Article 220 Branch-Circuit, Feeder, and Service Calculations
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.
Table 220.3 Additional Load Calculation References
|Calculation||Article||Section (or Part)|
|Air-conditioning and refrigerating equipment, branch-circuit conductor sizing||440||Part IV|
|Cranes and hoists, rating and size of conductors||610||610.14|
|Electric vehicle charging system branch-circuit and feeder calculations||625||625.41|
|Electric welders, ampacity calculations||630||630.11, 630.31|
|Electrically driven or controlled irrigation machines||675||675.7(A), 675.22(A)|
|Electrified truck parking space||626|
|Electrolytic cell lines||668||668.3(C)|
|Electroplating, branch-circuit conductor sizing||669||669.5|
|Elevator feeder demand factors||620||620.14|
|Fire pumps, voltage drop (mandatory calculation)||695||695.7|
|Fixed electric heating equipment for pipelines and vessels, branch-circuit sizing||427||427.4|
|Fixed electric space-heating equipment, branch-circuit sizing||424||424.3|
|Fixed outdoor electric deicing and snow-melting equipment, branch-circuit sizing||426||426.4|
|Industrial machinery, supply conductor sizing||670||670.4(A)|
|Marinas and boatyards, feeder and service load calculations||555||555.12|
|Mobile homes, manufactured homes, and mobile home parks, total load for determining power supply||550||550.18(B)|
|Mobile homes, manufactured homes, and mobile home parks, allowable demand factors for park electrical wiring systems||550||550.31|
|Motion picture and television studios and similar locations - sizing of feeder conductors for television studio sets||530||530.19|
|Motors, feeder demand factor||430||430.26|
|Motors, multimotor and combination-load equipment||430||430.25|
|Motors, several motors or a motor(s) and other load(s)||430||430.24|
|Over 600-volt branch-circuit calculations||210||210.19(B)|
|Over 600-volt feeder calculations||215||215.2(B)|
|Phase converters, conductors||455||455.6|
|Recreational vehicle parks, basis of calculations||551||551.73(A)|
|Sensitive electrical equipment, voltage drop (mandatory calculation)||647||647.4(D)|
|Solar photovoltaic systems, circuit sizing and current||690||690.8|
|Storage-type water heaters||422||422.11(E)|
|Theaters, stage switchboard feeders||520||520.27|
Informational Note: The unit values herein are based on minimum load conditions and 100 percent power factor and may not provide sufficient capacity for the installation contemplated.
Exception: Where the building is designed and constructed to comply with an energy code adopted by the local authority, the lighting load shall be permitted to be calculated at the values specified in the energy code where the following conditions are met:
- A power monitoring system is installed that will provide continuous information regarding the total general lighting load of the building.
- The power monitoring system will be set with alarm values to alert the building owner or manager if the lighting load exceeds the values set by the energy code.
- The demand factors specified in 220.42 are not applied to the general lighting load.
Table 220.12 General Lighting Loads by Occupancy
|Type of Occupancy||Unit Load|
|Volt-Amperes/Square Meter||Volt-Amperes/Square Foot|
|Armories and auditoriums||11||1|
|Barber shops and beauty parlors||33||3|
|Garages — commercial (storage)||6||1/2|
|Hotels and motels, including apartment houses without provision for cooking by tenantsa||22||2|
|Industrial commercial (loft) buildings||22||2|
|In any of the preceding occupancies except one-family dwellings and individual dwelling units of two-family and multifamily dwellings:|
|Assembly halls and auditoriums||11||1|
|Halls, corridors, closets, stairways||6||1/2|
(B) Electric Dryers and Electric Cooking Appliances in Dwellings and Household Cooking Appliances Used in Instructional Programs
- 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.
- 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.
- Loads for structural additions to an existing dwelling unit or for a previously unwired portion of an existing dwelling unit, either of which exceeds 46.5 m2 (500 ft2), shall be calculated in accordance with 220.12 and 220.14.
- Loads for new circuits or extended circuits in previously wired dwelling units shall be calculated in accordance with either 220.12 or 220.14, as applicable.
Informational Note: See Examples D1(a) through D10 in Informative Annex D. See 220.18(B) for the maximum load in amperes permitted for lighting units operating at less than 100 percent power factor.
|Type of Occupancy||Portion of Lighting Load to Which Demand Factor Applies (Volt-Amperes)||Demand Factor (%)|
|Dwelling units||First 3000 or less at||100|
|From 3001 to 120,000 at||35|
|Remainder over 120,000 at||25|
|Hospitals*||First 50,000 or less at||40|
|Remainder over 50,000 at||20|
|Hotels and motels, including apartment houses without provision for cooking by tenants*||First 20,000 or less at||50|
|Front 20,001 to 100.000 at||40|
|Remainder over 100,000 at||30|
|Warehouses (storage)||First 12,500 or less at||100|
|Remainder over 12,500 at||50|
|All others||Total volt-amperes||100|
*The demand factors of this table shall not apply to the calculated load of feeders or services supplying areas in hospitals, hotels, and motels where the entire lighting is likely to be used at one time, as in operating rooms, ballrooms, or dining rooms.
Exception: If the track lighting is supplied through a device that limits the current to the track, the load shall be permitted to be calculated based on the rating of the device used to limit the current.
|Portion of Receptacle Load to Which Demand Factor Applies (Volt-Amperes)||Demand Factor (%)|
|First 10 kVA or less at||100|
|Remainder over 10 kVA at||50|