From 201a38510f3d04d34b06c86fbeb78c88a0cd1992 Mon Sep 17 00:00:00 2001 From: Zane Meyers Date: Fri, 3 Oct 2025 15:08:34 -0400 Subject: [PATCH] vault backup: 2025-10-03 15:08:33 --- .../plugins/recent-files-obsidian/data.json | 48 ++- conductor-sizing.md | 92 +++++- ...quirements-for-electrical-installations.md | 123 ++++++++ nfpa-70_article-210_branch-circuits.md | 293 ++++++++++++++++++ nfpa-70_article-215_feeders.md | 86 +++++ nfpa-70_article-220_load-calculations.md | 154 +++++++++ ...ticle-310_conductors_for_general_wiring.md | 228 ++++++++++++++ voltage-drop.md | 32 -- 8 files changed, 992 insertions(+), 64 deletions(-) create mode 100644 nfpa-70_article-110_requirements-for-electrical-installations.md create mode 100644 nfpa-70_article-210_branch-circuits.md create mode 100644 nfpa-70_article-215_feeders.md create mode 100644 nfpa-70_article-220_load-calculations.md create mode 100644 nfpa-70_article-310_conductors_for_general_wiring.md delete mode 100644 voltage-drop.md diff --git a/.obsidian/plugins/recent-files-obsidian/data.json b/.obsidian/plugins/recent-files-obsidian/data.json index e26211a..eceef70 100644 --- a/.obsidian/plugins/recent-files-obsidian/data.json +++ b/.obsidian/plugins/recent-files-obsidian/data.json @@ -1,13 +1,33 @@ { "recentFiles": [ { - "basename": "voltage-drop", - "path": "voltage-drop.md" + "basename": "conductor-sizing", + "path": "conductor-sizing.md" }, { "basename": "README", "path": "README.md" }, + { + "basename": "nfpa-70_article-210_branch-circuits", + "path": "nfpa-70_article-210_branch-circuits.md" + }, + { + "basename": "nfpa-70_article-215_feeders", + "path": "nfpa-70_article-215_feeders.md" + }, + { + "basename": "nfpa-70_article-220_load-calculations", + "path": "nfpa-70_article-220_load-calculations.md" + }, + { + "basename": "nfpa-70_article-310_conductors_for_general_wiring", + "path": "nfpa-70_article-310_conductors_for_general_wiring.md" + }, + { + "basename": "nfpa-70_article-110_requirements-for-electrical-installations", + "path": "nfpa-70_article-110_requirements-for-electrical-installations.md" + }, { "basename": "idea", "path": "Templates/idea.md" @@ -171,30 +191,6 @@ { "basename": "construction-estimating-software", "path": "construction-estimating-software.md" - }, - { - "basename": "burndy-AYP300_pigtail-adaptor", - "path": "burndy-AYP300_pigtail-adaptor.png" - }, - { - "basename": "estimating-dimensionality", - "path": "estimating-dimensionality.md" - }, - { - "basename": "estimating-detail", - "path": "estimating-detail.md" - }, - { - "basename": "estimating-culture", - "path": "estimating-culture.md" - }, - { - "basename": "estimating-as-code", - "path": "estimating-as-code.md" - }, - { - "basename": "breakdown-objects", - "path": "breakdown-objects.md" } ], "omittedPaths": [], diff --git a/conductor-sizing.md b/conductor-sizing.md index 7d6b35d..4499ee2 100644 --- a/conductor-sizing.md +++ b/conductor-sizing.md @@ -3,10 +3,56 @@ id: aliases: [] tags: - destiny/fleeting + - status/incomplete - topic/electrical - type/encyclopedia --- -# Feeder Sizing +# Conductor Sizing + +## "The 80% Rule" + +"The 80% Rule" is a rule of thumb +referring to a common convention of several articles +including: + +- [[nfpa-70_article-210_branch-circuits#210.19(A)(1) General.]] +- [[nfpa-70_article-215_feeders#215.2(A)(1) General.]] + +which paraphrased states: + +> ... the minimum conductor size shall have an ampacity +> not less than the noncontinuous load +> plus 125 percent of the continuous load + +When the rule is repeated, +the noncontinuous load is ignored +and it is stated that conductors are suitable +for 80% their listed rating, +since 80% is the reciprocal of 125%. + +## Branch Circuits + +### Receptacle Branch + +> [!important] +> There is no maximum number of receptacles per circuit _in any occupancy_. + +It is a common misconception that the limit +can be calculated with a formula like + +$$ +\frac{1.25(180VA)}{120V} = 1.875A, \quad \frac{20A}{1.875A} = 10.\bar{6} +$$ + +but the 180VA per yoke load specified in +[[nfpa-70_article-220_load-calculations#220.14(I) Receptacle Outlets.|220.14(I)]] +is specifically for calculating service and feeder sizing. + +Per [[nfpa-70_article-210_branch-circuits#210.19(A)(1) General.|210.19(A)(1)]] +a receptacle branch circuit's load +is the load of the equipment intended to be served by it. + +## Feeders > [!cite] 250.122 Size of Equipment Grounding Conductors > **(A) General.** Copper, aluminum, or copper-clad aluminum @@ -37,15 +83,49 @@ Given a minimum ampacity, find all valid configurations. Rank by total cost of install. -## Complexity to Ignore +### Complexity to Ignore -### Conductor Material +#### Conductor Material Tinned copper and copper-clad aluminum conductors can be assumed out of scope. -## Complexity to Respect +### Complexity to Respect + +#### Equipment Grounding Conductor Material Wire and EGC conductors are usually assumed to match, -but it is sometimes preferable to use a copper EGC -with high-amp aluminum parallel feeds. +but it is sometimes necessary to use a copper EGC with aluminum wires, +either for spec requirements or conduit fill considerations. + +## Voltage Drop + +$$ +V_d = \frac{ I \times R \times L \times M }{ P } +$$ + +where +- $V_d$ = Voltage Drop in volts ($V$) +- $I$ = Current in Amperes ($A$) +- $R$ = Linear resistance in ohms per foot ($\Omega\text{ft}^{-1}$) +- $L$ = Length of wire one way in feet ($\text{ft}$) +- $M$ = Multiplier + - $2$ for 1-phase + - $\sqrt{3}$ for 3-phase +- $P$ = Number of parallel runs + +It is often more useful to know the maximum length +a certain wiring configuration is suitable for. + +$$ +L = \frac{ V_d }{ I \times M } \times \frac{ P }{ R } +$$ + +- $L$ = Max length of wire one way in feet ($\text{ft}$) +- $\frac{ V_d }{ I \times M }$ = Max circuit resistance in ohms ($\Omega$) +- $\frac{ P }{ R }$ = ??? in feet per ohm ($\text{ft}\Omega^{-1}$) + +> [!info] Ohm's Law +> $$ +> V = I \times R, \quad R = \frac{ V }{ I }, \quad I = \frac{ V }{ R } +> $$ diff --git a/nfpa-70_article-110_requirements-for-electrical-installations.md b/nfpa-70_article-110_requirements-for-electrical-installations.md new file mode 100644 index 0000000..bfb5de0 --- /dev/null +++ b/nfpa-70_article-110_requirements-for-electrical-installations.md @@ -0,0 +1,123 @@ +--- +id: +aliases: + - nec-110 +tags: + - authorship/other + - destiny/uncertain + - status/incomplete + - topic/electrical + - type/encyclopedia +--- +# Article 110 Requirements for Electrical Installations + +## Part I. General + +### 110.1 Scope. + +This article covers general requirements +for the examination and approval, installation and use, +access to and spaces about electrical conductors and equipment; +enclosures intended for personnel entry; +and tunnel installations. + +> [!info] Informational Note: +> See Informative Annex J for information regarding ADA accessibility design. + + + +### 110.14 Electrical Connections. + +Because of different characteristics of dissimilar metals, +devices such as pressure terminal +or pressure splicing connectors and soldering lugs +shall be identified for the material of the conductor +and shall be properly installed and used. +Conductors of dissimilar metals +shall not be intermixed in a terminal or splicing connector +where physical contact occurs between dissimilar conductors +(such as copper and aluminum or aluminum and copper-clad aluminum), +unless the device is identified for the purpose and conditions of use. +Materials such as solder, fluxes, inhibitors, and compounds, +where employed, shall be suitable for the use +and shall be of a type that will not adversely affect +the conductors, installation, or equipment. +Connectors and terminals for conductors more finely stranded +than Class B and Class C stranding as shown in Chapter 9, Table 10, +shall be identified for the specific conductor class or classes. + +#### 110.14(C) Temperature Limitations. + +The temperature rating associated with the ampacity of a conductor +shall be selected and coordinated so as not to exceed the lowest +temperature rating of any connected termination, conductor, or device. +Conductors with temperature ratings higher than specified for +terminations shall be permitted to be used +for ampacity adjustment, correction, or both. + +##### 110.14(C)(1) Equipment Provisions. + +The determination of termination provisions of equipment +shall be based on 110.14(C)(1)(a) or (C)(1)(b). +Unless the equipment is listed and marked otherwise, +conductor ampacities used in determining equipment termination provisions +shall be based on Table 310.16 as appropriately modified by 310.12. + +* (a) Termination provisions of equipment for circuits rated 100 amperes or less, + or marked for 14 AWG through 1 AWG conductors, + shall be used only for one of the following: + * (1) Conductors rated 60°C (140°F). + * (2) Conductors with higher temperature ratings, + provided the ampacity of such conductors + is determined based on the 60°C (140°F) ampacity of the conductor size used. + * (3) Conductors with higher temperature ratings + if the equipment is listed and identified for use with such conductors. + * (4) For motors marked with design letters B, C, or D, + conductors having an insulation rating of 75°C (167°F) or higher + shall be permitted to be used, + provided the ampacity of such conductors + does not exceed the 75°C (167°F) ampacity. + +* (b) Termination provisions of equipment + for circuits rated over 100 amperes, + or marked for conductors larger than 1 AWG, + shall be used only for one of the following: + * (1) Conductors rated 75°C (167°F) + * (2) Conductors with higher temperature ratings, + provided the ampacity of such conductors + does not exceed the 75°C (167°F) ampacity of the conductor size used, + or up to their ampacity if the equipment is listed and identified + for use with such conductors + +##### 110.14(C)(2) Separate Connector Provisions. + +Separately installed pressure connectors shall be used with conductors at the ampacities not exceeding the ampacity at the listed and identified temperature rating of the connector. + +Informational Note: +With respect to 110.14(C)(1) and (C)(2), +equipment markings or listing information may additionally restrict +the sizing and temperature ratings of connected conductors. + +#### 110.14(D) Terminal Connection Torque. + +Tightening torque values for terminal connections +shall be as indicated on equipment +or in installation instructions provided by the manufacturer. +An approved means shall be used to achieve the indicated torque value. + +Informational Note No. 1: +Examples of approved means of achieving the indicated torque values +include torque tools or devices such as shear bolts +or breakaway-style devices with visual indicators +that demonstrate that the proper torque has been applied. + +Informational Note No. 2: +The equipment manufacturer can be contacted +if numeric torque values are not indicated on the equipment +or if the installation instructions are not available. +Informative Annex I of UL Standard 486A-486B, Standard for Safety-Wire Connectors, +provides torque values in the absence of manufacturer's recommendations. + +Informational Note No. 3: +Additional information for torquing threaded connections and terminations +can be found in Section 8.11 of NFPA 70B-2019, Recommended Practice for Electrical Equipment Maintenance. diff --git a/nfpa-70_article-210_branch-circuits.md b/nfpa-70_article-210_branch-circuits.md new file mode 100644 index 0000000..577c58d --- /dev/null +++ b/nfpa-70_article-210_branch-circuits.md @@ -0,0 +1,293 @@ +--- +id: +aliases: + - nec-210 +tags: + - authorship/other + - destiny/uncertain + - status/incomplete + - topic/electrical + - type/encyclopedia +--- +# NEC Article 210 Branch Circuits + +## Part I. General Provisions + +### 210.1 Scope. + +This article provides the general requirements for branch circuits. + + + +### 210.11 Branch Circuits Required. + +Branch circuits for lighting and for appliances, +including motor-operated appliances, +shall be provided to supply the loads calculated in accordance with 220.10. +In addition, branch circuits shall be provided for specific loads not covered by 220.10 +where required elsewhere in this Code +and for dwelling unit loads as specified in 210.11(C). + +#### 210.11(A) Number of Branch Circuits. + +The minimum number of branch circuits +shall be determined from the total calculated load +and the size or rating of the circuits used. +In all installations, the number of circuits +shall be sufficient to supply the load served. +In no case shall the load on any circuit exceed the maximum specified by 220.18. + +#### 210.11(B) Load Evenly Proportioned Among Branch Circuits. + +Where the load is calculated on the basis of volt-amperes per square meter or per square foot, +the wiring system up to and including the branch-circuit panelboard(s) +shall be provided to serve not less than the calculated load. +This load shall be evenly proportioned +among multioutlet branch circuits within the panelboard(s). +Branch-circuit overcurrent devices and circuits +shall be required to be installed only to serve the connected load. + +#### 210.11(C) Dwelling Units. + +##### 210.11(C)(1) Small-Appliance Branch Circuits. + +In addition to the number of branch circuits required by other parts of this section, +two or more 20-ampere small-appliance branch circuits shall be provided +for all receptacle outlets specified by 210.52(B). + +##### 210.11(C)(2) Laundry Branch Circuits. + +In addition to the number of branch circuits required by other parts of this section, +at least one additional 20-ampere branch circuit shall be provided +to supply the laundry receptacle outlet(s) required by 210.52(F). +This circuit shall have no other outlets. + +##### 210.11(C)(3) Bathroom Branch Circuits. + +In addition to the number of branch circuits required by other parts of this section, +one or more 120-volt, 20-ampere branch circuit shall be provided +to supply bathroom(s) receptacle outlet(s) required by 210.52(D) +and any countertop and similar work surface receptacle outlets. +Such circuits shall have no other outlets. + +Exception: +Where the 20-ampere circuit supplies a single bathroom, +outlets for other equipment within the same bathroom +shall be permitted to be supplied in accordance with 210.23(A)(1) and (A)(2). + +##### 210.11(C)(4) Garage Branch Circuits. + +In addition to the number of branch circuits required by other parts of this section, +at least one 120-volt, 20-ampere branch circuit shall be installed +to supply receptacle outlets required by 210.52(G)(1) +for attached garages and in detached garages with electric power. +This circuit shall have no other outlets. + +Exception: +This circuit shall be permitted to supply +readily accessible outdoor receptacle outlets. + + + +## Part II. Branch-Circuit Ratings + +### 210.18 Rating. + +Branch circuits recognized by this article +shall be rated in accordance with the maximum permitted ampere rating +or setting of the overcurrent device. +The rating for other than individual branch circuits +shall be 15, 20, 30, 40, and 50 amperes. +Where conductors of higher ampacity are used for any reason, +the ampere rating or setting of the specified overcurrent device +shall determine the circuit rating. + +> [!important] Exception: +> Multioutlet branch circuits greater than 50 amperes +> shall be permitted to supply nonlighting outlet loads on industrial premises +> where conditions of maintenance and supervision ensure +> that only qualified persons service the equipment. + +### 210.19 Conductors -- Minimum Ampacity and Size. + + + +#### 210.19(A) Branch Circuits Not More Than 600 Volts. + +##### 210.19(A)(1) General. + +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_article-110_requirements-for-electrical-installations#110.14(C) Temperature Limitations.|110.14(C)]] +for equipment terminations. + +* (a) Where a branch circuit supplies continuous loads + or any combination of continuous and noncontinuous loads, + the minimum branch-circuit conductor size + shall have an ampacity not less than the noncontinuous load + plus 125 percent of the continuous load in accordance with + [[nfpa-70_article-310_conductors_for_general_wiring#310.14 Ampacities for Conductors Rated 0 Volts – 2000 Volts.|310.14]]. + +* (b) The minimum branch-circuit conductor size + shall have an ampacity not less than the maximum load to be served + after the application of any adjustment + or correction factors in accordance with + [[nfpa-70_article-310_conductors_for_general_wiring#310.15 Ampacity Tables.|310.15]]. + +##### 210.19(A)(2) Branch Circuits with More than One Receptacle. + +Conductors of branch circuits supplying more than one receptacle +for cord-and-plug-connected portable loads +shall have an ampacity of not less than the rating of the branch circuit. + + + +### 210.21 Outlet Devices. + +Outlet devices shall have an ampere rating +that is not less than the load to be served +and shall comply with 210.21(A) and (B). + +#### 210.21(A) Lampholders. + +Where connected to a branch circuit having a rating in excess of 20 amperes, lampholders +shall be of the heavy-duty type. A heavy-duty lampholder +shall have a rating of not less than 660 watts if of the admedium type, +or not less than 750 watts if of any other type. + +#### 210.21(B) Receptacles. + +##### 210.21(B)(1) Single Receptacle on an Individual Branch Circuit. + +A single receptacle installed on an individual branch circuit +shall have an ampere rating +not less than that of the branch circuit. + +> [!important] Exception No. 1: +> A receptacle installed in accordance with 430.81(B). + +> [!important] Exception No. 2: +> A receptacle installed exclusively for the use of a cord-and-plug-connected arc welder +> shall be permitted to have an ampere rating +> not less than the minimum branch-circuit conductor ampacity +> determined by 630.11(A) for arc welders. + +> [!info] Informational Note: +> See the definition of receptacle in Article 100. + +##### 210.21(B)(2) Total Cord-and-Plug-Connected Load. + +Where connected to a branch circuit supplying two or more receptacles or outlets, +a receptacle shall not supply a total cord-and-plug-connected load +in excess of the maximum specified in Table 210.21(B)(2). + +##### Table 210.21(B)(2) Maximum Cord-and-Plug-Connected Load to Receptacle + +| Circuit Rating (Amperes) | Receptacle Rating (Amperes) | Maximum Load (Amperes) | +| ------------------------ | --------------------------- | ---------------------- | +| 15 or 20 | 15 | 12 | +| 20 | 20 | 16 | +| 30 | 30 | 24 | + +##### 210.21(B)(3) Receptacle Ratings. + +Where connected to a branch circuit supplying two or more receptacles or outlets, +receptacle ratings shall conform to the values listed in Table 210.21(B)(3), +or, where rated higher than 50 amperes, +the receptacle rating shall not be less than the branch-circuit rating. + +> [!important] Exception No. 1: +> Receptacles installed exclusively +> for the use of one or more cord-and-plug-connected arc welders +> shall be permitted to have ampere ratings +> not less than the minimum branch-circuit conductor ampacity +> determined by 630.11(A) or (B) for arc welders. + +> [!important] Exception No. 2: +> The ampere rating of a receptacle +> installed for electric discharge lighting +> shall be permitted to be based on 410.62(C). + +##### Table 210.21(B)(3) Receptacle Ratings for Various Size Circuits + +| Circuit Rating (Amperes) | Receptacle Rating (Amperes) | +| ------------------------ | --------------------------- | +| 15 | Not over 15 | +| 20 | 15 or 20 | +| 30 | 30 | +| 40 | 40 or 50 | +| 50 | 50 | + +##### 210.21(B)(4) Range Receptacle Rating. + +The ampere rating of a range receptacle +shall be permitted to be based on a single range demand load +as specified in Table 220.55. + +### 210.22 Permissible Loads, Individual Branch Circuits. + +An individual branch circuit +shall be permitted to supply any load for which it is rated, +but in no case shall the load exceed the branch-circuit ampere rating. + +### 210.23 Permissible Loads, Multiple-Outlet Branch Circuits. + +In no case shall the load exceed the branch-circuit ampere rating. +A branch circuit supplying two or more outlets or receptacles +shall supply only the loads specified according to its size +as specified in 210.23(A) through (D) +and as summarized in 210.24 and Table 210.24. + +#### 210.23(A) 15- and 20-Ampere Branch Circuits. + +A 15- or 20-ampere branch circuit +shall be permitted to supply lighting units +or other utilization equipment, +or a combination of both, +and shall comply with 210.23(A)(1) and (A)(2). + +> [!important] Exception: +> The small-appliance branch circuits, +> laundry branch circuits, and bathroom branch circuits +> required in a dwelling unit(s) by 210.11(C)(1), (C)(2), and (C)(3) +> shall supply only the receptacle outlets specified in that section. + +##### 210.23(A)(1) Cord-and-Plug-Connected Equipment Not Fastened in Place. + +The rating of any one cord-and-plug-connected utilization equipment not fastened in place +shall not exceed 80 percent of the branch-circuit ampere rating. + +##### 210.23(A)(2) Utilization Equipment Fastened in Place. + +The total rating of utilization equipment fastened in place, other than luminaires, +shall not exceed 50 percent of the branch-circuit ampere rating +where lighting units, cord-and-plug-connected utilization equipment not fastened in place, +or both, are also supplied. + +#### 210.23(B) 30-Ampere Branch Circuits. + +A 30-ampere branch circuit +shall be permitted to supply fixed lighting units +with heavy-duty lampholders in other than a dwelling unit(s) +or utilization equipment in any occupancy. +A rating of any one cord-and-plug-connected utilization equipment +shall not exceed 80 percent of the branch-circuit ampere rating. + +##### 210.23(C) 40and 50-Ampere Branch Circuits. + +A 40- or 50-ampere branch circuit +shall be permitted to supply cooking appliances +that are fastened in place in any occupancy. +In other than dwelling units, +such circuits shall be permitted to supply +fixed lighting units with heavy-duty lampholders, +infrared heating units, +or other utilization equipment. + +#### 210.23(D) Branch Circuits Larger Than 50 Amperes. + +Branch circuits larger than 50 amperes +shall supply only nonlighting outlet loads. + + diff --git a/nfpa-70_article-215_feeders.md b/nfpa-70_article-215_feeders.md new file mode 100644 index 0000000..04dc55a --- /dev/null +++ b/nfpa-70_article-215_feeders.md @@ -0,0 +1,86 @@ +--- +id: +aliases: + - nec-215 +tags: + - authorship/other + - destiny/uncertain + - status/incomplete + - topic/electrical + - type/encyclopedia +--- +# Article 215 Feeders + +## 215.1 Scope. + +This article covers the installation requirements, overcurrent protection requirements, minimum size, and ampacity of conductors for +feeders. + +Exception: +Feeders for electrolytic cells as covered in 668.3(C)(1) and (C)(4). + +#### 215.2 Minimum Rating and Size. + +#### 215.2(A) Feeders Not More Than 1000 Volts. + +#### 215.2(A)(1) General. + +Feeder conductors shall have an ampacity +not less than the larger of 215.2(A)(1)(a) or (A)(1)(b) +and shall comply with 110.14(C). + +- (a) Where a feeder supplies continuous loads + or any combination of continuous and noncontinuous loads, + the minimum feeder conductor size shall have an ampacity + not less than the noncontinuous load plus 125 percent of the continuous 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 + in accordance with + [[nfpa-70_article-310_conductors_for_general_wiring#310.14 Ampacities for Conductors Rated 0 Volts – 2000 Volts.|310.14]]. + +Exception No. 1: +If the assembly, including the overcurrent devices protecting the feeder(s), +is listed for operation at 100 percent of its rating, +the ampacity of the feeder conductors shall be permitted to be not less +than the sum of the continuous load plus the noncontinuous load. + +Exception No. 2: +Where a portion of a feeder is connected at both its supply and load ends +to separately installed pressure connections as covered in 110.14(C)(2), +it shall be permitted to have an ampacity +not less than the sum of the continuous load plus the noncontinuous load. +No portion of a feeder installed under this exception +shall extend into an enclosure containing either the feeder supply +or the feeder load terminations, as covered in 110.14(C)(1). + +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. + +Informational Note No. 1: +See Examples D1 through D11 in Informative Annex D. + +Informational Note No. 2: +Conductors for feeders, as defined in Article 100, +sized to prevent a voltage drop exceeding 3 percent +at the farthest outlet of power, heating, and lighting loads, +or combinations of such loads, +and where the maximum total voltage drop on both feeders and branch circuits +to the farthest outlet does not exceed 5 percent, +will provide reasonable efficiency of operation. + +Informational Note No. 3: +See 210.19(A), Informational Note No. 4, for voltage drop for branch circuits. + +#### 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. + +Additional minimum sizes shall be as specified in 215.2(A)(3) +under the conditions stipulated. diff --git a/nfpa-70_article-220_load-calculations.md b/nfpa-70_article-220_load-calculations.md new file mode 100644 index 0000000..ba19483 --- /dev/null +++ b/nfpa-70_article-220_load-calculations.md @@ -0,0 +1,154 @@ +--- +id: +aliases: + - nec-220 +tags: + - authorship/other + - destiny/uncertain + - status/incomplete + - topic/electrical + - type/encyclopedia +--- +# Article 220 Branch-Circuit, Feeder, and Service Load Calculations + +## Part I. General + +### 220.1 Scope. + +This article provides requirements +for calculating branch-circuit, feeder, and service loads. +Part I provides general requirements for calculation methods. +Part II provides calculation methods for branch-circuit loads. +Parts III and IV provide calculation methods for feeder and service loads. +Part V provides calculation methods for farm loads. + +Informational Note No. 1: +See examples in Informative Annex D. + +Informational Note No. 2: +See Figure 220.1 for information on the organization of Article 220. + +### Figure 220.1 Branch-Circuit, Feeder, and Service Load Calculation Methods. + + + + + +### 220.14 Other Loads -- All Occupancies. + +In all occupancies, the minimum load for each outlet +for general-use receptacles and outlets not used for general illumination +shall not be less than that calculated in 220.14(A) through (M), +the loads shown being based on nominal branch-circuit voltages. + +Exception: +The loads of outlets serving switchboards and switching frames in telephone exchanges +shall be waived from the calculations. + + + +#### 220.14(A) Specific Appliances or Loads. + +An outlet for a specific appliance +or other load not covered in 220.14(B) through (M) +shall be calculated based on the ampere rating +of the appliance or load served. + +#### 220.14(B) Electric Dryers and Electric Cooking Appliances in Dwellings and Household Cooking Appliances Used in Instructional Programs. + +Load calculations shall be permitted +as specified in 220.54 for electric dryers +and in 220.55 for electric ranges and other cooking appliances. + +#### 220.14(C) Motor Outlets. + +Loads for motor outlets shall be calculated +in accordance with the requirements in 430.22, 430.24, and 440.6. + +#### 220.14(D) Luminaires. + +An outlet supplying luminaire(s) shall be calculated +based on the maximum volt-ampere rating of the equipment +and lamps for which the luminaire(s) is rated. + +#### 220.14(E) Heavy-Duty Lampholders. + +Outlets for heavy-duty lampholders +shall be calculated at a minimum of 600 volt-amperes. + +#### 220.14(F) Sign and Outline Lighting. + +Sign and outline lighting outlets +shall be calculated at a minimum of 1200 volt-amperes +for each required branch circuit specified in 600.5(A). + +#### 220.14(G) Show Windows. + +Show windows shall be calculated +in accordance with either of the following: + +- (1) The unit load per outlet as required in other provisions of this section +- (2) At 200 volt-amperes per linear 300 mm (1 ft) of show window + +#### 220.14(H) Fixed Multioutlet Assemblies. + +Fixed multioutlet assemblies used in other than dwelling units +or the guest rooms or guest suites of hotels or motels +shall be calculated in accordance with (H)(1) or (H)(2). +For the purposes of this section, +the calculation shall be permitted +to be based on the portion that contains receptacle outlets. + +- (1) Where appliances are unlikely to be used simultaneously, + each 1.5 m (5 ft) or fraction thereof + of each separate and continuous length + shall be considered as one outlet of not less than 180 volt-amperes. + +- (2) Where appliances are likely to be used simultaneously, + each 300 mm (1 ft) or fraction thereof + shall be considered as an outlet of not less than 180 volt-amperes. + +#### 220.14(I) Receptacle Outlets. + +Except as covered in 220.14(J) and (K), +receptacle outlets shall be calculated at not less than 180 volt-amperes +for each single or for each multiple receptacle on one yoke. +A single piece of equipment consisting of a multiple receptacle +comprised of four or more receptacles +shall be calculated at not less than 90 volt-amperes per receptacle. +This provision shall not be applicable to the receptacle outlets +specified in [[nfpa-70_article-210_branch-circuits#210.11(C)(1) Small-Appliance Branch Circuits.|210.11(C)(1)]] +and [[nfpa-70_article-210_branch-circuits#210.11(C)(2) Laundry Branch Circuits.|(C)(2)]]. + +#### 220.14(J) Dwelling Units. + +In one-family, two-family, and multifamily dwellings, +the minimum unit load shall be not less than 33 volt-amperes/m$^2$ (3 volt-amperes/ft$^2$). +The lighting and receptacle outlets specified in 220.14(J)(1), (J)(2), and (J)(3) +are included in the minimum unit load. +No additional load calculations shall be required for such outlets. +The minimum lighting load shall be determined using the minimum unit load +and the floor area as determined in 220.11 for dwelling occupancies. +Motors rated less than 1⁄8 hp and connected to a lighting circuit +shall be considered part of the minimum lighting load. + +- (1) All general-use receptacle outlets of 20-ampere rating or less, + including receptacles connected to the circuits in 210.11(C)(3) and 210.11(C)(4) +- (2) The receptacle outlets specified in 210.52(E) and (G) +- (3) The lighting outlets specified in 210.70 + +#### 220.14(K) Office Buildings. + +In office buildings, the receptacle loads +shall be calculated to be the larger of (1) or (2): + +- (1) The calculated load from 220.14(I) + after all demand factors have been applied +- (2) 11 volt-amperes/m$^2$ or 1 volt-ampere/ft$^2$ + +#### 220.14(L) Other Outlets. + +Other outlets not covered in 220.14(A) through (K) +shall be calculated based on 180 volt-amperes per outlet. + + diff --git a/nfpa-70_article-310_conductors_for_general_wiring.md b/nfpa-70_article-310_conductors_for_general_wiring.md new file mode 100644 index 0000000..79df557 --- /dev/null +++ b/nfpa-70_article-310_conductors_for_general_wiring.md @@ -0,0 +1,228 @@ +--- +id: +aliases: + - nec-310 +tags: + - authorship/other + - destiny/uncertain + - status/incomplete + - topic/electrical + - type/encyclopedia +--- +# Article 310 Conductors for General Wiring + +## Part I. General + +#### 310.1 Scope. + +This article covers general requirements for conductors +rated up to and including 2000 volts +and their type designations, insulations, markings, +mechanical strengths, ampacity ratings, and uses. +These requirements do not apply to conductors that form an integral part of equipment, +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. + + + +## 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)]]. + +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(B) Thickness of Insulation for Nonshielded Types RHH and RHW Solid Dielectric Insulated Conductors Rated 2000 Volts + + + + + +## Part III. Installation + +### 310.10 Uses Permitted. + +The conductors described in [[#310.4 Conductor Constructions and Applications.|310.4]] +shall be permitted for use in any of the wiring methods covered in Chapter 3 +and as specified in their respective tables +or as permitted elsewhere in this Code. + + + +### 310.14 Ampacities for Conductors Rated 0 Volts – 2000 Volts. + +#### 310.14(A) General. + +##### 310.14(A)(1) Tables or Engineering Supervision. + +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. + + + +### 310.15 Ampacity Tables. + +#### 310.15(A) General. + +Ampacities for conductors rated 0 volts to 2000 volts +shall be as specified in the Ampacity Table 310.16 through Table 310.21, +as modified by 310.15(A) through (F) and 310.12. +Under engineering supervision, +ampacities of sizes not shown in ampacity tables +for conductors meeting the general wiring requirements +shall be permitted to be determined by interpolation of the adjacent conductors +based on the conductor's area. +The temperature correction and adjustment factors +shall be permitted to be applied to the ampacity +for the temperature rating of the conductor, +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: + +* (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. + + + +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). + +#### 310.15(B) Ambient Temperature Correction Factors. + +##### 310.15(B)(1) General. + +Ampacities for ambient temperatures +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). + + + +$$ +I\prime = I \sqrt{\frac{ T_c -T_{a}\prime }{ T_c - T_a }} +$$ + +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) +* $T_a$ = 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.), +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. + +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) + +For ambient temperatures other than 30°C (86°F), +multiply the ampacities specified in the ampacity tables +by the appropriate correction factor shown below. + + + +##### Table 310.15(B)(2) Ambient Temperature Correction Factors Based on 40°C (104°F) + +For ambient temperatures other than 40°C (104°F), +multiply the ampacities specified in the ampacity tables +by the appropriate correction factor shown below. + + + +#### 310.15(C) Adjustment Factors. + +##### 310.15(C)(1) More than Three Current-Carrying Conductors. + +The ampacity of each conductor shall be reduced as shown in Table 310.15(C)(1) +where the number of current-carrying conductors in a raceway or cable exceeds three, +or where single conductors or multiconductor cables not installed in raceways +are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.). +Each current-carrying conductor of a paralleled set of conductors +shall be counted as a current-carrying conductor. + + + +##### Table 310.15(C)(1) Adjustment Factors for More Than Three Current-Carrying Conductors + +| Number of Conductors* | Percent of Values in Table 310.16 Through Table 310.19 as Adjusted for Ambient Temperature if Necessary | +| --------------------- | ------------------------------------------------------------------------------------------------------- | +| 4–6 | 80 | +| 7–9 | 70 | +| 10–20 | 50 | +| 21–30 | 45 | +| 31–40 | 40 | +| 41 and above | 35 | + +\*Number of conductors is the total number of conductors in the raceway or cable, +including spare conductors. +The count shall be adjusted in accordance with 310.15(E) and (F). +The count shall not include conductors +that are connected to electrical components +that cannot be simultaneously energized. + +##### 310.15(C)(2) Raceway Spacing. + +Spacing between raceways shall be maintained. + +#### 310.15(D) Bare or Covered Conductors. + +Where bare or covered conductors are installed with insulated conductors, +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. + + diff --git a/voltage-drop.md b/voltage-drop.md deleted file mode 100644 index d4df287..0000000 --- a/voltage-drop.md +++ /dev/null @@ -1,32 +0,0 @@ ---- -id: -aliases: [] -tags: - - destiny/fleeting - - type/idea ---- -# Voltage Drop - -> [!info] Ohm's Law -> $$ -> V = I \times R \quad R = \frac{ V }{ I } -> $$ - -$$ -Vd = \frac{ I \times R \times L \times M }{ P } -$$ - -$$ -L = \frac{ Vd }{ I \times M } \times \frac{ P }{ R } -$$ - -where - -- $Vd$ = Maximum Voltage Drop in volts -- $I$ = Current in Amps -- $R$ = Resistance in ohms per foot -- $L$ = Length of wire one way in feet -- $M$ = Multiplier - - $2$ for 1-phase - - $\sqrt{3}$ for 3-phase -- $P$ = Number of parallel runs