DEMAND FACTORS

All the loads in a dwelling are not used at the same time, especially for any extended period of time. The NEC^R allows you to apply demand factors to appliances and general lighting loads to compensate for this fact. As a result of these reduced-demand loads, serviceentrance conductors can be sized smaller, allowing the use of smaller branch circuit conductors and circuit breakers. This results in lower material costs.

General Lighting and Receptacle Loads

A demand factor may be applied to general lighting and receptacle loads following table 3-2 (NEC^R, table 220-11). The following example

Table 3-2.\Lighting Load Feeder Demand Factors

Portion of Lighting Load ^Demand

*The demand factors of this table shall not apply to the computed load of feeders to 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.

Reprinted with permission from NPFA 70-1990, the National Electrical Code^R, Copyright^c1989, National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association, on the referenced subject which is represented only by the standard in its entirety.

This demand factor can be applied only when you are performing the calculations for the serviceentrance conductor size.

Fixed Appliance Loads

A 75-percent demand factor may be applied if there are four or more fixed appliances on a branch circuit. The wattage or VA rating taken from the appliance nameplate must be used when this calculation is made. The nameplate full-load rating must be used if three or fewer appliances are connected to a branch circuit.

NOTE: This demand factor does not apply to ranges, clothes dryers, air conditioners, or space-heating units. The demand loads for these appliances are calculated individually.