article 368 Busways + +## Part I. General Requirements + +### 368.1 Scope. + +This article covers service-entrance, feeder, and branch-circuit busways and associated fittings. + +### 368.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Busway. + +A raceway consisting of a metal enclosure containing factory-mounted, bare or insulated conductors, which are usually copper or aluminum bars, rods, or tubes. + +> [!info] Informational Note: +> For cablebus, refer to Article 370. + +## Part II. Installation + +### 368.10 Uses Permitted. + +Busways shall be permitted to be installed where they are located in accordance with 368.10(A) through (C). + +> [!info] Informational Note: +> See 300.21 for information concerning the spread of fire or products of combustion. + +#### 368.10(A) Exposed. + +Busways shall be permitted to be located in the open where visible, except as permitted in 368.10(C). + +#### 368.10(B) Behind Access Panels. + +Busways shall be permitted to be installed behind access panels, provided the busways are totally enclosed, of nonventilating-type construction, and installed so that the joints between sections and at fittings are accessible for maintenance purposes. Where installed behind access panels, means of access shall be provided, and either of the following conditions shall be met: + +* (1) The space behind the access panels shall not be used for air-handling purposes. + +* (2) Where the space behind the access panels is used for environmental air, other than ducts and plenums, there shall be no provisions for plug-in connections, and the conductors shall be insulated. + +#### 368.10(C) Through Walls and Floors. + +Busways shall be permitted to be installed through walls or floors in accordance with (C)(1) and (C)(2). + +##### 368.10(C)(1) Walls. + +Unbroken lengths of busway shall be permitted to be extended through dry walls. + +##### 368.10(C)(2) Floors. + +Floor penetrations shall comply with (a) and (b): + +* (a) Busways shall be permitted to be extended vertically through dry floors if totally enclosed (unventilated) where passing through and for a minimum distance of 1.8 m (6 ft) above the floor to provide adequate protection from physical damage. + +* (b) In other than industrial establishments, where a vertical riser penetrates two or more dry floors, a minimum 100-mm (4-in.) high curb shall be installed around all floor openings for riser busways to prevent liquids from entering the opening. The curb shall be installed within 300 mm (12 in.) of the floor opening. Electrical equipment shall be located so that it will not be damaged by liquids that are retained by the curb. + +### 368.12 Uses Not Permitted. + +#### 368.12(A) Physical Damage. + +Busways shall not be installed where subject to severe physical damage or corrosive vapors. + +#### 368.12(B) Hoistways. + +Busways shall not be installed in hoistways. + +#### 368.12(C) Hazardous Locations. + +Busways shall not be installed in any hazardous (classified) location, unless specifically approved for such use. + +> [!info] Informational Note: +> See 501.10(B). + +#### 368.12(D) Wet Locations. + +Busways shall not be installed outdoors or in wet or damp locations unless identified for such use. + +#### 368.12(E) Working Platform. + +Lighting busway and trolley busway shall not be installed less than 2.5 m (8 ft) above the floor or working platform unless provided with an identified cover. + +### 368.17 Overcurrent Protection. + +Overcurrent protection shall be provided in accordance with 368.17(A) through (D). + +#### 368.17(A) Rating of Overcurrent Protection — Feeders. + +A busway shall be protected against overcurrent in accordance with the current rating of the busway. + +> [!important] Exception No. 1: +> The applicable provisions of 240.4 shall be permitted. + +> [!important] Exception No. 2: +> Where used as transformer secondary ties, 450.6(A) (3) shall be permitted. + +#### 368.17(B) Reduction in Ampacity Size of Busway. + +Overcurrent protection shall be required where busways are reduced in ampacity. + +> [!important] Exception: +> For industrial establishments only, omission of overcurrent protection shall be permitted at points where busways are reduced in ampacity, provided that the length of the busway having the smaller ampacity does not exceed 15 m (50 ft) and has an ampacity at least equal to one-third the rating or setting of the overcurrent device next back on the line, and provided that such busway is free from contact with combustible material. + +#### 368.17(C) Feeder or Branch Circuits. + +Where a busway is used as a feeder, devices or plug-in connections for tapping off feeder or branch circuits from the busway shall contain the overcurrent devices required for the protection of the feeder or branch circuits. The plug-in device shall consist of an externally operable circuit breaker or an externally operable fusible switch. Where such devices are mounted out of reach and contain disconnecting means, suitable means such as ropes, chains, or sticks shall be provided for operating the disconnecting means from the floor. + +> [!important] Exception No. 1: +> As permitted in 240.21. + +> [!important] Exception No. 2: +> For fixed or semifixed luminaires, where the branch-circuit overcurrent device is part of the luminaire cord plug on cord-connected luminaires. + +> [!important] Exception No. 3: +> Where luminaires without cords are plugged directly into the busway and the overcurrent device is mounted on the luminaire. + +> [!important] Exception No. 4: +> Where the branch-circuit overcurrent plug-in device is directly supplying a readily accessible disconnect, a method of floor operation shall not be required. + +#### 368.17(D) Rating of Overcurrent Protection — Branch Circuits. + +A busway used as a branch circuit shall be protected against overcurrent in accordance with 210.20. + +### 368.30 Support. + +Busways shall be securely supported at intervals not exceeding 1.5 m (5 ft) unless otherwise designed and marked. + +### 368.56 Branches from Busways. + +Branches from busways shall be permitted to be made in accordance with 368.56(A), (B), and (C). + +#### 368.56(A) General. + +Branches from busways shall be permitted to use any of the following wiring methods: + +* (1) Type AC armored cable + +* (2) Type MC metal-clad cable + +* (3) Type MI mineral-insulated, metal-sheathed cable + +* (4) Type IMC intermediate metal conduit + +* (5) Type RMC rigid metal conduit + +* (6) Type FMC flexible metal conduit + +* (7) Type LFMC liquidtight flexible metal conduit + +* (8) Type PVC rigid polyvinyl chloride conduit + +* (9) Type RTRC reinforced thermosetting resin conduit + +* (10) Type LFNC liquidtight flexible nonmetallic conduit + +* (11) Type EMT electrical metallic tubing + +* (12) Type ENT electrical nonmetallic tubing + +* (13) Busways + +* (14) Strut-type channel raceway + +* (15) Surface metal raceway + +* (16) Surface nonmetallic raceway + +Where a separate equipment grounding conductor is used, connection of the equipment grounding conductor to the busway shall comply with 250.8 and 250.12. + +#### 368.56(B) Cord and Cable Assemblies. + +Suitable cord and cable assemblies identified for extra-hard usage or hard usage and listed bus drop cable shall be permitted as branches from busways for the connection of portable equipment or the connection of stationary equipment to facilitate their interchange in accordance with 400.10 and 400.12 and the following conditions: + +* (1) The cord or cable shall be attached to the building by an approved means. + +* (2) The length of the cord or cable from a busway plug-in device to a suitable tension take-up support device shall not exceed 1.8 m +(6 ft). + +* (3) The cord and cable shall be installed as a vertical riser from the tension take-up support device to the equipment served. + +* (4) Strain relief cable grips shall be provided for the cord or cable at the busway plug-in device and equipment terminations. + +Exception to (B)(2): In industrial establishments only, where the conditions of maintenance and supervision ensure that only qualified persons service the installation, lengths exceeding 1.8 m (6 ft) shall be permitted between the busway plug-in device and the tension take-up support device where the cord or cable is supported at intervals not exceeding 2.5 m (8 ft). + +#### 368.56(C) Branches from Trolley-Type Busways. + +Suitable cord and cable assemblies identified for extra-hard usage or hard usage and listed bus drop cable shall be permitted as branches from trolley-type busways for the connection of movable equipment in accordance with 400.10 and 400.12. + +### 368.58 Dead Ends. + +A dead end of a busway shall be closed. + +### 368.60 Grounding. + +Busway shall be connected to an equipment grounding conductor(s), to an equipment bonding jumper, or to the grounded conductor where permitted or required by 250.92(B)(1) or 250.142. + +## Part III. Construction + +### 368.120 Marking. + +Busways shall be marked with the voltage and current rating for which they are designed, and with the manufacturer's name or trademark in such a manner as to be visible after installation. + +## Part IV. Requirements for Over 1000 Volts, Nominal + +### 368.214 Adjacent and Supporting Structures. + +Metal-enclosed busways shall be installed so that temperature rise from induced circulating currents in adjacent ferrous metal parts will not be hazardous to personnel or constitute a fire hazard. + +### 368.234 Barriers and Seals. + +#### 368.234(A) Vapor Seals. + +Busway runs that have sections located both inside and outside of buildings shall have a vapor seal at the building wall to prevent interchange of air between indoor and outdoor sections. + +> [!important] Exception: +> Vapor seals shall not be required in forced-cooled bus. + +#### 368.234(B) Fire Barriers. + +Fire barriers shall be provided where fire walls, floors, or ceilings are penetrated. + +> [!info] Informational Note: +> See 300.21 for information concerning the spread of fire or products of combustion. + +### 368.236 Drain Facilities. + +Drain plugs, filter drains, or similar methods shall be provided to remove condensed moisture from low points in busway run. + +### 368.237 Ventilated Bus Enclosures. + +Ventilated busway enclosures shall be installed in accordance with Article 110, Part III, and 490.24. + +### 368.238 Terminations and Connections. + +Where bus enclosures terminate at machines cooled by flammable gas, seal-off bushings, baffles, or other means shall be provided to prevent accumulation of flammable gas in the busway enclosures. + +All conductor termination and connection hardware shall be accessible for installation, connection, and maintenance. + +### 368.239 Switches. + +Switching devices or disconnecting links provided in the busway run shall have the same momentary rating as the busway. + +Disconnecting links shall be plainly marked to be removable only when bus is de-energized. Switching devices that are not load-break shall be interlocked to prevent operation under load, and disconnecting link enclosures shall be interlocked to prevent access to energized parts. + +### 368.240 Wiring 1000 Volts or Less, Nominal. + +Secondary control devices and wiring that are provided as part of the metal-enclosed bus run shall be insulated by fire-retardant barriers from all primary circuit elements with the exception of short lengths of wire, such as at instrument transformer terminals. + +### 368.244 Expansion Fittings. + +Flexible or expansion connections shall be provided in long, straight runs of bus to allow for temperature expansion or contraction, or where the busway run crosses building vibration insulation joints. + +### 368.258 Neutral Conductor. + +Neutral bus, where required, shall be sized to carry all neutral load current, including harmonic currents, and shall have adequate momentary and short-circuit current rating consistent with system requirements. + +### 368.260 Grounding. + +Metal-enclosed busway shall be grounded. + +### 368.320 Marking. + +Each busway run shall be provided with a permanent nameplate on which the following information shall be provided: + +* (1) Rated voltage. + +* (2) Rated continuous current; if bus is forced-cooled, both the normal forced-cooled rating and the self-cooled (not forced-cooled) rating for the same temperature rise shall be given. + +* (3) Rated frequency. + +* (4) Rated impulse withstand voltage. + +* (5) Rated 60-Hz withstand voltage (dry). + +* (6) Rated momentary current. + +* (7) Manufacturer's name or trademark. + +> [!info] Informational Note: +> See IEEE C37.23-2015, IEEE Standard for Metal-Enclosed Bus, for construction and testing requirements for metal-enclosed bus assemblies. + +# Article 370 Cablebus + +## Part I. General + +### 370.1 Scope. + +This article covers the use and installation requirements of cablebus and associated fittings. + +### 370.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Cablebus. + +An assembly of units or sections with insulated conductors having associated fittings forming a structural system used to securely fasten or support conductors and conductor terminations in a completely enclosed, ventilated, protective metal housing. This assembly is designed to carry fault current and to withstand the magnetic forces of such current. + +> [!info] Informational Note: +> Cablebus is ordinarily assembled at the point of installation from the components furnished or specified by the manufacturer in accordance with instructions for the specific job. + +## Part II. Installation + +### 370.10 Uses Permitted. + +Approved cablebus shall be permitted: + +* (1) At any voltage or current for which spaced conductors are rated and where installed only for exposed work, except as permitted in 370.18 + +* (2) For branch circuits, feeders, and services + +* (3) To be installed outdoors or in corrosive, wet, or damp locations where identified for the use + +### 370.12 Uses Not Permitted. + +Cablebus shall not be permitted to be installed in the following: + +* (1) Hoistways + +* (2) Hazardous (classified) locations, unless specifically permitted in Chapter 5 + +### 370.18 Cablebus Installation. + +#### 370.18(A) Transversely Routed. + +Cablebus shall be permitted to extend transversely through partitions or walls, other than fire walls, provided that the section within the wall is continuous, protected against physical damage, and unventilated. + +#### 370.18(B) Through Dry Floors and Platforms. + +Except where firestops are required, cablebus shall be permitted to extend vertically through dry floors and platforms, provided that the cablebus is totally enclosed at the point where it passes through the floor or platform and for a distance of 1.8 m (6 ft) above the floor or platform. + +#### 370.18(C) Through Floors and Platforms in Wet Locations. + +Except where firestops are required, cablebus shall be permitted to extend vertically through floors and platforms in wet locations where: + +* (1) There are curbs or other suitable means to prevent waterflow through the floor or platform opening, and + +* (2) Where the cablebus is totally enclosed at the point where it passes through the floor or platform and for a distance of 1.8 m (6 ft) above the floor or platform. + +### 370.20 Conductor Size and Termination. + +#### 370.20(A) Conductors. + +The current-carrying conductors in cablebus shall: + +* (1) Have an insulation rating of 75°C (167°F) or higher and be of an approved type suitable for the application. + +* (2) Be sized in accordance with the design of the cablebus but in no case be smaller than 1/0. + +#### 370.20(B) Termination. + +Approved terminating means shall be used for connections to cablebus conductors. + +> [!info] Informational Note No. 1: +> See 110.14(C) for conductor temperature limitations due to termination provisions for installations up to and including 2000 volts. + +> [!info] Informational Note No. 2: +> See 110.40 for conductor temperature limitations due to termination provisions for installations 2001 volts to +35,000 volts. + +### 370.22 Number of Conductors. + +The number of conductors shall be that for which the cablebus is designed. + +### 370.23 Overcurrent Protection. + +Cablebus shall be protected against overcurrent in accordance with the ampacity of the cablebus conductors in accordance with 240.4. + +> [!important] Exception: +> Overcurrent protection shall be permitted in accordance with 240.100 and 240.101. + +### 370.30 Securing and Supporting. + +#### 370.30(A) Cablebus Supports. + +Cablebus shall be securely supported at intervals not exceeding 3.7 m (12 ft). Where spans longer than 3.7 m (12 ft) are required, the structure shall be specifically designed for the required span length. + +#### 370.30(B) Conductor Supports. + +The insulated conductors shall be supported on blocks or other identified mounting means. + +The individual conductors in a cablebus shall be supported at intervals not greater than 900 mm (3 ft) for horizontal runs and 450 mm +(11⁄2 ft) for vertical runs. Vertical and horizontal spacing between supported conductors shall be not less than one conductor diameter at the points of support. + +### 370.42 Fittings. + +A cablebus system shall include approved fittings for the following: + +* (1) Changes in horizontal or vertical direction of the run + +* (2) Dead ends + +* (3) Terminations in or on connected apparatus or equipment or the enclosures for such equipment + +* (4) Additional physical protection where required, such as guards where subject to severe physical damage + +### 370.60 Grounding. + +A cablebus system shall be grounded and/or bonded as applicable: + +* (1) Cablebus framework, where bonded, shall be permitted to be used as the equipment grounding conductor for branch circuits and feeders. + +* (2) A cablebus installation shall be grounded and bonded in accordance with Article 250, excluding 250.86, Exception No. 2. + +### 370.80 Ampacity of Conductors. + +The ampacity of conductors in cablebus shall be in accordance with 310.17 and 310.19 for installations up to and including 2000 volts, or with Table 311.60(C)(69) and Table 311.60(C)(70) for installations 2001 volts to 35,000 volts. + +## Part III. Construction Specifications + +### 370.120 Marking. + +Each section of cablebus shall be marked with the manufacturer's name or trade designation and the maximum diameter, number, voltage rating, and ampacity of the conductors to be installed. Markings shall be located so as to be visible after installation. + +# Article 372 Cellular Concrete Floor Raceways + +## Part I. General + +### 372.1 Scope. + +This article covers cellular concrete floor raceways, the hollow spaces in floors constructed of precast cellular concrete slabs, together with suitable metal fittings designed to provide access to the floor cells. + +### 372.2 Definitions. + +The definitions in this section shall apply only within this article. + +Cell. + +A single, enclosed tubular space in a floor made of precast cellular concrete slabs, the direction of the cell being parallel to the direction of the floor member. + +Header. + +Transverse metal raceways for electrical conductors, providing access to predetermined cells of a precast cellular concrete floor, thereby permitting the installation of electrical conductors from a distribution center to the floor cells. + +## Part II. Installations + +### 372.12 Uses Not Permitted. + +Conductors shall not be installed in precast cellular concrete floor raceways as follows: + +* (1) Where subject to corrosive vapor + +* (2) In any hazardous (classified) location, except as permitted by other articles in this Code + +* (3) In commercial garages, other than for supplying ceiling outlets or extensions to the area below the floor but not above + +> [!info] Informational Note: +> See 300.8 for installation of conductors with other systems. + +### 372.18 Cellular Concrete Floor Raceways Installation. + +Installation of cellular concrete floor raceways shall comply with 372.18(A) through 372.18(E). + +#### 372.18(A) Header. + +The header shall be installed in a straight line at right angles to the cells. The header shall be mechanically secured to the top of the precast cellular concrete floor. The end joints shall be closed by a metal closure fitting and sealed against the entrance of concrete. The header shall be electrically continuous throughout its entire length and shall be electrically bonded to the enclosure of the distribution center. + +#### 372.18(B) Connection to Cabinets and Other Enclosures. + +Connections from headers to cabinets and other enclosures shall be made by means of listed metal raceways and listed fittings. + +#### 372.18(C) Junction Boxes. + +Junction boxes shall be leveled to the floor grade and sealed against the free entrance of water or concrete. Junction boxes shall be of metal and shall be mechanically and electrically continuous with the header. + +#### 372.18(D) Inserts. + +Inserts shall be leveled and sealed against the entrance of concrete. Inserts shall be of metal and shall be fitted with grounded-type receptacles. An equipment grounding conductor or bonding jumper shall connect the insert receptacles to a positive ground connection provided on the header. Where cutting through the cell wall for setting inserts or other purposes (such as providing access openings between header and cells), chips and other dirt shall not be allowed to remain in the raceway, and the tool used shall be designed so as to prevent the tool from entering the cell and damaging the conductors. + +#### 372.18(E) Markers. + +A suitable number of markers shall be installed for the future location of cells. + +### 372.20 Size of Conductors. + +No conductor larger than 1/0 AWG shall be installed, except by special permission. + +### 372.22 Maximum Number of Conductors. + +The combined cross-sectional area of all conductors or cables shall not exceed 40 percent of the cross-sectional area of the cell or header. + +### 372.23 Ampacity of Conductors. + +The ampacity adjustment factors as provided in 310.15(C) shall apply to conductors installed in cellular concrete floor raceways. + +### 372.56 Splices and Taps. + +Splices and taps shall be made only in header access units or junction boxes. A continuous unbroken conductor connecting the individual outlets is not a splice or tap. + +### 372.58 Discontinued Outlets. + +When an outlet is abandoned, discontinued, or removed, the sections of circuit conductors supplying the outlet shall be removed from the raceway. No splices or reinsulated conductors, such as would be the case of abandoned outlets on loop wiring, shall be allowed in raceways. + +# Article 374 Cellular Metal Floor Raceways + +## Part I. General + +### 374.1 Scope. + +This article covers the use and installation requirements for cellular metal floor raceways. + +### 374.2 Definitions. + +The definitions in this section shall apply within this article and throughout the Code. + +Cellular Metal Floor Raceway. + +The hollow spaces of cellular metal floors, together with suitable fittings, that may be approved as enclosed channel for electrical conductors. + +Cell. + +A single enclosed tubular space in a cellular metal floor member, the axis of the cell being parallel to the axis of the metal floor member. + +Header. + +A transverse raceway for electrical conductors, providing access to predetermined cells of a cellular metal floor, thereby permitting the installation of electrical conductors from a distribution center to the cells. + +### 374.6 Listing Requirements. + +Cellular metal floor raceways shall be listed. + +## Part II. Installation + +### 374.12 Uses Not Permitted. + +Conductors shall not be installed in cellular metal floor raceways as follows: + +* (1) Where subject to corrosive vapor + +* (2) In any hazardous (classified) location, except as permitted by other articles in this Code + +* (3) In commercial garages, other than for supplying ceiling outlets or extensions to the area below the floor but not above + +> [!info] Informational Note: +> See 300.8 for installation of conductors with other systems. + +### 374.18 Cellular Metal Floor Raceways Installations. + +Installation of cellular metal floor raceways shall comply with 374.18(A) through 374.18(D). + +#### 374.18(A) Connection to Cabinets and Extensions from Cells. + +Connections between raceways and distribution centers and wall outlets shall be made by means of liquidtight flexible metal conduit, flexible metal conduit where not installed in concrete, rigid metal conduit, intermediate metal conduit, electrical metallic tubing, or approved fittings. Where there are provisions for the termination of an equipment grounding conductor, rigid polyvinyl chloride conduit, reinforced thermosetting resin conduit, electrical nonmetallic tubing, or liquidtight flexible nonmetallic conduit shall be permitted. Where installed in concrete, liquidtight flexible metal conduit and liquidtight flexible nonmetallic conduit shall be listed and marked for direct burial. + +#### 374.18(B) Junction Boxes. + +Junction boxes shall be leveled to the floor grade and sealed against the free entrance of water or concrete. Junction boxes used with these raceways shall be of metal and shall be electrically continuous with the raceway. + +#### 374.18(C) Inserts. + +Inserts shall be leveled to the floor grade and sealed against the entrance of concrete. Inserts shall be of metal and shall be electrically continuous with the raceway. In cutting through the cell wall and setting inserts, chips and other dirt shall not be allowed to remain in the raceway, and tools shall be used that are designed to prevent the tool from entering the cell and damaging the conductors. + +#### 374.18(D) Markers. + +A suitable number of markers shall be installed for locating cells in the future. + +### 374.20 Size of Conductors. + +No conductor larger than 1/0 AWG shall be installed, except by special permission. + +### 374.22 Maximum Number of Conductors in Raceway. + +The combined cross-sectional area of all conductors or cables shall not exceed 40 percent of the interior cross-sectional area of the cell or header. + +### 374.23 Ampacity of Conductors. + +The ampacity adjustment factors in 310.15(C) shall apply to conductors installed in cellular metal floor raceways. + +### 374.56 Splices and Taps. + +Splices and taps shall be made only in header access units or junction boxes. + +For the purposes of this section, so-called loop wiring (continuous unbroken conductor connecting the individual outlets) shall not be considered to be a splice or tap. + +### 374.58 Discontinued Outlets. + +When an outlet is abandoned, discontinued, or removed, the sections of circuit conductors supplying the outlet shall be removed from the raceway. No splices or reinsulated conductors, such as would be the case with abandoned outlets on loop wiring, shall be allowed in raceways. + +## Part III. Construction Specifications + +### 374.100 General. + +Cellular metal floor raceways shall be constructed so that adequate electrical and mechanical continuity of the complete system will be secured. They shall provide a complete enclosure for the conductors. The interior surfaces shall be free from burrs and sharp edges, and surfaces over which conductors are drawn shall be smooth. Suitable bushings or fittings having smooth rounded edges shall be provided where conductors pass. + +# Article 376 Metal Wireways + +## Part I. General + +### 376.1 Scope. + +This article covers the use, installation, and construction specifications for metal wireways and associated fittings. + +### 376.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Metal Wireways. + +Sheet metal troughs with hinged or removable covers for housing and protecting electrical wires and cable and in which conductors are laid in place after the raceway has been installed as a complete system. + +## Part II. Installation + +### 376.10 Uses Permitted. + +The use of metal wireways shall be permitted as follows: + +* (1) For exposed work. + +* (2) In any hazardous (classified) location, as permitted by other articles in this Code. + +* (3) In wet locations where wireways are listed for the purpose. + +* (4) In concealed spaces as an extension that passes transversely through walls, if the length passing through the wall is unbroken. + +Access to the conductors shall be maintained on both sides of the wall. + +### 376.12 Uses Not Permitted. + +Metal wireways shall not be used in the following: + +* (1) Where subject to severe physical damage + +* (2) Where subject to severe corrosive environments + +### 376.20 Conductors Connected in Parallel. + +Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(G), the conductors shall be installed in groups consisting of not more than one conductor per phase, neutral, or grounded conductor. + +> [!info] Informational Note: +> The purpose of having all parallel conductor sets within the same group is to prevent current imbalance in the paralleled conductors due to inductive reactance. + +### 376.21 Size of Conductors. + +No conductor larger than that for which the wireway is designed shall be installed in any wireway. + +### 376.22 Number of Conductors and Ampacity. + +The number of conductors or cables and their ampacity shall comply with 376.22(A) and (B). + +#### 376.22(A) Cross-Sectional Areas of Wireway. + +The sum of the cross-sectional areas of all contained conductors and cables at any cross section of a wireway shall not exceed +20 percent of the interior cross-sectional area of the wireway. + +#### 376.22(B) Adjustment Factors. + +The adjustment factors in 310.15(C) (1) shall be applied only where the number of current-carrying conductors, including neutral conductors classified as current-carrying under 310.15(E), exceeds 30 at any cross section of the wireway. Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as currentcarrying conductors. + +### 376.23 Insulated Conductors. + +Insulated conductors installed in a metal wireway shall comply with 376.23(A) and (B). + +#### 376.23(A) Deflected Insulated Conductors. + +Where insulated conductors are deflected within a metal wireway, either at the ends or where conduits, fittings, or other raceways or cables enter or leave the metal wireway, or where the direction of the metal wireway is deflected greater than 30 degrees, dimensions corresponding to one wire per terminal in Table 312.6(A) shall apply. + +#### 376.23(B) Metal Wireways Used as Pull Boxes. + +Where insulated conductors 4 AWG or larger are pulled through a wireway, the distance between raceway and cable entries enclosing the same conductor shall not be less than that required by 314.28(A)(1) for straight pulls and 314.28(A)(2) for angle pulls. When transposing cable size into raceway size, the minimum metric designator (trade size) raceway required for the number and size of conductors in the cable shall be used. + +### 376.30 Securing and Supporting. + +Metal wireways shall be supported in accordance with 376.30(A) and (B). + +#### 376.30(A) Horizontal Support. + +Wireways shall be supported where run horizontally at each end and at intervals not to exceed 1.5 m (5 ft) or for individual lengths longer than 1.5 m (5 ft) at each end or joint, unless listed for other support intervals. The distance between supports shall not exceed +3 m (10 ft). + +#### 376.30(B) Vertical Support. + +Vertical runs of wireways shall be securely supported at intervals not exceeding 4.5 m (15 ft) and shall not have more than one joint between supports. Adjoining wireway sections shall be securely fastened together to provide a rigid joint. + +### 376.56 Splices, Taps, and Power Distribution Blocks. + +#### 376.56(A) Splices and Taps. + +Splices and taps shall be permitted within a wireway, provided they are accessible. The conductors, including splices and taps, shall not fill the wireway to more than 75 percent of its area at that point. + +#### 376.56(B) Power Distribution Blocks. + +##### 376.56(B)(1) Installation. + +Power distribution blocks installed in metal wireways shall be listed. Power distribution blocks installed on the line side of the service equipment shall be marked “suitable for use on the line side of service equipment” or equivalent. + +##### 376.56(B)(2) Size of Enclosure. + +In addition to the wiring space requirement in 376.56(A), the power distribution block shall be installed in a wireway with dimensions not smaller than specified in the installation instructions of the power distribution block. + +##### 376.56(B)(3) Wire Bending Space. + +Wire bending space at the terminals of power distribution blocks shall comply with 312.6(B). + +##### 376.56(B)(4) Live Parts. + +Power distribution blocks shall not have uninsulated live parts exposed within a wireway, whether or not the wireway cover is installed. + +##### 376.56(B)(5) Conductors. + +Conductors shall be arranged so the power distribution block terminals are unobstructed following installation. + +### 376.58 Dead Ends. + +Dead ends of metal wireways shall be closed. + +### 376.70 Extensions from Metal Wireways. + +Extensions from wireways shall be made with cord pendants installed in accordance with 400.14 or with any wiring method in Chapter 3 that includes a means for equipment grounding. Where a separate equipment grounding conductor is employed, connection of the equipment grounding conductors in the wiring method to the wireway shall comply with 250.8 and 250.12. + +## Part III. Construction Specifications + +### 376.100 Construction. + +#### 376.100(A) Electrical and Mechanical Continuity. + +Wireways shall be constructed and installed so that electrical and mechanical continuity of the complete system are assured. + +#### 376.100(B) Substantial Construction. + +Wireways shall be of substantial construction and shall provide a complete enclosure for the contained conductors. All surfaces, both interior and exterior, shall be suitably protected from corrosion. Corner joints shall be made tight, and where the assembly is held together by rivets, bolts, or screws, such fasteners shall be spaced not more than 300 mm (12 in.) apart. + +#### 376.100(C) Smooth Rounded Edges. + +Suitable bushings, shields, or fittings having smooth, rounded edges shall be provided where conductors pass between wireways, through partitions, around bends, between wireways and cabinets or junction boxes, and at other locations where necessary to prevent abrasion of the insulation of the conductors. + +#### 376.100(D) Covers. + +Covers shall be securely fastened to the wireway. + +### 376.120 Marking. + +Metal wireways shall be so marked that their manufacturer’s name or trademark will be visible after installation. + +# Article 378 Nonmetallic Wireways + +## Part I. General + +### 378.1 Scope. + +This article covers the use, installation, and construction specifications for nonmetallic wireways and associated fittings. + +### 378.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Nonmetallic Wireways. + +Flame-retardant, nonmetallic troughs with removable covers for housing and protecting electrical wires and cables in which conductors are laid in place after the raceway has been installed as a complete system. + +### 378.6 Listing Requirements. + +Nonmetallic wireways and associated fittings shall be listed. + +## Part II. Installation + +### 378.10 Uses Permitted. + +The use of nonmetallic wireways shall be permitted in the following: + +* (1) Only for exposed work, except as permitted in 378.10(4). + +* (2) Where subject to corrosive environments where identified for the use. + +* (3) In wet locations where listed for the purpose. + +> [!info] Informational Note: +> Extreme cold may cause nonmetallic wireways to become brittle and therefore more susceptible to damage from physical contact. + +* (4) As extensions to pass transversely through walls if the length passing through the wall is unbroken. Access to the conductors shall be maintained on both sides of the wall. + +### 378.12 Uses Not Permitted. + +Nonmetallic wireways shall not be used in the following: + +* (1) Where subject to physical damage + +* (2) In any hazardous (classified) location, except as permitted by other articles in this Code + +* (3) Where exposed to sunlight unless listed and marked as suitable for the purpose + +* (4) Where subject to ambient temperatures other than those for which nonmetallic wireway is listed + +* (5) For conductors whose insulation temperature limitations would exceed those for which the nonmetallic wireway is listed + +### 378.20 Conductors Connected in Parallel. + +Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(G), the conductors shall be installed in groups consisting of not more than one conductor per phase, neutral, or grounded conductor to prevent current imbalance in the paralleled conductors due to inductive reactance. + +### 378.21 Size of Conductors. + +No conductor larger than that for which the nonmetallic wireway is designed shall be installed in any nonmetallic wireway. + +### 378.22 Number of Conductors. + +The sum of cross-sectional areas of all contained conductors or cables at any cross section of the nonmetallic wireway shall not exceed +20 percent of the interior cross-sectional area of the nonmetallic wireway. Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors. + +The adjustment factors specified in 310.15(C)(1) shall be applicable to the current-carrying conductors up to and including the +20 percent fill specified in the first paragraph of this section. + +### 378.23 Insulated Conductors. + +Insulated conductors installed in a nonmetallic wireway shall comply with 378.23(A) and (B). + +#### 378.23(A) Deflected Insulated Conductors. + +Where insulated conductors are deflected within a nonmetallic wireway, either at the ends or where conduits, fittings, or other raceways or cables enter or leave the nonmetallic wireway, or where the direction of the nonmetallic wireway is deflected greater than 30 degrees, dimensions corresponding to one wire per terminal in Table 312.6(A) shall apply. + +#### 378.23(B) Nonmetallic Wireways Used as Pull Boxes. + +Where insulated conductors 4 AWG or larger are pulled through a wireway, the distance between raceway and cable entries enclosing the same conductor shall not be less than that required in 314.28(A)(1) for straight pulls and in 314.28(A)(2) for angle pulls. When transposing cable size into raceway size, the minimum metric designator (trade size) raceway required for the number and size of conductors in the cable shall be used. + +### 378.30 Securing and Supporting. + +Nonmetallic wireway shall be supported in accordance with 378.30(A) and (B). + +#### 378.30(A) Horizontal Support. + +Nonmetallic wireways shall be supported where run horizontally at intervals not to exceed 900 mm (3 ft), and at each end or joint, unless listed for other support intervals. In no case shall the distance between supports exceed 3 m (10 ft). + +#### 378.30(B) Vertical Support. + +Vertical runs of nonmetallic wireway shall be securely supported at intervals not exceeding 1.2 m (4 ft), unless listed for other support intervals, and shall not have more than one joint between supports. Adjoining nonmetallic wireway sections shall be securely fastened together to provide a rigid joint. + +### 378.44 Expansion Fittings. + +Expansion fittings for nonmetallic wireway shall be provided to compensate for thermal expansion and contraction where the length change is expected to be 6 mm (0.25 in.) or greater in a straight run. + +> [!info] Informational Note: +> See Table 352.44 for expansion characteristics of PVC conduit. The expansion characteristics of PVC nonmetallic wireway are identical. + +### 378.56 Splices and Taps. + +Splices and taps shall be permitted within a nonmetallic wireway, provided they are accessible. The conductors, including splices and taps, shall not fill the nonmetallic wireway to more than 75 percent of its area at that point. + +### 378.58 Dead Ends. + +Dead ends of nonmetallic wireway shall be closed using listed fittings. + +### 378.60 Grounding. + +Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the nonmetallic wireway. A separate equipment grounding conductor shall not be required where the grounded conductor is used to ground equipment as permitted in 250.142. + +### 378.70 Extensions from Nonmetallic Wireways. + +Extensions from nonmetallic wireway shall be made with cord pendants or any wiring method of Chapter 3. A separate equipment grounding conductor shall be installed in, or an equipment grounding connection shall be made to, any of the wiring methods used for the extension. + +## Part III. Construction Specifications + +### 378.120 Marking. + +Nonmetallic wireways shall be marked so that the manufacturer’s name or trademark and interior cross-sectional area in square inches shall be visible after installation. Marking for limited smoke shall be permitted on the nonmetallic wireways that have limited smokeproducing characteristics. + +# Article 380 Multioutlet Assembly + +## Part I. General + +### 380.1 Scope. + +This article covers the use and installation requirements for multioutlet assemblies. + +> [!info] Informational Note: +> See the definition of multioutlet assembly in Article 100. + +## Part II. Installation + +### 380.10 Uses Permitted. + +The use of a multioutlet assembly shall be permitted in dry locations. + +### 380.12 Uses Not Permitted. + +A multioutlet assembly shall not be installed as follows: + +* (1) Where concealed, except that it shall be permissible to surround the back and sides of a metal multioutlet assembly by the building finish or recess a nonmetallic multioutlet assembly in a baseboard + +* (2) Where subject to severe physical damage + +* (3) Where the voltage is 300 volts or more between conductors unless the assembly is of metal having a thickness of not less than +1.02 mm (0.040 in.) + +* (4) Where subject to corrosive vapors + +* (5) In hoistways + +* (6) In any hazardous (classified) location, except as permitted by other articles in this Code + +* (7) Where cord and plug connected + +### 380.23 Insulated Conductors. + +For field-assembled multioutlet assemblies, insulated conductors shall comply with 380.23(A) and (B), as applicable. + +#### 380.23(A) Deflected Insulated Conductors. + +Where insulated conductors are deflected within a multioutlet assembly, either at the ends or where conduits, fittings, or other raceways or cables enter or leave the multioutlet assembly, or where the direction of the multioutlet assembly is deflected greater than +30 degrees, dimensions corresponding to one wire per terminal in Table 312.6(A) shall apply. + +#### 380.23(B) Multioutlet Assemblies Used as Pull Boxes. + +Where insulated conductors 4 AWG or larger are pulled through a multioutlet assembly, the distance between raceway and cable entries enclosing the same conductor shall not be less than that required by 314.28(A)(1) for straight pulls and 314.28(A)(2) for angle pulls. When transposing cable size into raceway size, the minimum metric designator (trade size) raceway required for the number and size of conductors in the cable shall be used. + +### 380.76 Metal Multioutlet Assembly Through Dry Partitions. + +It shall be permissible to extend a metal multioutlet assembly through (not run within) dry partitions if arrangements are made for removing the cap or cover on all exposed portions and no outlet is located within the partitions. + +# Article 382 Nonmetallic Extensions + +## Part I. General + +### 382.1 Scope. + +This article covers the use, installation, and construction specifications for nonmetallic extensions. + +### 382.2 Definitions. + +The definitions in this section shall apply within this article and throughout the Code. + +Concealable Nonmetallic Extension. + +A listed assembly of two, three, or four insulated circuit conductors within a nonmetallic jacket, an extruded thermoplastic covering, or a sealed nonmetallic covering. The classification includes surface extensions intended for mounting directly on the surface of walls or ceilings and concealed with paint, texture, joint compound, plaster, wallpaper, tile, wall paneling, or other similar materials. + +Nonmetallic Extension. + +An assembly of two insulated conductors within a nonmetallic jacket or an extruded thermoplastic covering. The classification includes surface extensions intended for mounting directly on the surface of walls or ceilings. + +### 382.6 Listing Requirements. + +Concealable nonmetallic extensions and associated fittings and devices shall be listed. The starting/source tap device for the extension shall contain and provide the following protection for all load-side extensions and devices: + +* (1) Supplementary overcurrent protection + +* (2) Level of protection equivalent to a Class A GFCI + +* (3) Level of protection equivalent to a portable GFCI + +* (4) Line and load-side miswire protection + +* (5) Provide protection from the effects of arc faults + +## Part II. Installation + +### 382.10 Uses Permitted. + +Nonmetallic extensions shall be permitted only in accordance with 382.10(A), (B), and (C). + +#### 382.10(A) From an Existing Outlet. + +The extension shall be from an existing outlet on a 15- or 20-ampere branch circuit. Where a concealable nonmetallic extension originates from a non–grounding-type receptacle, the installation shall comply with 250.130(C), 406.4(D)(2)(b), or 406.4(D)(2)(c). + +#### 382.10(B) Exposed and in a Dry Location. + +The extension shall be run exposed, or concealed as permitted in 382.15, and in a dry location. + +#### 382.10(C) Residential or Offices. + +For nonmetallic surface extensions mounted directly on the surface of walls or ceilings, the building shall be occupied for residential or office purposes and shall not exceed three floors abovegrade. Where identified for the use, concealable nonmetallic extensions shall be permitted more than three floors abovegrade. + +> [!info] Informational Note No. 1: +> See 310.14(A)(3) for temperature limitation of conductors. + +> [!info] Informational Note No. 2: +> See 362.10 for definition of First Floor. + +### 382.12 Uses Not Permitted. + +Nonmetallic extensions shall not be used as follows: + +* (1) In unfinished basements, attics, or roof spaces + +* (2) Where the voltage between conductors exceeds 150 volts for nonmetallic surface extensions and 300 volts for aerial cable + +* (3) Where subject to corrosive vapors + +* (4) Where run through a floor or partition, or outside the room in which it originates + +### 382.15 Exposed. + +#### 382.15(A) Nonmetallic Extensions. + +One or more extensions shall be permitted to be run in any direction from an existing outlet, but not on the floor or within 50 mm (2 in.) from the floor. + +#### 382.15(B) Concealable Nonmetallic Extensions. + +Where identified for the use, nonmetallic extensions shall be permitted to be concealed with paint, texture, concealing compound, plaster, wallpaper, tile, wall paneling, or other similar materials and installed in accordance with 382.15(A). + +### 382.26 Bends. + +#### 382.26(A) Nonmetallic Extensions. + +A bend that reduces the normal spacing between the conductors shall be covered with a cap to protect the assembly from physical damage. + +#### 382.26(B) Concealable Nonmetallic Extensions. + +Concealable extensions shall be permitted to be folded back over themselves and flattened as required for installation. + +### 382.30 Securing and Supporting. + +#### 382.30(A) Nonmetallic Extensions. + +Nonmetallic surface extensions shall be secured in place by approved means at intervals not exceeding 200 mm (8 in.), with an allowance for 300 mm (12 in.) to the first fastening where the connection to the supplying outlet is by means of an attachment plug. + +There shall be at least one fastening between each two adjacent outlets supplied. An extension shall be attached to only woodwork or plaster finish and shall not be in contact with any metal work or other conductive material other than with metal plates on receptacles. + +#### 382.30(B) Concealable Nonmetallic Extensions. + +All surface-mounted concealable nonmetallic extension components shall be firmly anchored to the wall or ceiling using an adhesive or mechanical anchoring system identified for this use. + +### 382.40 Boxes and Fittings. + +Each run shall terminate in a fitting, connector, or box that covers the end of the assembly. All fittings, connectors, and devices shall be of a type identified for the use. + +### 382.42 Devices. + +#### 382.42(A) Receptacles. + +All receptacles, receptacle housings, and self-contained devices used with concealable nonmetallic extensions shall be identified for this use. + +#### 382.42(B) Receptacles and Housings. + +Receptacle housings and self-contained devices designed either for surface or for recessed mounting shall be permitted for use with concealable nonmetallic extensions. Receptacle housings and self-contained devices shall incorporate means for facilitating entry and termination of concealable nonmetallic extensions and for electrically connecting the housing or device. Receptacle and self-contained devices shall comply with 406.4. Power and communications outlets installed together in common housing shall be permitted in accordance with 805.133(A)(1)(c), Exception No. 2. + +### 382.56 Splices and Taps. + +Extensions shall consist of a continuous unbroken length of the assembly, without splices, and without exposed conductors between fittings, connectors, or devices. Taps shall be permitted where approved fittings completely covering the tap connections are used. + +Aerial cable and its tap connectors shall be provided with an approved means for polarization. Receptacle-type tap connectors shall be of the locking type. + +## Part III. Construction Specifications (Concealable Nonmetallic Extensions Only) + +### 382.100 Construction. + +Concealable nonmetallic extensions shall be of a multilayer flat conductor design consisting of a center ungrounded conductor enclosed by a sectioned grounded conductor and an overall sectioned equipment grounding conductor. + +### 382.104 Flat Conductors. + +Concealable nonmetallic extensions shall be constructed, using flat copper conductors equivalent to 14 AWG or 12 AWG conductor sizes, and constructed per 382.104(A), (B), and (C). + +#### 382.104(A) Ungrounded Conductor (Center Layer). + +The ungrounded conductor shall consist of one or more ungrounded flat conductor(s) enclosed in accordance with 382.104(B) and (C) and identified in accordance with 310.6(C). + +#### 382.104(B) Grounded Conductor (Inner Sectioned Layers). + +The grounded conductor shall consist of two sectioned inner flat conductors that enclose the center ungrounded conductor(s). The sectioned grounded conductor shall be enclosed by the sectioned equipment grounding conductor and identified in accordance with +200.6. + +#### 382.104(C) Equipment Grounding Conductor (Outer Sectioned Layers). + +The equipment grounding conductor shall consist of two overall sectioned conductors that enclose the grounded conductor and ungrounded conductor(s) and shall comply with 250.4(A)(5). The equipment grounding conductor layers shall be identified by any one of the following methods: + +* (1) As permitted in 250.119 + +* (2) A clear covering + +* (3) One or more continuous green stripes or hash marks + +* (4) The term “Equipment Grounding Conductor” printed at regular intervals throughout the cable + +### 382.112 Insulation. + +The ungrounded and grounded flat conductor layers shall be individually insulated and comply with 310.14(A)(3). The equipment grounding conductor shall be covered or insulated. + +### 382.120 Marking. + +#### 382.120(A) Cable. + +Concealable nonmetallic extensions shall be clearly and durably marked on both sides at intervals of not more than 610 mm (24 in.) with the information required by 310.8(A) and with the following additional information: + +* (1) Material of conductors + +* (2) Maximum temperature rating + +* (3) Ampacity + +#### 382.120(B) Conductor Identification. + +Conductors shall be clearly and durably identified on both sides throughout their length as specified in 382.104. + +# Article 384 Strut-Type Channel Raceway + +## Part I. General + +### 384.1 Scope. + +This article covers the use, installation, and construction specifications of strut-type channel raceway. + +### 384.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Strut-Type Channel Raceway. + +A metal raceway that is intended to be mounted to the surface of or suspended from a structure, with associated accessories for the installation of electrical conductors and cables. + +### 384.6 Listing Requirements. + +Strut-type channel raceways and accessories shall be listed and identified for such use. + +## Part II. Installation + +### 384.10 Uses Permitted. + +The use of strut-type channel raceways shall be permitted in the following: + +* (1) Where exposed. + +* (2) In dry locations. + +* (3) In locations subject to corrosive vapors where protected by finishes approved for the condition. + +* (4) As power poles. + +* (5) In hazardous (classified) locations as permitted in Chapter 5. + +* (6) As extensions of unbroken lengths through walls, partitions, and floors where closure strips are removable from either side and the portion within the wall, partition, or floor remains covered. + +* (7) Ferrous channel raceways and fittings protected from corrosion solely by enamel shall be permitted only indoors. + +### 384.12 Uses Not Permitted. + +Strut-type channel raceways shall not be used as follows: + +* (1) Where concealed. + +* (2) Ferrous channel raceways and fittings protected from corrosion solely by enamel shall not be permitted where subject to severe corrosive influences. + +### 384.21 Size of Conductors. + +No conductor larger than that for which the raceway is listed shall be installed in strut-type channel raceways. + +### 384.22 Number of Conductors. + +The number of conductors or cables permitted in strut-type channel raceways shall not exceed the percentage fill using Table 384.22 and applicable cross-sectional area of specific types and sizes of wire given in the tables in Chapter 9. + +The adjustment factors of 310.15(C)(1) shall not apply to conductors installed in strut-type channel raceways where all of the following conditions are met: + +* (1) The cross-sectional area of the raceway exceeds 2500 mm (4 in. ). + +* (2) The current-carrying conductors do not exceed 30 in number. + +* (3) The sum of the cross-sectional areas of all contained conductors does not exceed 20 percent of the interior cross-sectional area of the strut-type channel raceways. + +Table 384.22 Channel Size and Inside CrossSectional + +Area + +Size + +Channel + +Area 40% Area 25% Area in. mm in. mm in. mm +15⁄8 × 15⁄16 0.887 572 0.355 229 0.222 143 +15⁄8 × 1 1.151 743 0.460 297 0.288 186 +15⁄8 × 13⁄8 1.677 1076 0.671 433 0.419 270 +15⁄8 × 15⁄8 2.028 1308 0.811 523 0.507 327 +15⁄8 × 27⁄16 3.169 2045 1.267 817 0.792 511 +15⁄8 × 31⁄4 4.308 2780 1.723 1112 1.077 695 +11⁄2 × 3⁄4 0.849 548 0.340 219 0.212 137 +11⁄2 × 11⁄2 1.828 1179 0.731 472 0.457 295 +11⁄2 × 17⁄8 2.301 1485 0.920 594 0.575 371 +11⁄2 × 3 3.854 2487 1.542 995 0.964 622 + +Raceways with external joiners shall use a 40 percent wire fill calculation to determine the number of conductors permitted. + +Raceways with internal joiners shall use a 25 percent wire fill calculation to determine the number of conductors permitted. + +### 384.30 Securing and Supporting. + +#### 384.30(A) Surface Mount. + +2 2 +* † +2 2 2 2 2 2 +* +† + +A surface mount strut-type channel raceway shall be secured to the mounting surface with retention straps external to the channel at intervals not exceeding 3 m (10 ft) and within 900 mm (3 ft) of each outlet box, cabinet, junction box, or other channel raceway termination. + +#### 384.30(B) Suspension Mount. + +Strut-type channel raceways shall be permitted to be suspension mounted in air with identified methods at intervals not to exceed 3 m +(10 ft) and within 900 mm (3 ft) of channel raceway terminations and ends. + +### 384.56 Splices and Taps. + +Splices and taps shall be permitted in raceways that are accessible after installation by having a removable cover. The conductors, including splices and taps, shall not fill the raceway to more than 75 percent of its area at that point. All splices and taps shall be made by approved methods. + +### 384.60 Grounding. + +Strut-type channel raceway enclosures providing a transition to or from other wiring methods shall have a means for connecting an equipment grounding conductor. Strut-type channel raceways shall be permitted as an equipment grounding conductor in accordance with 250.118(13). Where a snap-fit metal cover for strut-type channel raceways is used to achieve electrical continuity in accordance with the listing, this cover shall not be permitted as the means for providing electrical continuity for a receptacle mounted in the cover. + +## Part III. Construction Specifications + +### 384.100 Construction. + +Strut-type channel raceways and their accessories shall be of a construction that distinguishes them from other raceways. Raceways and their elbows, couplings, and other fittings shall be designed such that the sections can be electrically and mechanically coupled together and installed without subjecting the wires to abrasion. They shall comply with 384.100(A), (B), and (C). + +#### 384.100(A) Material. + +Raceways and accessories shall be formed of steel, stainless steel, or aluminum. + +#### 384.100(B) Corrosion Protection. + +Steel raceways and accessories shall be protected against corrosion by galvanizing or by an organic coating. + +> [!info] Informational Note: +> Enamel and PVC coatings are examples of organic coatings that provide corrosion protection. + +#### 384.100(C) Cover. + +Covers of strut-type channel raceways shall be either metal or nonmetallic. + +### 384.120 Marking. + +Each length of strut-type channel raceway shall be clearly and durably identified as required in the first sentence of 110.21(A). + +# Article 386 Surface Metal Raceways + +## Part I. General + +### 386.1 Scope. + +This article covers the use, installation, and construction specifications for surface metal raceways and associated fittings. + +### 386.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Surface Metal Raceway. + +A metal raceway that is intended to be mounted to the surface of a structure, with associated couplings, connectors, boxes, and fittings for the installation of electrical conductors. + +### 386.6 Listing Requirements. + +Surface metal raceway and associated fittings shall be listed. + +## Part II. Installation + +### 386.10 Uses Permitted. + +The use of surface metal raceways shall be permitted in the following: + +* (1) In dry locations. + +* (2) In Class I, Division 2 hazardous (classified) locations as permitted in 501.10(B)(3). + +* (3) Under raised floors, as permitted in 645.5(E)(2). + +* (4) Extension through walls and floors. Surface metal raceway shall be permitted to pass transversely through dry walls, dry partitions, and dry floors if the length passing through is unbroken. Access to the conductors shall be maintained on both sides of the wall, partition, or floor. + +### 386.12 Uses Not Permitted. + +Surface metal raceways shall not be used in the following: + +* (1) Where subject to severe physical damage, unless otherwise approved + +* (2) Where the voltage is 300 volts or more between conductors, unless the metal has a thickness of not less than 1.02 mm +(0.040 in.) nominal + +* (3) Where subject to corrosive vapors + +* (4) In hoistways + +* (5) Where concealed, except as permitted in 386.10 + +### 386.21 Size of Conductors. + +No conductor larger than that for which the raceway is designed shall be installed in surface metal raceway. + +### 386.22 Number of Conductors or Cables. + +The number of conductors or cables installed in surface metal raceway shall not be greater than the number for which the raceway is designed. Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. + +The adjustment factors of 310.15(C)(1) shall not apply to conductors installed in surface metal raceways where all of the following conditions are met: + +* (1) The cross-sectional area of the raceway exceeds 2500 mm (4 in. ). + +* (2) The current-carrying conductors do not exceed 30 in number. + +* (3) The sum of the cross-sectional areas of all contained conductors does not exceed 20 percent of the interior cross-sectional area of the surface metal raceway. + +### 386.30 Securing and Supporting. + +Surface metal raceways and associated fittings shall be supported in accordance with the manufacturer's installation instructions. + +### 386.56 Splices and Taps. + +Splices and taps shall be permitted in surface metal raceways having a removable cover that is accessible after installation. The conductors, including splices and taps, shall not fill the raceway to more than 75 percent of its area at that point. Splices and taps in surface metal raceways without removable covers shall be made only in boxes. All splices and taps shall be made by approved methods. + +Taps of Type FC cable installed in surface metal raceway shall be made in accordance with 322.56(B). + +### 386.60 Grounding. + +Surface metal raceway enclosures providing a transition from other wiring methods shall have a means for connecting an equipment grounding conductor. + +### 386.70 Combination Raceways. + +When combination surface metal raceways are used for both signaling and for lighting and power circuits, the different systems shall be run in separate compartments identified by stamping, imprinting, or color coding of the interior finish. + +## Part III. Construction Specifications + +### 386.100 Construction. + +Surface metal raceways shall be of such construction as will distinguish them from other raceways. Surface metal raceways and their elbows, couplings, and similar fittings shall be designed so that the sections can be electrically and mechanically coupled together and installed without subjecting the wires to abrasion. + +Where covers and accessories of nonmetallic materials are used on surface metal raceways, they shall be identified for such use. + +### 386.120 Marking. + +2 2 + +Each length of surface metal raceway shall be clearly and durably identified as required in the first sentence of 110.21(A). + +# Article 388 Surface Nonmetallic Raceways + +## Part I. General + +### 388.1 Scope. + +This article covers the use, installation, and construction specifications for surface nonmetallic raceways and associated fittings. + +### 388.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Surface Nonmetallic Raceway. + +A nonmetallic raceway that is intended to be mounted to the surface of a structure, with associated couplings, connectors, boxes, and fittings for the installation of electrical conductors. + +### 388.6 Listing Requirements. + +Surface nonmetallic raceway and associated fittings shall be listed. + +## Part II. Installation + +### 388.10 Uses Permitted. + +Surface nonmetallic raceways shall be permitted as follows: + +* (1) The use of surface nonmetallic raceways shall be permitted in dry locations. + +* (2) Extension through walls and floors shall be permitted. Surface nonmetallic raceway shall be permitted to pass transversely through dry walls, dry partitions, and dry floors if the length passing through is unbroken. Access to the conductors shall be maintained on both sides of the wall, partition, or floor. + +### 388.12 Uses Not Permitted. + +Surface nonmetallic raceways shall not be used in the following: + +* (1) Where concealed, except as permitted in 388.10(2) + +* (2) Where subject to severe physical damage + +* (3) Where the voltage is 300 volts or more between conductors, unless listed for higher voltage + +* (4) In hoistways + +* (5) In any hazardous (classified) location, except as permitted by other articles in this Code + +* (6) Where subject to ambient temperatures exceeding those for which the nonmetallic raceway is listed + +* (7) For conductors whose insulation temperature limitations would exceed those for which the nonmetallic raceway is listed + +### 388.21 Size of Conductors. + +No conductor larger than that for which the raceway is designed shall be installed in surface nonmetallic raceway. + +### 388.22 Number of Conductors or Cables. + +The number of conductors or cables installed in surface nonmetallic raceway shall not be greater than the number for which the raceway is designed. Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. + +### 388.30 Securing and Supporting. + +Surface nonmetallic raceways and associated fittings shall be supported in accordance with the manufacturer's installation instructions. + +### 388.56 Splices and Taps. + +Splices and taps shall be permitted in surface nonmetallic raceways having a cover capable of being opened in place that is accessible after installation. The conductors, including splices and taps, shall not fill the raceway to more than 75 percent of its area at that point. + +Splices and taps in surface nonmetallic raceways without covers capable of being opened in place shall be made only in boxes. All splices and taps shall be made by approved methods. + +### 388.60 Grounding. + +Where equipment grounding is required, a separate equipment grounding conductor shall be installed in the raceway. + +### 388.70 Combination Raceways. + +When combination surface nonmetallic raceways are used both for signaling and for lighting and power circuits, the different systems shall be run in separate compartments identified by stamping, imprinting, or color coding of the interior finish. + +## Part III. Construction Specifications + +### 388.100 Construction. + +Surface nonmetallic raceways shall be of such construction as will distinguish them from other raceways. Surface nonmetallic raceways and their elbows, couplings, and similar fittings shall be designed so that the sections can be mechanically coupled together and installed without subjecting the wires to abrasion. + +Surface nonmetallic raceways and fittings are made of suitable nonmetallic material that is resistant to moisture and chemical atmospheres. It shall also be flame retardant, resistant to impact and crushing, resistant to distortion from heat under conditions likely to be encountered in service, and resistant to low-temperature effects. + +### 388.120 Marking. + +Surface nonmetallic raceways that have limited smoke-producing characteristics shall be permitted to be so identified. Each length of surface nonmetallic raceway shall be clearly and durably identified as required in the first sentence of 110.21(A). + +# Article 390 Underfloor Raceways + +## Part I. General + +### 390.1 Scope. + +This article covers the use and installation requirements for underfloor raceways. + +### 390.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Underfloor Raceway. + +A raceway and associated components designed and intended for installation beneath or flush with the surface of a floor for the installation of cables and electrical conductors. + +## Part II. Installation + +### 390.10 Uses Permitted. + +The installation of underfloor raceways shall be permitted beneath the surface of concrete or other flooring material or in office occupancies where laid flush with the concrete floor and covered with linoleum or equivalent floor covering. + +### 390.12 Uses Not Permitted. + +Underfloor raceways shall not be installed (1) where subject to corrosive vapors or (2) in any hazardous (classified) locations, except as permitted by 504.20 and in Class I, Division 2 locations as permitted in 501.10(B) (3). Unless made of a material approved for the condition or unless corrosion protection approved for the condition is provided, metal underfloor raceways, junction boxes, and fittings shall not be installed in concrete or in areas subject to severe corrosive influences. + +### 390.15 Covering. + +Raceway coverings shall comply with 390.15(A) through (D). + +#### 390.15(A) Raceways Not over 100 mm (4 in.) Wide. + +Half-round and flat-top raceways not over 100 mm (4 in.) in width shall have not less than 20 mm (3⁄4 in.) of concrete or wood above the raceway. + +> [!important] Exception: +> As permitted in 390.15(C) and (D) for flat-top raceways. + +#### 390.15(B) Raceways over 100 mm (4 in.) Wide But Not over 200 mm (8 in.) Wide. + +Flat-top raceways over 100 mm (4 in.) but not over 200 mm (8 in.) wide with a minimum of 25 mm (1 in.) spacing between raceways shall be covered with concrete to a depth of not less than 25 mm (1 in.). Raceways spaced less than 25 mm (1 in.) apart shall be covered with concrete to a depth of 38 mm (11⁄2 in.). + +#### 390.15(C) Trench-Type Raceways Flush with Concrete. + +Trench-type flush raceways with removable covers shall be permitted to be laid flush with the floor surface. Such approved raceways shall be designed so that the cover plates provide adequate mechanical protection and rigidity equivalent to junction box covers. + +#### 390.15(D) Other Raceways Flush with Concrete. + +In office occupancies, approved metal flat-top raceways, if not over 100 mm (4 in.) in width, shall be permitted to be laid flush with the concrete floor surface, provided they are covered with substantial linoleum that is not less than 1.6 mm (1⁄16 in.) thick or with equivalent floor covering. Where more than one and not more than three single raceways are each installed flush with the concrete, they shall be contiguous with each other and joined to form a rigid assembly. + +### 390.20 Size of Conductors. + +No conductor larger than that for which the raceway is designed shall be installed in underfloor raceways. + +### 390.22 Maximum Number of Conductors in Raceway. + +The combined cross-sectional area of all conductors or cables shall not exceed 40 percent of the interior cross-sectional area of the raceway. + +### 390.23 Ampacity of Conductors. + +The ampacity adjustment factors in 310.15(C) shall apply to conductors installed in underfloor raceways. + +### 390.56 Splices and Taps. + +Splices and taps shall be made only in junction boxes. + +For the purposes of this section, so-called loop wiring (continuous, unbroken conductor connecting the individual outlets) shall not be considered to be a splice or tap. + +> [!important] Exception: +> Splices and taps shall be permitted in trench-type flush raceway having a removable cover that is accessible after installation. The conductors, including splices and taps, shall not fill more than 75 percent of the raceway area at that point. + +### 390.57 Discontinued Outlets. + +When an outlet is abandoned, discontinued, or removed, the sections of circuit conductors supplying the outlet shall be removed from the raceway. No splices or reinsulated conductors, such as would be the case with abandoned outlets on loop wiring, shall be allowed in raceways. + +### 390.70 Laid in Straight Lines. + +Underfloor raceways shall be laid so that a straight line from the center of one junction box to the center of the next junction box coincides with the centerline of the raceway system. Raceways shall be firmly held in place to prevent disturbing this alignment during construction. + +### 390.71 Markers at Ends. + +A suitable marker shall be installed at or near each end of each straight run of raceways to locate the last insert. + +### 390.73 Dead Ends. + +Dead ends of raceways shall be closed. + +### 390.74 Junction Boxes. + +Junction boxes shall be leveled to the floor grade and sealed to prevent the free entrance of water or concrete. Junction boxes used with metal raceways shall be metal and shall be electrically continuous with the raceways. + +### 390.75 Inserts. + +Inserts shall be leveled and sealed to prevent the entrance of concrete. Inserts used with metal raceways shall be metal and shall be electrically continuous with the raceway. Inserts set in or on fiber raceways before the floor is laid shall be mechanically secured to the raceway. Inserts set in fiber raceways after the floor is laid shall be screwed into the raceway. When cutting through the raceway wall and setting inserts, chips and other dirt shall not be allowed to remain in the raceway, and tools shall be used that are designed so as to prevent the tool from entering the raceway and damaging conductors that may be in place. + +### 390.76 Connections to Cabinets and Wall Outlets. + +Connections from underfloor raceways to distribution centers and wall outlets shall be made by approved fittings or by any of the wiring methods in Chapter 3, where installed in accordance with the respective articles. + +# Article 392 Cable Trays + +## Part I. General + +### 392.1 Scope. + +This article covers cable tray systems, including ladder, ventilated trough, ventilated channel, solid bottom, and other similar structures. + +> [!info] Informational Note: +> For further information on cable trays, see ANSI/NEMA–VE 1-2017, Metal Cable Tray Systems, and NECA/NEMA +105-2015, Standard for Installing Metal Cable Tray Systems. + +### 392.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Cable Tray System. + +A unit or assembly of units or sections and associated fittings forming a structural system used to securely fasten or support cables and raceways. + +## Part II. Installation + +### 392.10 Uses Permitted. + +Cable tray shall be permitted to be used as a support system for wiring methods containing service conductors, feeders, branch circuits, communications circuits, control circuits, and signaling circuits. Single insulated conductors shall be permitted in cable tray only when installed in accordance with 392.10(B)(1). Cable tray installations shall not be limited to industrial establishments. Where exposed to direct rays of the sun, insulated conductors and jacketed cables shall be identified as being sunlight resistant. Cable trays and their associated fittings shall be identified for the intended use. + +#### 392.10(A) Wiring Methods. + +The wiring methods in Table 392.10(A) shall be permitted to be installed in cable tray systems under the conditions described in their respective articles and sections. + +Table 392.10(A) Wiring Methods + +Wiring Method Article + +Armored cable: Type AC 320 + +CATV cables 820 + +Class 2 and Class 3 cables 725 + +Communications cables 800 + +Communications raceways 725, 770, and +800 + +Electrical metallic tubing: Type EMT 358 + +Electrical nonmetallic tubing: Type ENT 362 + +Fire alarm cables 760 + +Flexible metal conduit: Type FMC 348 + +Flexible metallic tubing: Type FMT 360 + +Instrumentation tray cable: Type ITC 727 + +Intermediate metal conduit: Type IMC 342 + +Liquidtight flexible metal conduit: Type LFMC 350 + +Liquidtight flexible nonmetallic conduit: Type LFNC 356 + +Metal-clad cable: Type MC 330 + +Mineral-insulated, metal-sheathed cable: Type MI 332 + +Network-powered broadband communications cables 830 + +Nonmetallic-sheathed cable: Types NM, NMC, and NMS 334 + +Non–power-limited fire alarm cable 760 + +Optical fiber cables 770 + +Other factory-assembled, multiconductor control, signal, or power cables that are specifically approved for installation in cable trays + +Power and control tray cable: Type TC 336 + +Power-limited fire alarm cable 760 + +Wiring Method Article + +Power-limited tray cable 725 + +Rigid metal conduit: Type RMC 344 + +Rigid polyvinyl chloride conduit: Type PVC 352 + +Reinforced thermosetting resin conduit: Type RTRC 355 + +Service-entrance cable: Types SE and USE 338 + +Underground feeder and branch-circuit cable: Type UF 340 + +#### 392.10(B) In Industrial Establishments. + +The wiring methods in Table 392.10(A) shall be permitted to be used in any industrial establishment under the conditions described in their respective articles. In industrial establishments only, where conditions of maintenance and supervision ensure that only qualified persons service the installed cable tray system, any of the cables in 392.10(B)(1) and (B)(2) shall be permitted to be installed in ladder, ventilated trough, solid bottom, or ventilated channel cable trays. + +##### 392.10(B)(1) Single-Conductor Cables. + +Single-conductor cables shall be permitted to be installed in accordance with (B)(1)(a) through (B)(1)(c). + +* (a) Single-conductor cables shall be 1/0 AWG or larger and shall be of a type listed and marked on the surface for use in cable trays. Where 1/0 AWG through 4/0 AWG single-conductor cables are installed in ladder cable tray, the maximum allowable rung spacing for the ladder cable tray shall be 225 mm (9 in.). + +* (b) Welding cables shall comply with Article 630, Part IV. + +* (c) Single conductors used as equipment grounding conductors shall be insulated, covered, or bare, and they shall be 4 AWG or larger. + +##### 392.10(B)(2) Single- and Multiconductor Medium Voltage Cables. + +Single- and multiconductor medium voltage cables shall be Type MV cable. Single conductors shall be installed in accordance with +392.10(B)(1). + +#### 392.10(C) Hazardous (Classified) Locations. + +Cable trays in hazardous (classified) locations shall contain only the cable types and raceways permitted by other articles in this Code. + +#### 392.10(D) Nonmetallic Cable Tray. + +In addition to the uses permitted elsewhere in 392.10, nonmetallic cable tray shall be permitted in corrosive areas and in areas requiring voltage isolation. + +#### 392.10(E) Airfield Lighting Cable Tray. + +In airports where maintenance and supervision conditions ensure that only qualified persons can access, install, or service the cable, airfield lighting cable used in series circuits that are rated up to 5000 volts and are powered by constant current regulators shall be permitted to be installed in cable trays. + +> [!info] Informational Note: +> Federal Aviation Administration (FAA) Advisory Circulars (ACs) provide additional practices and methods for airport lighting. + +### 392.12 Uses Not Permitted. + +Cable tray systems shall not be used in hoistways or where subject to severe physical damage. + +### 392.18 Cable Tray Installation. + +#### 392.18(A) Complete System. + +Cable trays shall be installed as a complete system. Field bends or modifications shall be so made that the electrical continuity of the cable tray system and support for the cables is maintained. Cable tray systems shall be permitted to have mechanically discontinuous segments between cable tray runs or between cable tray runs and equipment. + +#### 392.18(B) Completed Before Installation. + +Each run of cable tray shall be completed before the installation of cables. + +#### 392.18(C) Covers. + +In portions of runs where additional protection is required, covers or enclosures providing the required protection shall be of a material that is compatible with the cable tray. + +#### 392.18(D) Through Partitions and Walls. + +Cable trays shall be permitted to extend transversely through partitions and walls or vertically through platforms and floors in wet or dry locations where the installations, complete with installed cables, are made in accordance with the requirements of 300.21. + +#### 392.18(E) Exposed and Accessible. + +Cable trays shall be exposed and accessible, except as permitted by 392.18(D). + +#### 392.18(F) Adequate Access. + +Sufficient space shall be provided and maintained about cable trays to permit adequate access for installing and maintaining the cables. + +#### 392.18(G) Raceways, Cables, Boxes, and Conduit Bodies Supported from Cable Tray Systems. + +In industrial facilities where conditions of maintenance and supervision ensure that only qualified persons service the installation and where the cable tray systems are designed and installed to support the load, such systems shall be permitted to support raceways and cables, and boxes and conduit bodies covered in 314.1. For raceways terminating at the tray, a listed cable tray clamp or adapter shall be used to securely fasten the raceway to the cable tray system. Additional supporting and securing of the raceway shall be in accordance with the requirements of the appropriate raceway article. For raceways or cables running parallel to and attached to the bottom or side of a cable tray system, fastening and supporting shall be in accordance with the requirements of the appropriate raceway or cable article. + +For boxes and conduit bodies attached to the bottom or side of a cable tray system, fastening and supporting shall be in accordance with the requirements of 314.23. + +#### 392.18(H) Marking. + +Cable trays containing conductors operating over 600 volts shall have a permanent, legible warning notice carrying the wording +“DANGER — HIGH VOLTAGE — KEEP AWAY” placed in a readily visible position on all cable trays, with the spacing of warning notices not to exceed 3 m (10 ft). The danger marking(s) or labels shall comply with 110.21(B). + +> [!important] Exception: +> Where not accessible (as applied to equipment), in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation, cable tray system warning notices shall be located where necessary for the installation to ensure safe maintenance and operation. + +### 392.20 Cable and Conductor Installation. + +#### 392.20(A) Multiconductor Cables Operating at 1000 Volts or Less. + +Multiconductor cables operating at 1000 volts or less shall be permitted to be installed in the same tray. +392.20(B) Cables Operating at Over 1000 Volts. + +Cables operating at over 1000 volts and those operating at 1000 volts or less installed in the same cable tray shall comply with either of the following: + +* (1) The cables operating at over 1000 volts are Type MC. + +* (2) The cables operating at over 1000 volts are separated from the cables operating at 1000 volts or less by a solid fixed barrier of a material compatible with the cable tray. + +#### 392.20(C) Connected in Parallel. + +Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(G), the conductors shall be installed in groups consisting of not more than one conductor per phase, neutral, or grounded conductor to prevent current imbalance in the paralleled conductors due to inductive reactance. + +Single conductors shall be securely bound in circuit groups to prevent excessive movement due to fault-current magnetic forces unless single conductors are cabled together, such as triplexed assemblies. + +#### 392.20(D) Single Conductors. + +Where any of the single conductors installed in ladder or ventilated trough cable trays are 1/0 through 4/0 AWG, all single conductors shall be installed in a single layer. Conductors that are bound together to comprise each circuit group shall be permitted to be installed in other than a single layer. + +### 392.22 Number of Conductors or Cables. + +#### 392.22(A) Number of Multiconductor Cables, Rated 2000 Volts or Less, in Cable Trays. + +The number of multiconductor cables, rated 2000 volts or less, permitted in a single cable tray shall not exceed the requirements of this section. The conductor sizes shall apply to both aluminum and copper conductors. Where dividers are used, fill calculations shall apply to each divided section of the cable tray. + +##### 392.22(A)(1) Ladder or Ventilated Trough Cable Trays Containing Any Mixture of Cables. + +Where ladder or ventilated trough cable trays contain multiconductor power or lighting cables, or any mixture of multiconductor power, lighting, control, and signal cables, the maximum number of cables shall conform to the following: + +* (a) Where all of the cables are 4/0 AWG or larger, the sum of the diameters of all cables shall not exceed the cable tray width, and the cables shall be installed in a single layer. Where the cable ampacity is determined according to 392.80(A)(1)(c), the cable tray width shall not be less than the sum of the diameters of the cables and the sum of the required spacing widths between the cables. + +* (b) Where all of the cables are smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables shall not exceed the maximum allowable cable fill area in Column 1 of Table 392.22(A) for the appropriate cable tray width. + +* (c) Where 4/0 AWG or larger cables are installed in the same cable tray with cables smaller than 4/0 AWG, the sum of the crosssectional areas of all cables smaller than 4/0 AWG shall not exceed the maximum allowable fill area resulting from the calculation in Column 2 of Table 392.22(A) for the appropriate cable tray width. The 4/0 AWG and larger cables shall be installed in a single layer, and no other cables shall be placed on them. + +Table 392.22(A) Allowable Cable Fill Area for Multiconductor Cables in Ladder, Ventilated Trough, or + +Solid Bottom Cable Trays for Cables Rated 2000 Volts or Less + +Inside Width of Cable Tray + +Maximum Allowable Fill Area for Multiconductor Cables + +Ladder or Ventilated Trough or Wire + +Mesh Cable Trays, 392.22(A)(1) + +Solid Bottom Cable Trays, +392.22(A)(3) + +Column 1 + +Applicable for +392.22(A)(1)(b) + +Only + +Column 2 + +Applicable for 392.22(A) +(1)(c) Only + +Column 3 Applicable for 392.22(A)(3)(b) Only + +Column 4 + +Applicable for +392.22(A)(3)(c) + +Only mm in. mm in. mm in. mm in. mm in. +50 2.0 1,500 2.5 1,500 – (30 Sd) 2.5 – (1.2 Sd) 1,200 2.0 1,200 – (25 + +Sd) +2.0 – + +Sd +100 4.0 3,000 4.5 3,000 – (30 Sd) 4.5 – (1.2 Sd) 2,300 3.5 2,300 – (25 + +Sd) +3.5 – + +Sd +150 6.0 4,500 7.0 4,500 – (30 Sd) 7 – (1.2 Sd) 3,500 5.5 3,500 – (25 + +Sd) +5.5– + +Sd +200 8.0 6,000 9.5 6,000 – (30 Sd) 9.5 – (1.2 Sd) 4,500 7.0 4,500 – (25 + +Sd) +7.0 – + +Sd +225 9.0 6,800 10.5 6,800 – (30 Sd) 10.5 – (1.2 Sd) 5,100 8.0 5,100 – (25 + +Sd) +8.0 – + +Sd +300 12.0 9,000 14.0 9,000 – (30 Sd) 14 – (1.2 Sd) 7,100 11.0 7,100 – (25 + +Sd) +11.0 – + +Sd +400 16.0 12,000 18.5 12,000 – (30 Sd) 18.5 – (1.2 Sd) 9,400 14.5 9,400 – (25 + +Sd) +14.5 – + +Sd +450 18.0 13,500 21.0 13,500 – (30 Sd) 21 – (1.2 Sd) 10,600 16.5 10,600 – +(25 Sd) +16.5 – + +Sd +500 20.0 15,000 23.5 15,000 – (30 Sd) 23.5 – (1.2 Sd) 11,800 18.5 11,800 – +(25 Sd) +18.5 – + +Sd +600 24.0 18,000 28.0 18,000 – (30 Sd) 28 – (1.2 Sd) 14,200 22.0 14,200 – +(25 Sd) +22.0 – + +Sd +750 30.0 22,500 35.0 22,500 – (30 Sd) 35 – (1.2 Sd) 17,700 27.5 17,700 – +(25 Sd) +27.5 – + +Sd +900 36.0 27,000 42.0 27,000 – (30 Sd) 42 – (1.2 Sd) 21,300 33.0 21,300 – +(25 Sd) +33.0 – + +Sd a a +2 2 2 2 2 2 2 2 b b b b b b b b + +The maximum allowable fill areas in Columns 2 and 4 shall be calculated. For example, the maximum allowable fill in mm for a 150mm wide cable tray in Column 2 shall be 4500 minus (30 multiplied by Sd) \[the maximum allowable fill, in square inches, for a 6-in. wide cable tray in Column 2 shall be 7 minus (1.2 multiplied by Sd)\]. + +The term Sd in Columns 2 and 4 is equal to the sum of the diameters, in mm, of all cables 107.2 mm (in inches, of all 4/0 AWG) and larger multiconductor cables in the same cable tray with smaller cables. +392.22(A)(2) Ladder or Ventilated Trough Cable Trays Containing Multiconductor Control and/or Signal + +Cables Only. + +Where a ladder or ventilated trough cable tray having a usable inside depth of 150 mm (6 in.) or less contains multiconductor control and/or signal cables only, the sum of the cross-sectional areas of all cables at any cross section shall not exceed 50 percent of the interior cross-sectional area of the cable tray. A depth of 150 mm (6 in.) shall be used to calculate the allowable interior cross-sectional area of any cable tray that has a usable inside depth of more than 150 mm (6 in.). + +##### 392.22(A)(3) Solid Bottom Cable Trays Containing Any Mixture of Cables. + +Where solid bottom cable trays contain multiconductor power or lighting cables, or any mixture of multiconductor power, lighting, control, and signal cables, the maximum number of cables shall conform to the following: + +* (a) Where all of the cables are 4/0 AWG or larger, the sum of the diameters of all cables shall not exceed 90 percent of the cable tray width, and the cables shall be installed in a single layer. + +* (b) Where all of the cables are smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables shall not exceed the maximum allowable cable fill area in Column 3 of Table 392.22(A) for the appropriate cable tray width. + +* (c) Where 4/0 AWG or larger cables are installed in the same cable tray with cables smaller than 4/0 AWG, the sum of the crosssectional areas of all cables smaller than 4/0 AWG shall not exceed the maximum allowable fill area resulting from the computation in Column 4 of Table 392.22(A) for the appropriate cable tray width. The 4/0 AWG and larger cables shall be installed in a single layer, and no other cables shall be placed on them. + +##### 392.22(A)(4) Solid Bottom Cable Tray Containing Multiconductor Control and/or Signal Cables Only. + +Where a solid bottom cable tray having a usable inside depth of 150 mm (6 in.) or less contains multiconductor control and/or signal cables only, the sum of the cross sectional areas of all cables at any cross section shall not exceed 40 percent of the interior crosssectional area of the cable tray. A depth of 150 mm (6 in.) shall be used to calculate the allowable interior cross-sectional area of any cable tray that has a usable inside depth of more than 150 mm (6 in.). + +##### 392.22(A)(5) Ventilated Channel Cable Trays Containing Multiconductor Cables of Any Type. + +Where ventilated channel cable trays contain multiconductor cables of any type, the following shall apply: + +* (a) Where only one multiconductor cable is installed, the cross-sectional area shall not exceed the value specified in Column 1 of + +Table 392.22(A)(5). + +* (b) Where more than one multiconductor cable is installed, the sum of the cross-sectional area of all cables shall not exceed the value specified in Column 2 of Table 392.22(A) (5). + +Table 392.22(A)(5) Allowable Cable Fill Area for Multiconductor Cables in Ventilated + +Channel Cable Trays for Cables Rated 2000 Volts or Less + +Inside Width of Cable Tray + +Maximum Allowable Fill Area for Multiconductor Cables + +Column 1 + +One Cable + +Column 2 + +More Than + +One Cable mm in. mm in. mm in. +75 3 1500 2.3 850 1.3 +100 4 2900 4.5 1600 2.5 +150 6 4500 7.0 2450 3.8 + +##### 392.22(A)(6) Solid Channel Cable Trays Containing Multiconductor Cables of Any Type. + +Where solid channel cable trays contain multiconductor cables of any type, the following shall apply: + +* (a) Where only one multiconductor cable is installed, the cross-sectional area of the cable shall not exceed the value specified in + +Column 1 of Table 392.22(A)(6). + +* (b) Where more than one multiconductor cable is installed, the sum of the cross-sectional area of all cable shall not exceed the a 2 b +2 2 2 2 value specified in Column 2 of Table 392.22(A)(6). + +Table 392.22(A)(6) Allowable Cable Fill Area for Multiconductor Cables in + +Solid Channel Cable Trays for Cables Rated 2000 Volts or Less + +Inside Width of Cable Tray + +Column 1 + +One Cable Column 2 More Than One Cable mm in. mm in. mm in. +50 2 850 1.3 500 0.8 +75 3 1300 2.0 700 1.1 +100 4 2400 3.7 1400 2.1 +150 6 3600 5.5 2100 3.2 + +#### 392.22(B) Number of Single-Conductor Cables, Rated 2000 Volts or Less, in Cable Trays. + +The number of single conductor cables, rated 2000 volts or less, permitted in a single cable tray section shall not exceed the requirements of this section. The single conductors, or conductor assemblies, shall be evenly distributed across the cable tray. The conductor sizes shall apply to both aluminum and copper conductors. + +##### 392.22(B)(1) Ladder or Ventilated Trough Cable Trays. + +Where ladder or ventilated trough cable trays contain single-conductor cables, the maximum number of single conductors shall conform to the following: + +* (a) Where all of the cables are 1000 kcmil or larger, the sum of the diameters of all single-conductor cables shall not exceed the cable tray width, and the cables shall be installed in a single layer. Conductors that are bound together to comprise each circuit group shall be permitted to be installed in other than a single layer. + +* (b) Where all of the cables are from 250 kcmil through 900 kcmil, the sum of the cross-sectional areas of all single-conductor cables shall not exceed the maximum allowable cable fill area in Column 1 of Table 392.22(B)(1) for the appropriate cable tray width. + +* (c) Where 1000 kcmil or larger single-conductor cables are installed in the same cable tray with single-conductor cables smaller than 1000 kcmil, the sum of the cross sectional areas of all cables smaller than 1000 kcmil shall not exceed the maximum allowable fill area resulting from the computation in Column 2 of Table 392.22(B)(1) for the appropriate cable tray width. + +* (d) Where any of the single conductor cables are 1/0 through 4/0 AWG, the sum of the diameters of all single conductor cables shall not exceed the cable tray width. + +##### 392.22(B)(2) Ventilated Channel Cable Trays. + +Where 50 mm (2 in.), 75 mm (3 in.), 100 mm (4 in.), or 150 mm (6 in.) wide ventilated channel cable trays contain single-conductor cables, the sum of the diameters of all single conductors shall not exceed the inside width of the channel. + +Table 392.22(B)(1) Allowable Cable Fill Area for Single-Conductor Cables in Ladder, + +Ventilated Trough, or Wire Mesh Cable Trays for Cables Rated 2000 Volts or Less + +Inside Width of Cable Tray + +Maximum Allowable Fill Area for Single-Conductor + +Cables in Ladder, Ventilated Trough, or Wire Mesh Cable Trays + +Column 1 + +Applicable for 392.22(B)(1)(b) + +Only + +Column 2 + +Applicable for 392.22(B)(1)(c) + +Only mm in. mm in. mm in. +50 2 1,400 2.0 1,400 – (28 Sd) 2.0 – (1.1 Sd) +100 4 2,800 4.5 2,800 – (28 Sd) 4.5 – (1.1 Sd) +150 6 4,200 6.5 4,200 – (28 Sd) 6.5 – (1.1 Sd) +200 8 5,600 8.5 5,600 – (28 Sd) 8.5 – (1.1 Sd) +225 9 6,100 9.5 6,100 – (28 Sd) 9.5 – (1.1 Sd) +300 12 8,400 13.0 8,400 – (28 Sd) 13.0 – (1.1 Sd) +400 16 11,200 17.5 11,200 – (28 Sd) 17.5 – (1.1 Sd) +2 2 2 2 a +2 2 2 2 b b b b + +Inside Width of Cable Tray + +Maximum Allowable Fill Area for Single-Conductor + +Cables in Ladder, Ventilated Trough, or Wire Mesh Cable Trays + +Column 1 + +Applicable for 392.22(B)(1)(b) + +Only + +Column 2 + +Applicable for 392.22(B)(1)(c) + +Only mm in. mm in. mm in. +450 18 12,600 19.5 12,600 – (28 Sd) 19.5 – (1.1 Sd) +500 20 14,000 21.5 14,000 – (28 Sd) 21.5 – (1.1 Sd) +600 24 16,800 26.0 16,800 – (28 Sd) 26.0 – (1.1 Sd) +750 30 21,000 32.5 21,000 – (28 Sd) 32.5 – (1.1 Sd) +900 36 25,200 39.0 25,200 – (28 Sd) 39.0 – (1.1 Sd) + +The maximum allowable fill areas in Column 2 shall be calculated. For example, the maximum allowable fill, in mm , for a 150-mm wide cable tray in Column 2 shall be 4200 minus (28 multiplied by Sd) \[the maximum allowable fill, in square inches, for a 6-in. wide cable tray in Column 2 shall be 6.5 minus (1.1 multiplied by Sd)\]. + +The term Sd in Column 2 is equal to the sum of the diameters, in mm, of all cables 507 mm (in inches, of all 1000 kcmil) and larger single-conductor cables in the same cable tray with small cables. + +#### 392.22(C) Number of Type MV and Type MC Cables (2001 Volts or Over) in Cable Trays. + +The number of cables rated 2001 volts or over permitted in a single cable tray shall not exceed the requirements of this section. + +The sum of the diameters of single-conductor and multiconductor cables shall not exceed the cable tray width, and the cables shall be installed in a single layer. Where single conductor cables are triplexed, quadruplexed, or bound together in circuit groups, the sum of the diameters of the single conductors shall not exceed the cable tray width, and these groups shall be installed in single layer arrangement. + +### 392.30 Securing and Supporting. + +#### 392.30(A) Cable Trays. + +Cable trays shall be supported at intervals in accordance with the installation instructions. + +#### 392.30(B) Cables and Conductors. + +Cables and conductors shall be secured to and supported by the cable tray system in accordance with (1), (2), (3), and (4) as applicable: + +* (1) In other than horizontal runs, the cables shall be fastened securely to transverse members of the cable tray. + +* (2) Supports shall be provided to prevent stress on cables where they enter raceways from cable tray systems. + +* (3) The system shall provide for the support of cables and raceway wiring methods in accordance with their corresponding articles. + +Where cable trays support individual conductors or multiconductor cables and where the conductors or multiconductor cables pass from one cable tray to another, or from a cable tray to raceway(s) or from a cable tray to equipment where the conductors are terminated, the distance between the cable trays or between the cable tray and the raceway(s) or the equipment shall not exceed 1.8 m (6 ft). The conductors shall be secured to the cable tray(s) at the transition, and they shall be protected, by guarding or by location, from physical damage. + +* (4) Cable ties shall be listed and identified for the application and for securement and support. + +### 392.44 Expansion Splice Plates. + +Expansion splice plates for cable trays shall be provided where necessary to compensate for thermal expansion and contraction. + +### 392.46 Bushed Conduit and Tubing. + +A box shall not be required where cables or conductors are installed in bushed conduit and tubing used for support or for protection against physical damage or where conductors or cables transition to a raceway wiring method from the cable tray. Conductors shall be permitted to enter equipment in accordance with 392.46(A) or (B). + +#### 392.46(A) Through Bushed Conduit or Tubing. + +Individual conductors or multiconductor cables with entirely nonmetallic sheaths shall be permitted to enter enclosures where they are terminated through nonflexible bushed conduit or tubing installed for their protection provided they are secured at the point of transition from the cable tray and the conduit or tubing is sealed at the outer end using an approved means so as to prevent debris from entering a +2 2 2 2 a 2 b 2 the equipment through the conduit or tubing. + +#### 392.46(B) Flanged Connections. + +Individual conductors or multiconductor cables with entirely nonmetallic sheaths shall be permitted to enter enclosures through openings associated with flanges from cable trays where the cable tray is attached to the flange and the flange is mounted directly to the equipment. The openings shall be made such that the conductors are protected from abrasion and the opening shall be sealed or covered to prevent debris from entering the enclosure through the opening. + +> [!info] Informational Note: +> One method of preventing debris from entering the enclosure is to seal the outer end of the raceway or the opening with duct seal. + +### 392.56 Cable Splices. + +Cable splices made and insulated by approved methods shall be permitted to be located within a cable tray, provided they are accessible. Splices shall be permitted to project above the side rails where not subject to physical damage. + +### 392.60 Grounding and Bonding. + +#### 392.60(A) Metal Cable Trays. + +Metal cable trays shall be permitted to be used as equipment grounding conductors where continuous maintenance and supervision ensure that qualified persons service the installed cable tray system and the cable tray complies with this section. Metal cable trays that support electrical conductors shall be grounded as required for conductor enclosures in accordance with 250.96 and Part IV of Article +250. Metal cable trays containing only non-power conductors shall be electrically continuous through approved connections or the use of a bonding jumper. + +> [!info] Informational Note: +> Examples of non-power conductors include nonconductive optical fiber cables and Class 2 and Class 3 remotecontrol, signaling, and power-limited circuits. + +#### 392.60(B) Steel or Aluminum Cable Tray Systems. + +Steel or aluminum cable tray systems shall be permitted to be used as equipment grounding conductors, provided all the following requirements are met: + +* (1) The cable tray sections and fittings are identified as an equipment grounding conductor. + +* (2) The minimum cross-sectional area of cable trays conform to the requirements in Table 392.60(B). + +* (3) All cable tray sections and fittings are legibly and durably marked to show the cross-sectional area of metal in channel cable trays, or cable trays of one-piece construction, and the total cross-sectional area of both side rails for ladder or trough cable trays. + +* (4) Cable tray sections, fittings, and connected raceways are bonded in accordance with 250.96, using bolted mechanical connectors or bonding jumpers sized and installed in accordance with 250.102. + +Table 392.60(B) Metal Area Requirements for Cable Trays Used as Equipment Grounding Conductor + +Maximum Fuse Ampere Rating, Circuit Breaker Ampere Trip Setting, or Circuit + +Breaker Protective Relay Ampere Trip Setting for Ground-Fault Protection of + +Any Cable Circuit in the Cable Tray System + +Minimum CrossSectional + +Area of + +Metal + +Steel + +Cable + +Trays + +Aluminum + +Cable + +Trays mm in. mm in. +60 129 0.20 129 0.20 +100 258 0.40 129 0.20 +200 451.5 0.70 129 0.20 +400 645 1.00 258 0.40 +600 967.5 1.50 258 0.40 +1000 — — 387 0.60 +1200 — — 645 1.00 +1600 — — 967.5 1.50 +* +2 2 2 2 +† + +Maximum Fuse Ampere Rating, Circuit Breaker Ampere Trip Setting, or Circuit + +Breaker Protective Relay Ampere Trip Setting for Ground-Fault Protection of + +Any Cable Circuit in the Cable Tray System + +Minimum CrossSectional + +Area of + +Metal + +Steel + +Cable + +Trays + +Aluminum + +Cable + +Trays mm in. mm in. +2000 — — 1290 2.00 + +Total cross-sectional area of both side rails for ladder or trough cable trays; or the minimum cross-sectional area of metal in channel cable trays or cable trays of one-piece construction. + +Steel cable trays shall not be used as equipment grounding conductors for circuits with ground-fault protection above 600 amperes. + +Aluminum cable trays shall not be used as equipment grounding conductors for circuits with ground-fault protection above 2000 amperes. + +#### 392.60(C) Transitions. + +Where metal cable tray systems are mechanically discontinuous, as permitted in 392.18(A), a bonding jumper sized in accordance with +250.102 shall connect the two sections of the cable tray, or the cable tray and the raceway or equipment. Bonding shall be in accordance with 250.96. + +### 392.80 Ampacity of Conductors. + +#### 392.80(A) Ampacity of Cables, Rated 2000 Volts or Less, in Cable Trays. + +> [!info] Informational Note: +> See 110.14(C) for conductor temperature limitations due to termination provisions. + +##### 392.80(A)(1) Multiconductor Cables. + +The ampacity of multiconductor cables, nominally rated 2000 volts or less, installed according to the requirements of 392.22(A) shall be as given in Table 310.16 and Table 310.18, subject to 392.80(A)(1)(a), (A)(1)(b), (A) (1)(c), and 310.14(A)(2). + +* (a) The adjustment factors of 310.15(C)(1) shall apply only to multiconductor cables with more than three current-carrying conductors. Adjustment factors shall be limited to the number of current-carrying conductors in the cable and not to the number of conductors in the cable tray. + +* (b) Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, not over 95 percent of the ampacities of Table 310.16 and Table 310.18 shall be permitted for multiconductor cables. + +* (c) Where multiconductor cables are installed in a single layer in uncovered trays, with a maintained spacing of not less than one cable diameter between cables, the ampacity shall not exceed the ambient temperature-corrected ampacities of multiconductor cables, with not more than three insulated conductors rated 0 through 2000 volts in free air, in accordance with 310.14(B). + +> [!info] Informational Note: +> See Informative Annex B, Table B(3). + +##### 392.80(A)(2) Single-Conductor Cables. + +The ampacity of single-conductor cables shall be as permitted by 310.14(A)(2). The adjustment factors of 310.15(C)(1) shall not apply to the ampacity of cables in cable trays. The ampacity of single-conductor cables, or single conductors cabled together (triplexed, quadruplexed, and so forth), nominally rated 2000 volts or less, shall comply with the following: + +* (a) Where installed according to the requirements of 392.22(B), the ampacities for 600 kcmil and larger single-conductor cables in uncovered cable trays shall not exceed 75 percent of the ampacities in Table 310.17 and Table 310.19. Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, the ampacities for 600 kcmil and larger cables shall not exceed 70 percent of the ampacities in Table 310.17 and Table 310.19. + +* (b) Where installed according to the requirements of 392.22(B), the ampacities for 1/0 AWG through 500 kcmil single-conductor cables in uncovered cable trays shall not exceed 65 percent of the ampacities in Table 310.17 and Table 310.19. Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, the ampacities for 1/0 AWG through 500 kcmil cables shall not exceed 60 percent of the ampacities in Table 310.17 and Table 310.19. + +* (c) Where single conductors are installed in a single layer in uncovered cable trays, with a maintained space of not less than one cable diameter between individual conductors, the ampacity of 1/0 AWG and larger cables shall not exceed the ampacities in + +Table 310.17 and Table 310.19. + +Exception to (2)(c): For solid bottom cable trays, the ampacity of single conductor cables shall be determined by 310.14(B). + +* (d) Where single conductors are installed in a triangular or square configuration in uncovered cable trays, with a maintained free +* +2 2 2 2 +† +* +† airspace of not less than 2.15 times one conductor diameter (2.15 × O.D.) of the largest conductor contained within the configuration and adjacent conductor configurations or cables, the ampacity of 1/0 AWG and larger cables shall not exceed the ampacities of two or three single insulated conductors rated 0 through 2000 volts supported on a messenger in accordance with +310.15. + +> [!info] Informational Note: +> See Table 310.20. + +##### 392.80(A)(3) Combinations of Multiconductor and Single-Conductor Cables. + +Where a cable tray contains a combination of multiconductor and single-conductor cables, the ampacities shall be as given in 392.80(A) + +* (1) for multiconductor cables and 392.80(A)(2) for single-conductor cables, provided that the following conditions apply: + +* (1) The sum of the multiconductor cable fill area as a percentage of the allowable fill area for the tray calculated in accordance with +392.22(A), and the single-conductor cable fill area as a percentage of the allowable fill area for the tray calculated in accordance with 392.22(B), totals not more than 100 percent. + +* (2) Multiconductor cables are installed according to 392.22(A), and single-conductor cables are installed according to 392.22(B) and 392.22(C). + +#### 392.80(B) Ampacity of Type MV and Type MC Cables (2001 Volts or Over) in Cable Trays. + +The ampacity of cables, rated 2001 volts, nominal, or over, installed according to 392.22(C) shall not exceed the requirements of this section. + +> [!info] Informational Note: +> See 110.40 for conductor temperature limitations due to termination provisions. + +##### 392.80(B)(1) Multiconductor Cables (2001 Volts or Over). + +The ampacity of multiconductor cables shall be as given in Table 311.60(C) (75) and Table 311.60(C)(76), subject to the following: + +* (1) Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, not more than 95 percent of the ampacities of Table 311.60(C)(75) and Table 311.60(C)(76) shall be permitted for multiconductor cables. + +* (2) Where multiconductor cables are installed in a single layer in uncovered cable trays, with maintained spacing of not less than one cable diameter between cables, the ampacity shall not exceed the allowable ampacities of Table 311.60(C)(71) and Table +311.60(C)(72). + +##### 392.80(B)(2) Single-Conductor Cables (2001 Volts or Over). + +The ampacity of single-conductor cables, or single conductors cabled together (triplexed, quadruplexed, and so forth), shall comply with the following: + +* (1) The ampacities for 1/0 AWG and larger single-conductor cables in uncovered cable trays shall not exceed 75 percent of the ampacities in Table 311.60(C)(69) and Table 311.60(C)(70). Where the cable trays are covered for more than 1.8 m (6 ft) with solid unventilated covers, the ampacities for 1/0 AWG and larger single-conductor cables shall not exceed 70 percent of the ampacities in Table 311.60(C)(69) and Table 311.60(C)(70). + +* (2) Where single-conductor cables are installed in a single layer in uncovered cable trays, with a maintained space of not less than one cable diameter between individual conductors, the ampacity of 1/0 AWG and larger cables shall not exceed the ampacities in Table 311.60(C)(69) and Table 311.60(C)(70). + +* (3) Where single conductors are installed in a triangular or square configuration in uncovered cable trays, with a maintained free air space of not less than 2.15 times the diameter (2.15 × O.D.) of the largest conductor contained within the configuration and adjacent conductor configurations or cables, the ampacity of 1/0 AWG and larger cables shall not exceed the ampacities in + +Table 311.60(C)(67) and Table 311.60(C)(68). + +## Part III. Construction Specifications + +### 392.100 Construction. + +#### 392.100(A) Strength and Rigidity. + +Cable trays shall have suitable strength and rigidity to provide adequate support for all contained wiring. + +#### 392.100(B) Smooth Edges. + +Cable trays shall not have sharp edges, burrs, or projections that could damage the insulation or jackets of the wiring. + +#### 392.100(C) Corrosion Protection. + +Cable tray systems shall be corrosion resistant. If made of ferrous material, the system shall be protected from corrosion as required by +300.6. + +#### 392.100(D) Side Rails. + +Cable trays shall have side rails or equivalent structural members. + +#### 392.100(E) Fittings. + +Cable trays shall include fittings or other suitable means for changes in direction and elevation of runs. + +#### 392.100(F) Nonmetallic Cable Tray. + +Nonmetallic cable trays shall be made of flame-retardant material. + +# Article 393 Low-Voltage Suspended Ceiling Power Distribution Systems + +## Part I. General + +### 393.1 Scope. + +This article covers the installation of low-voltage suspended ceiling power distribution systems. + +### 393.2 Definitions. + +The definitions in this section shall apply only within this article. + +Busbar. + +A noninsulated conductor electrically connected to the source of supply and physically supported on an insulator providing a power rail for connection to utilization equipment, such as sensors, actuators, A/V devices, low-voltage luminaire assemblies, and similar electrical equipment. + +Busbar Support. + +An insulator that runs the length of a section of suspended ceiling bus rail that serves to support and isolate the busbars from the suspended grid rail. + +Connector. + +A term used to refer to an electromechanical fitting. + +Connector, Load. + +An electromechanical connector used for power from the busbar to utilization equipment. + +Connector, Pendant. + +An electromechanical or mechanical connector used to suspend low-voltage luminaire or utilization equipment below the grid rail and to supply power to connect from the busbar to utilization equipment. + +Connector, Power Feed. + +An electromechanical connector used to connect the power supply to a power distribution cable, to connect directly to the busbar, or to connect from a power distribution cable to the busbar. + +Connector, Rail to Rail. + +An electromechanical connector used to interconnect busbars from one ceiling grid rail to another grid rail. + +Grid Bus Rail. + +A combination of the busbar, the busbar support, and the structural suspended ceiling grid system. + +Low-Voltage Suspended Ceiling Power Distribution System. + +A system that serves as a support for a finished ceiling surface and consists of a busbar and busbar support system to distribute power to utilization equipment supplied by a Class 2 power supply. + +Power Supply. + +A Class 2 power supply connected between the branch-circuit power distribution system and the busbar low-voltage suspended ceiling power distribution system. + +Rail. + +The structural support for the suspended ceiling system typically forming the ceiling grid supporting the ceiling tile and listed utilization equipment, such as sensors, actuators, A/V devices, and low-voltage luminaires and similar electrical equipment. + +Reverse Polarity Protection (Backfeed Protection). + +A system that prevents two interconnected power supplies, connected positive to negative, from passing current from one power source into a second power source. + +Suspended Ceiling Grid. + +A system that serves as a support for a finished ceiling surface and other utilization equipment. + +### 393.6 Listing Requirements. + +Suspended ceiling power distribution systems and associated fittings shall be listed as in 393.6(A) or (B). + +#### 393.6(A) Listed System. + +Low-voltage suspended ceiling distribution systems operating at 30 volts ac or less or 60 volts dc or less shall be listed as a complete system, with the utilization equipment, power supply, and fittings as part of the same identified system. + +#### 393.6(B) Assembly of Listed Parts. + +A low-voltage suspended ceiling power distribution system assembled from the following parts, listed according to the appropriate function, shall be permitted: + +* (1) Listed low-voltage utilization equipment + +* (2) Listed Class 2 power supply + +* (3) Listed or identified fittings, including connectors and grid rails with bare conductors + +* (4) Listed low-voltage cables in accordance with 725.179, conductors in raceways, or other fixed wiring methods for the secondary circuit + +## Part II. Installation + +### 393.10 Uses Permitted. + +Low-voltage suspended ceiling power distribution systems shall be permanently connected and shall be permitted as follows: + +* (1) For listed utilization equipment capable of operation at a maximum of 30 volts ac (42.4 volts peak) or 60 volts dc (24.8 volts peak for dc interrupted at a rate of 10 Hz to 200 Hz) and limited to Class 2 power levels in Chapter 9, Table 11(A) and Table +11(B) for lighting, control, and signaling circuits. + +* (2) In indoor dry locations. + +* (3) For residential, commercial, and industrial installations. + +* (4) In other spaces used for environmental air in accordance with 300.22(C), electrical equipment having a metal enclosure, or with a nonmetallic enclosure and fittings, shall be listed for use within an air-handling space and shall have adequate fire-resistant and low-smoke-producing characteristics and associated wiring material suitable for the ambient temperature. + +> [!info] Informational Note: +> One method of defining adequate fire-resistant and low-smoke-producing characteristics for electrical equipment with a nonmetallic enclosure is in ANSI/ UL 2043-2013, Fire Test for Heat and Visible Smoke Release for Discrete + +Products and Their Accessories Installed in Air-Handling Spaces. + +### 393.12 Uses Not Permitted. + +Suspended ceiling power distribution systems shall not be installed in the following: + +* (1) In damp or wet locations + +* (2) Where subject to corrosive fumes or vapors, such as storage battery rooms + +* (3) Where subject to physical damage + +* (4) In concealed locations + +* (5) In hazardous (classified) locations + +* (6) As part of a fire-rated floor-ceiling or roof-ceiling assembly, unless specifically listed as part of the assembly + +* (7) For lighting in general or critical patient care areas + +### 393.14 Installation. + +#### 393.14(A) General Requirements. + +Support wiring shall be installed in a neat and workmanlike manner. Cables and conductors installed exposed on the surface of ceilings and sidewalls shall be supported by the building structure in such a manner that the cable is not damaged by normal building use. Such cables shall be supported by straps, staples, hangers, cable ties listed and identified for securement and support, or similar fittings designed and installed so as not to damage the cable. + +> [!info] Informational Note: +> Suspended ceiling low-voltage power grid distribution systems should be installed by qualified persons in accordance with the manufacturer’s installation instructions. + +#### 393.14(B) Insulated Conductors. + +Exposed insulated secondary circuit conductors shall be listed, of the type, and installed as described as follows: + +* (1) Class 2 cable supplied by a listed Class 2 power source and installed in accordance with Parts I and III of Article 725 + +* (2) Wiring methods described in Chapter 3 + +### 393.21 Disconnecting Means. + +#### 393.21(A) Location. + +A disconnecting means for the Class 2 supply to the power grid system shall be located so as to be accessible and within sight of the + +Class 2 power source for servicing or maintenance of the grid system. + +#### 393.21(B) Multiwire Branch Circuits. + +Where connected to a multiwire branch circuit, the disconnecting means shall simultaneously disconnect all the supply conductors, including the grounded conductors. + +### 393.30 Securing and Supporting. + +#### 393.30(A) Attached to Building Structure. + +A suspended ceiling low-voltage power distribution system shall be secured to the mounting surface of the building structure by hanging wires, screws, or bolts in accordance with the installation and operation instructions. Mounting hardware, such as screws or bolts, shall be either packaged with the suspended ceiling low-voltage lighting power distribution system, or the installation instructions shall specify the types of mounting fasteners to be used. + +#### 393.30(B) Attachment of Power Grid Rails. + +The individual power grid rails shall be mechanically secured to the overall ceiling grid assembly. + +### 393.40 Connectors and Enclosures. + +#### 393.40(A) Connectors. + +Connections to busbar grid rails, cables, and conductors shall be made with listed insulating devices, and these connections shall be accessible after installation. A soldered connection shall be made mechanically secure before being soldered. Other means of securing leads, such as push-on terminals and spade-type connectors, shall provide a secure mechanical connection. The following connectors shall be permitted to be used as connection or interconnection devices: + +* (1) Load connectors shall be used for power from the busbar to listed utilization equipment. + +* (2) A pendant connector shall be permitted to suspend low-voltage luminaires or utilization equipment below the grid rail and to supply power from the busbar to the utilization equipment. + +* (3) A power feed connector shall be permitted to connect the power supply directly to a power distribution cable and to the busbar. + +* (4) Rail-to-rail connectors shall be permitted to interconnect busbars from one ceiling grid rail to another grid rail. + +> [!info] Informational Note: +> For quick-connect terminals, see UL 310, Standard for Electrical Quick-Connect, and for mechanical splicing devices, see UL 486A-486B, Standard for Wire Connectors. + +#### 393.40(B) Enclosures. + +Where made in a wall, connections shall be installed in an enclosure in accordance with Parts I, II, and III of Article 314. + +### 393.45 Overcurrent and Reverse Polarity (Backfeed) Protection. + +#### 393.45(A) Overcurrent Protection. + +The listed Class 2 power supply or transformer primary shall be protected at not greater than 20 amperes. + +#### 393.45(B) Interconnection of Power Sources. + +Listed Class 2 sources shall not have the output connections paralleled or otherwise interconnected unless listed for such interconnection. + +#### 393.45(C) Reverse Polarity (Backfeed) Protection of Direct-Current Systems. + +A suspended ceiling low-voltage power distribution system shall be permitted to have reverse polarity (backfeed) protection of dc circuits by one of the following means: + +* (1) If the power supply is provided as part of the system, the power supply is provided with reverse polarity (backfeed) protection; or + +* (2) If the power supply is not provided as part of the system, reverse polarity or backfeed protection can be provided as part of the grid rail busbar or as a part of the power feed connector. + +### 393.56 Splices. + +A busbar splice shall be provided with insulation and mechanical protection equivalent to that of the grid rail busbars involved. + +### 393.57 Connections. + +Connections in busbar grid rails, cables, and conductors shall be made with listed insulating devices and be accessible after installation. Where made in a wall, connections shall be installed in an enclosure in accordance with Parts I, II, and III of Article 314, as applicable. + +### 393.60 Grounding. + +#### 393.60(A) Grounding of Supply Side of Class 2 Power Source. + +The supply side of the Class 2 power source shall be connected to an equipment grounding conductor in accordance with the applicable requirements in Part IV of Article 250. + +#### 393.60(B) Grounding of Load Side of Class 2 Power Source. + +Class 2 load side circuits for suspended ceiling low-voltage power grid distribution systems shall not be grounded. + +## Part III. Construction Specifications + +### 393.104 Sizes and Types of Conductors. + +#### 393.104(A) Load Side Utilization Conductor Size. + +Current-carrying conductors for load side utilization equipment shall be copper and shall be 18 AWG minimum. + +> [!important] Exception: +> Conductors of a size smaller than 18 AWG, but not smaller than 24 AWG, shall be permitted to be used for Class 2 circuits. + +Where used, these conductors shall be installed using a Chapter 3 wiring method, shall be totally enclosed, shall not be subject to movement or strain, and shall comply with the ampacity requirements in Table 522.22. + +#### 393.104(B) Power Feed Bus Rail Conductor Size. + +The power feed bus rail shall be 16 AWG minimum or equivalent. For a busbar with a circular cross section, the diameter shall be +1.29 mm (0.051 in.) minimum, and, for other than circular busbars, the area shall be 1.32 mm (0.002 in. ) minimum. + +# Article 394 Concealed Knob-and-Tube Wiring + +## Part I. General + +### 394.1 Scope. + +This article covers the use, installation, and construction specifications of concealed knob-and-tube wiring. + +### 394.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Concealed Knob-and-Tube Wiring. + +A wiring method using knobs, tubes, and flexible nonmetallic tubing for the protection and support of single insulated conductors. + +## Part II. Installation + +### 394.10 Uses Permitted. + +Concealed knob-and-tube wiring shall be permitted to be installed in the hollow spaces of walls and ceilings, or in unfinished attics and roof spaces as provided by 394.23, only as follows: +2 2 + +* (1) For extensions of existing installations + +* (2) Elsewhere by special permission + +### 394.12 Uses Not Permitted. + +Concealed knob-and-tube wiring shall not be used in the following: + +* (1) Commercial garages + +* (2) Theaters and similar locations + +* (3) Motion picture studios + +* (4) Hazardous (classified) locations + +* (5) Hollow spaces of walls, ceilings, and attics where such spaces are insulated by loose, rolled, or foamed-in-place insulating material that envelops the conductors + +### 394.17 Through or Parallel to Framing Members. + +Conductors shall comply with 398.17 where passing through holes in structural members. Where passing through wood cross members in plastered partitions, conductors shall be protected by noncombustible, nonabsorbent, insulating tubes extending not less than 75 mm +(3 in.) beyond the wood member. + +### 394.19 Clearances. + +#### 394.19(A) General. + +A clearance of not less than 75 mm (3 in.) shall be maintained between conductors and a clearance of not less than 25 mm (1 in.) between the conductor and the surface over which it passes. + +#### 394.19(B) Limited Conductor Space. + +Where space is too limited to provide these minimum clearances, such as at meters, panelboards, outlets, and switch points, the individual conductors shall be enclosed in flexible nonmetallic tubing, which shall be continuous in length between the last support and the enclosure or terminal point. + +#### 394.19(C) Clearance from Piping, Exposed Conductors, and So Forth. + +Conductors shall comply with 398.19 for clearances from other exposed conductors, piping, and so forth. + +### 394.23 In Accessible Attics. + +Conductors in unfinished attics and roof spaces shall comply with 394.23(A) or (B). + +> [!info] Informational Note: +> See 310.14(A)(3) for temperature limitation of conductors. + +#### 394.23(A) Accessible by Stairway or Permanent Ladder. + +Conductors shall be installed along the side of or through bored holes in floor joists, studs, or rafters. Where run through bored holes, conductors in the joists and in studs or rafters to a height of not less than 2.1 m (7 ft) above the floor or floor joists shall be protected by substantial running boards extending not less than 25 mm (1 in.) on each side of the conductors. Running boards shall be securely fastened in place. Running boards and guard strips shall not be required where conductors are installed along the sides of joists, studs, or rafters. + +#### 394.23(B) Not Accessible by Stairway or Permanent Ladder. + +Conductors shall be installed along the sides of or through bored holes in floor joists, studs, or rafters. + +> [!important] Exception: +> In buildings completed before the wiring is installed, attic and roof spaces that are not accessible by stairway or permanent ladder and have headroom at all points less than 900 mm (3 ft), the wiring shall be permitted to be installed on the edges of rafters or joists facing the attic or roof space. + +### 394.30 Securing and Supporting. + +#### 394.30(A) Supporting. + +Conductors shall be rigidly supported on noncombustible, nonabsorbent insulating materials and shall not contact any other objects. + +Supports shall be installed as follows: + +* (1) Within 150 mm (6 in.) of each side of each tap or splice, and + +* (2) At intervals not exceeding 1.4 m (41⁄2 ft). + +Where it is impracticable to provide supports, conductors shall be permitted to be fished through hollow spaces in dry locations, provided each conductor is individually enclosed in flexible nonmetallic tubing that is in continuous lengths between supports, between boxes, or between a support and a box. + +#### 394.30(B) Securing. + +Where solid knobs are used, conductors shall be securely tied thereto by tie wires having insulation equivalent to that of the conductor. + +### 394.42 Devices. + +Switches shall comply with 404.4 and 404.10(B). + +### 394.56 Splices and Taps. + +Splices shall be soldered unless approved splicing devices are used. In-line or strain splices shall not be used. + +## Part III. Construction Specifications + +### 394.104 Conductors. + +Conductors shall be of a type specified by Article 310. + +# Article 396 Messenger-Supported Wiring + +## Part I. General + +### 396.1 Scope. + +This article covers the use, installation, and construction specifications for messenger-supported wiring. + +### 396.2 Definitions. + +Insulated Conductor. + +This definition shall apply only within this article. + +For the purposes of this article, an insulated conductor includes the following: + +* (1) Conductor types described in 310.4, and + +* (2) Overhead service conductors encased in a polymeric material that has been evaluated for the applied nominal voltage. + +> [!info] Informational Note: +> Evidence of evaluation for the applied nominal voltage can be given by certification that the conductors have met the requirements of ICEA S-76-474-2011, Standard for Neutral Supported Power Cable Assemblies with Weather-Resistant Extruded + +Insulation Rated 600 Volts. + +Messenger-Supported Wiring. + +This definition shall apply within this article and throughout the Code. + +An exposed wiring support system using a messenger wire to support insulated conductors by any one of the following: + +* (1) A messenger with rings and saddles for conductor support + +* (2) A messenger with a field-installed lashing material for conductor support + +* (3) Factory-assembled aerial cable + +* (4) Multiplex cables utilizing a bare conductor, factory assembled and twisted with one or more insulated conductors, such as duplex, triplex, or quadruplex type of construction + +## Part II. Installation + +### 396.10 Uses Permitted. + +#### 396.10(A) Cable Types. + +The cable types in Table 396.10(A) shall be permitted to be installed in messenger-supported wiring under the conditions described in the article or section referenced for each. + +Table 396.10(A) Cable Types + +Cable Type Section Article + +Cable Type Section Article + +Medium-voltage cable 328 + +Metal-clad cable 330 + +Mineral-insulated, metal-sheathed cable 332 + +Multiconductor service-entrance cable 338 + +Multiconductor underground feeder and branch-circuit cable 340 + +Other factory-assembled, multiconductor control, signal, or power cables that are identified for the use + +Power and control tray cable 336 + +Power-limited tray cable Table 725.154, 725.135(J), and +725.179(E) + +#### 396.10(B) In Industrial Establishments. + +In industrial establishments only, where conditions of maintenance and supervision ensure that only qualified persons service the installed messenger-supported wiring, the following shall be permitted: + +* (1) Any of the conductor types shown in Table 310.4(A) or Table 310.4(B) + +* (2) MV cable + +Where exposed to weather, conductors shall be listed for use in wet locations. Where exposed to direct rays of the sun, conductors or cables shall be sunlight resistant. + +#### 396.10(C) Hazardous (Classified) Locations. + +Messenger-supported wiring shall be permitted to be used in hazardous (classified) locations where the contained cables and messenger-supported wiring are specifically permitted by other articles in this Code. + +### 396.12 Uses Not Permitted. + +Messenger-supported wiring shall not be used in hoistways or where subject to physical damage. + +### 396.30 Messenger. + +#### 396.30(A) Support. + +The messenger shall be supported at dead ends and at intermediate locations so as to eliminate tension on the conductors. The conductors shall not be permitted to come into contact with the messenger supports or any structural members, walls, or pipes. + +#### 396.30(B) Neutral Conductor. + +Where the messenger is used as a neutral conductor, it shall comply with the requirements of 225.4, 250.184(A), 250.184(B)(7), and +250.187(B). + +#### 396.30(C) Equipment Grounding Conductor. + +Where the messenger is used as an equipment grounding conductor, it shall comply with the requirements of 250.32(B), 250.118, +250.184(B)(8), and 250.187(D). + +### 396.56 Conductor Splices and Taps. + +Conductor splices and taps made and insulated by approved methods shall be permitted in messenger-supported wiring. + +### 396.60 Grounding. + +The messenger shall be grounded as required by 250.80 and 250.86 for enclosure grounding. + +# Article 398 Open Wiring on Insulators + +## Part I. General + +### 398.1 Scope. + +This article covers the use, installation, and construction specifications of open wiring on insulators. + +### 398.2 Definition. + +The definition in this section shall apply within this article and throughout the Code. + +Open Wiring on Insulators. + +An exposed wiring method using cleats, knobs, tubes, and flexible tubing for the protection and support of single insulated conductors run in or on buildings. + +## Part II. Installation + +### 398.10 Uses Permitted. + +Open wiring on insulators shall be permitted only for industrial or agricultural establishments on systems of 1000 volts, nominal, or less, as follows: + +* (1) Indoors or outdoors + +* (2) In wet or dry locations + +* (3) Where subject to corrosive vapors + +* (4) For services + +### 398.12 Uses Not Permitted. + +Open wiring on insulators shall not be installed where concealed by the building structure. + +### 398.15 Exposed Work. + +#### 398.15(A) Dry Locations. + +In dry locations, where not exposed to physical damage, conductors shall be permitted to be separately enclosed in flexible nonmetallic tubing. The tubing shall be in continuous lengths not exceeding 4.5 m (15 ft) and secured to the surface by straps at intervals not exceeding 1.4 m (41⁄2 ft). + +#### 398.15(B) Entering Spaces Subject to Dampness, Wetness, or Corrosive Vapors. + +Conductors entering or leaving locations subject to dampness, wetness, or corrosive vapors shall have drip loops formed on them and shall then pass upward and inward from the outside of the buildings, or from the damp, wet, or corrosive location, through noncombustible, nonabsorbent insulating tubes. + +> [!info] Informational Note: +> See 230.52 for individual conductors entering buildings or other structures. + +#### 398.15(C) Exposed to Physical Damage. + +Conductors within 2.1 m (7 ft) from the floor shall be considered exposed to physical damage. Where open conductors cross ceiling joists and wall studs and are exposed to physical damage, they shall be protected by one of the following methods: + +* (1) Guard strips not less than 25 mm (1 in.) nominal in thickness and at least as high as the insulating supports, placed on each side of and close to the wiring. + +* (2) A substantial running board at least 13 mm (1⁄2 in.) thick in back of the conductors with side protections. Running boards shall extend at least 25 mm (1 in.) outside the conductors, but not more than 50 mm (2 in.), and the protecting sides shall be at least +50 mm (2 in.) high and at least 25 mm (1 in.), nominal, in thickness. + +* (3) Boxing made in accordance with 398.15(C)(1) or (C)(2) and furnished with a cover kept at least 25 mm (1 in.) away from the conductors within. Where protecting vertical conductors on side walls, the boxing shall be closed at the top and the holes through which the conductors pass shall be bushed. + +* (4) Rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing. When installed in metal piping, the conductors shall be encased in continuous lengths of approved flexible tubing. + +### 398.17 Through or Parallel to Framing Members. + +Open conductors shall be separated from contact with walls, floors, wood cross members, or partitions through which they pass by tubes or bushings of noncombustible, nonabsorbent insulating material. Where the bushing is shorter than the hole, a waterproof sleeve of noninductive material shall be inserted in the hole and an insulating bushing slipped into the sleeve at each end in such a manner as to keep the conductors absolutely out of contact with the sleeve. Each conductor shall be carried through a separate tube or sleeve. + +> [!info] Informational Note: +> See 310.14(A)(3) for temperature limitation of conductors. + +### 398.19 Clearances. + +Open conductors shall be separated at least 50 mm (2 in.) from metal raceways, piping, or other conducting material, and from any exposed lighting, power, or signaling conductor, or shall be separated therefrom by a continuous and firmly fixed nonconductor in addition to the insulation of the conductor. Where any insulating tube is used, it shall be secured at the ends. Where practicable, conductors shall pass over rather than under any piping subject to leakage or accumulations of moisture. + +### 398.23 In Accessible Attics. + +Conductors in unfinished attics and roof spaces shall comply with 398.23(A) or (B). + +#### 398.23(A) Accessible by Stairway or Permanent Ladder. + +Conductors shall be installed along the side of or through bored holes in floor joists, studs, or rafters. Where run through bored holes, conductors in the joists and in studs or rafters to a height of not less than 2.1 m (7 ft) above the floor or floor joists shall be protected by substantial running boards extending not less than 25 mm (1 in.) on each side of the conductors. Running boards shall be securely fastened in place. Running boards and guard strips shall not be required for conductors installed along the sides of joists, studs, or rafters. + +#### 398.23(B) Not Accessible by Stairway or Permanent Ladder. + +Conductors shall be installed along the sides of or through bored holes in floor joists, studs, or rafters. + +> [!important] Exception: +> In buildings completed before the wiring is installed, in attic and roof spaces that are not accessible by stairway or permanent ladder and have headroom at all points less than 900 mm (3 ft), the wiring shall be permitted to be installed on the edges of rafters or joists facing the attic or roof space. + +### 398.30 Securing and Supporting. + +#### 398.30(A) Conductor Sizes Smaller Than 8 AWG. + +Conductors smaller than 8 AWG shall be rigidly supported on noncombustible, nonabsorbent insulating materials and shall not contact any other objects. Supports shall be installed as follows: + +* (1) Within 150 mm (6 in.) from a tap or splice + +* (2) Within 300 mm (12 in.) of a dead-end connection to a lampholder or receptacle + +* (3) At intervals not exceeding 1.4 m (41⁄2 ft) and at closer intervals sufficient to provide adequate support where likely to be disturbed + +#### 398.30(B) Conductor Sizes 8 AWG and Larger. + +Supports for conductors 8 AWG or larger installed across open spaces shall be permitted up to 4.5 m (15 ft) apart if noncombustible, nonabsorbent insulating spacers are used at least every 1.4 m (41⁄2 ft) to maintain at least 65 mm (21⁄2 in.) between conductors. + +Where not likely to be disturbed in buildings of mill construction, 8 AWG and larger conductors shall be permitted to be run across open spaces if supported from each wood cross member on approved insulators maintaining 150 mm (6 in.) between conductors. + +#### 398.30(C) Industrial Establishments. + +In industrial establishments only, where conditions of maintenance and supervision ensure that only qualified persons service the system, conductors of sizes 250 kcmil and larger shall be permitted to be run across open spaces where supported at intervals up to +9.0 m (30 ft) apart. + +#### 398.30(D) Mounting of Conductor Supports. + +Where nails are used to mount knobs, they shall not be smaller than tenpenny. Where screws are used to mount knobs, or where nails or screws are used to mount cleats, they shall be of a length sufficient to penetrate the wood to a depth equal to at least one-half the height of the knob and the full thickness of the cleat. Cushion washers shall be used with nails. + +#### 398.30(E) Tie Wires. + +Conductors 8 AWG or larger and supported on solid knobs shall be securely tied thereto by tie wires having an insulation equivalent to that of the conductor. + +### 398.42 Devices. + +Surface-type snap switches shall be mounted in accordance with 404.10(A), and boxes shall not be required. Other type switches shall be installed in accordance with 404.4. + +## Part III. Construction Specifications + +### 398.104 Conductors. + +Conductors shall be of a type specified by Article 310. + +# Article 399 Outdoor Overhead Conductors over 1000 Volts + +### 399.1 Scope. + +This article covers the use and installation for outdoor overhead conductors over 1000 volts, nominal. + +### 399.2 Definition. + +The definitions in this section shall apply only within this article. + +Outdoor Overhead Conductors. + +Single conductors, insulated, covered, or bare, installed outdoors on support structures in free air. + +### 399.10 Uses Permitted. + +Outdoor overhead conductors over 1000 volts, nominal, shall be permitted only for systems rated over 1000 volts, nominal, as follows: + +* (1) Outdoors in free air + +* (2) For service conductors, feeders, or branch circuits + +> [!info] Informational Note: +> For additional information on outdoor overhead conductors over 1000 volts, see IEEE C2, National Electrical Safety + +Code, and ANSI/IEEE 3001.2, Recommended Practice for Evaluating the Electrical Service Requirements of Industrial and Commercial + +Power Systems. + +### 399.30 Support. + +#### 399.30(A) Conductors. + +Documentation of the engineered design by a licensed professional engineer engaged primarily in the design of such systems for the spacing between conductors shall be available upon request of the authority having jurisdiction and shall include consideration of the following: + +* (1) Applied voltage + +* (2) Conductor size + +* (3) Distance between support structures + +* (4) Type of structure + +* (5) Wind/ice loading + +* (6) Surge protection + +#### 399.30(B) Structures. + +Structures of wood, metal, or concrete, or combinations of those materials, shall be provided for support of overhead conductors over +1000 volts, nominal. Documentation of the engineered design by a licensed professional engineer engaged primarily in the design of such systems and the installation of each support structure shall be available upon request of the authority having jurisdiction and shall include consideration of the following: + +* (1) Soil conditions + +* (2) Foundations and structure settings + +* (3) Weight of all supported conductors and equipment + +* (4) Weather loading and other conditions such as, but not limited to, ice, wind, temperature, and lightning + +* (5) Angle where change of direction occurs + +* (6) Spans between adjacent structures + +* (7) Effect of dead-end structures + +* (8) Strength of guy wires and guy anchors + +* (9) Structure size and material(s) + +* (10) Hardware + +#### 399.30(C) Insulators. + +Insulators used to support conductors shall be rated for all of the following: + +* (1) Applied phase-to-phase voltage + +* (2) Mechanical strength required for each individual installation + +* (3) Impulse withstand BIL in accordance with Table 490.24 + +> [!info] Informational Note: +> 399.30(A), (B), and (C) are not all-inclusive lists. diff --git a/nfpa-70_national-electric-code.md b/nfpa-70_national-electric-code.md index e3faabf..bd8a07d 100644 --- a/nfpa-70_national-electric-code.md +++ b/nfpa-70_national-electric-code.md @@ -19,7 +19,7 @@ title: "NFPA 70: National Electric Code" ## Chapter 1 General * [[nfpa-70_100_definitions|100 Definitions]] -* [[nfpa-70_110_requirements-for-electrical-installations|110 Requirements for Electrical Installations]] +* [[nfpa-70_110_requirements|110 Requirements for Electrical Installations]] ## Chapter 2 Wiring and Protection @@ -31,21 +31,21 @@ title: "NFPA 70: National Electric Code" * [[nfpa-70_230_services|230 Services]] * [[nfpa-70_240_overcurrent-protection|240 Overcurrent Protection]] * [[nfpa-70_242|242 Overvoltage Protection]] -* [[nfpa-70_250_grounding-and-bonding|250 Grounding and Bonding]] +* [[nfpa-70_250_grounding|250 Grounding and Bonding]] ## Chapter 3 Wiring Methods and Materials * [[nfpa-70_300_general-requirements|300 General Requirements for Wiring Methods and Materials]] * [[nfpa-70_310_conductors_for_general_wiring|310 Conductors for General Wiring]] -* [[nfpa-70_311|311 Medium Voltage Conductors and Cable]] -* [[nfpa-70_312|312 Cabinets, Cutout Boxes, and Meter Socket Enclosures]] +* [[nfpa-70_311_mv-conductors|311 Medium Voltage Conductors and Cable]] +* [[nfpa-70_312_cabinets|312 Cabinets, Cutout Boxes, and Meter Socket Enclosures]] * [[nfpa-70_314_boxes|314 Outlet, Device, Pull, and Junction Boxes; Conduit Bodies; Fittings; and Handhole Enclosures]] * [[nfpa-70_320_armored-cable|320 Armored Cable: Type AC]] * [[nfpa-70_322|322 Flat Cable Assemblies: Type FC]] * [[nfpa-70_324|324 Flat Conductor Cable: Type FCC]] * [[nfpa-70_326|326 Integrated Gas Spacer Cable: Type IGS]] -* [[nfpa-70_330|330 Metal-Clad Cable: Type MC]] -* [[nfpa-70_332|332 Mineral-Insulated, Metal-Sheathed Cable: Type MI]] +* [[nfpa-70_330_mc-cable|330 Metal-Clad Cable: Type MC]] +* [[nfpa-70_332_mi-cable|332 Mineral-Insulated, Metal-Sheathed Cable: Type MI]] * [[nfpa-70_334_nm-cable|334 Nonmetallic-Sheathed Cable: Types NM and NMC]] * [[nfpa-70_336|336 Power and Control Tray Cable: Type TC]] * [[nfpa-70_337|337 Type P Cable]] @@ -93,7 +93,7 @@ title: "NFPA 70: National Electric Code" * [[nfpa-70_409|409 Industrial Control Panels]] * [[nfpa-70_410|410 Luminaires, Lampholders, and Lamps]] * [[nfpa-70_411|411 Low-Voltage Lighting]] -* [[nfpa-70_422|422 Appliances]] +* [[nfpa-70_422_appliances|422 Appliances]] * [[nfpa-70_424|424 Fixed Electric Space-Heating Equipment]] * [[nfpa-70_425|425 Fixed Resistance and Electrode Industrial Process Heating Equipment]] * [[nfpa-70_426|426 Fixed Outdoor Electric Deicing and Snow-Melting Equipment]] diff --git a/raceway-terms.md b/raceway-terms.md index 36c9d99..33db00a 100644 --- a/raceway-terms.md +++ b/raceway-terms.md @@ -32,7 +32,7 @@ title: Raceway Terms "Wiring method" is not given explicit definition in the NEC. -![[nfpa-70_110_requirements-for-electrical-installations#110.8 Wiring Methods]] +![[nfpa-70_110_requirements#110.8 Wiring Methods]] ![[nfpa-70_300_general-requirements#300.1(A) All Wiring Installations.]] diff --git a/sleeving-takeoff.md b/sleeving-takeoff.md index 88d7b90..f86c711 100644 --- a/sleeving-takeoff.md +++ b/sleeving-takeoff.md @@ -11,18 +11,37 @@ title: Sleeving Takeoff --- # Sleeving Takeoff -Provide sleeves for all conduits passing through floors. +## Application + +Provide sleeves for all conduits passing through floors, +as well as any additional sleeves shown on the drawings. + +## Note: Application + +The term "sleeve" may refer to + +* a short length of conduit + +* a Hilti-type firestop sleeve assembly + +* a short length of conduit + _in_ a Hilti-type firestop sleeve assembly + +Seek additional clarification. + +## Breakdowns + +* `Area` = "01 - Feeders/Risers ..." +* `Phase` = "Feeders" +* `System` = "FRR - Feeders and Risers" + +For all sleeving, regardless of application. + +## Item Selection `ITEM DATABASE`/`HILTI`/`CAST-IN DEVICE CP 680-...` -* _Plastic Conduit:_ P -* _Metal Conduit:_ M +* **CP 680-P** --- For plastic conduit +* **CP 680-M** --- For metal conduit -> [!important] -> The term "sleeve" may refer to -> * a short length of conduit -> * a Hilti-type firestop sleeve assembly -> * a short length of conduit -> _in_ a Hilti-type firestop sleeve assembly -> -> Seek additional clarification. +See [Hilti USA](https://www.hilti.com/). diff --git a/templates/nec-article.md b/templates/nec-article.md new file mode 100644 index 0000000..783fed9 --- /dev/null +++ b/templates/nec-article.md @@ -0,0 +1,13 @@ +--- +id: +aliases: + - nec-??? +tags: + - authorship/other + - destiny/permanent/entry-point + - exclude-from-word-count + - status/incomplete + - topic/construction/electrical + - type/media +title: "" +---