5.4 KiB
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Article 220 Branch-Circuit, Feeder, and Service Load Calculations |
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.
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(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.
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(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_210_branch-circuits#210.11(C)(1) Small-Appliance Branch Circuits. and nfpa-70_210_branch-circuits#210.11(C)(2) Laundry Branch Circuits..
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.