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2025-12-02.md
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---
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
2025-12-03.md
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---
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.
alternating-current.md
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@@ -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.
conductor-sizing.md
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@@ -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)
electrical-takeoff.md
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@@ -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".
feeders-takeoff.md
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@@ -25,7 +25,7 @@ All feeder takeoff descriptions should be prefixed with `<parent> TO <child>`
> [!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`/...
fire-resistive-wiring-methods-takeoff.md
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@@ -21,3 +21,4 @@ or concrete-encasement can fulfill this requirement.
If "Lifeline" (cable-in-conduit) cable is used,
utilize EMT-Comp assemblies.
fire-resistive-wiring-methods.md
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@@ -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)
multi-family-dwellings.md
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@@ -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
nfpa-70_100_definitions.md
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@@ -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.
nfpa-70_110_requirements-for-electrical-installations.md → nfpa-70_110_requirements.md
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@@ -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
nfpa-70_210_branch-circuits.md
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@@ -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.
nfpa-70_215_feeders.md
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@@ -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
nfpa-70_220_load-calculations.md
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@@ -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
nfpa-70_230_services.md
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@@ -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
nfpa-70_240_overcurrent-protection.md
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@@ -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.
nfpa-70_250_grounding-and-bonding.md → nfpa-70_250_grounding.md
+66 -66
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@@ -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.
nfpa-70_300_general-requirements.md
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nfpa-70_310_conductors_for_general_wiring.md
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@@ -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.
<!-- TODO: TEXT OMITTED -->
### 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 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 -->
%% TABLE OMITTED %%
<!-- TODO: TEXT 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.
<!-- TODO: TEXT OMITTED -->
#### 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.
<!-- TODO: TEXT OMITTED -->
> [!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** -->
%% 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).
<!-- TODO: fix prime notation -->
##### 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 -->
%% 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 -->
%% 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.
<!-- TODO: TEXT OMITTED -->
##### 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.
<!-- TODO: TEXT OMITTED -->
#### 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 %%
nfpa-70_311_mv-conductors.md
+1993
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nfpa-70_312_cabinets.md
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@@ -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.
nfpa-70_314_boxes.md
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@@ -15,20 +15,438 @@ title: Article 314 Outlet, Device, Pull, and Junction Boxes; Conduit Bodies; Fit
## Part I. Scope and General
<!-- TODO: TEXT OMITTED -->
### 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
<!-- TODO: TEXT OMITTED -->
### 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 cm<sup>3</sup> (1⁄2 in.<sup>3</sup>) if metal, and 16.4 cm (1.0 in.<sup>3</sup>) 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 cm<sup>3</sup> (100 in.<sup>3</sup>) 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 cm<sup>3</sup>(100 in.<sup>3</sup>) 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.
<!-- TODO: TEXT OMITTED -->
#### 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 cm<sup>3</sup>(100 in.<sup>3</sup>) 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 cm<sup>3</sup> (100 in.<sup>3</sup>).
Metal boxes over 1650 cm<sup>3</sup> (100 in.<sup>3</sup>) 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.
nfpa-70_320_armored-cable.md
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@@ -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"
nfpa-70_330_mc-cable.md
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---
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.
nfpa-70_332_mi-cable.md
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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.
nfpa-70_334_nm-cable.md
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@@ -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.
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title: Article 422 Appliances
---
# Article 422 Appliances
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title: Article 424 Fixed Electric Space-Heating Equipment
---
# Article 424 Fixed Electric Space-Heating Equipment
nfpa-70_430_motors.md
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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
nfpa-70_440_hvac-equipment.md
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- authorship/other
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- 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.
nfpa-70_450_transformers.md
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@@ -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.
nfpa-70_700_emergency-systems.md
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title: Article 700 Emergency Systems
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- 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
nfpa-70_dump_wiring-methods.md
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nfpa-70_national-electric-code.md
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@@ -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]]
raceway-terms.md
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"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.]]
sleeving-takeoff.md
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@@ -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/).
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---