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For range loads, a special rule in Section 220.18(C) applies, allowing the application of a demand factor on the individual branch circuit that goes to an individual range. For the most part, this is a key difference between the calculations for branch circuits and feeders, that is, demand factors are usually applied only to feeders and service conductors, not to branch circuits.
In general, a branch circuit must be sized for the entire load connected to it, but a feeder may be reduced in size based on how much of the load is actually on at the same time. With a feeder, it is necessary to think about the non-coincident nature of some of the load that exists on the various branch circuits that are connected to it. In the case of ranges, however, it is permitted to apply a demand factor to the total load at the branch circuit. This recognizes that an electric range actually represents a number of smaller loads. The assumption here, based on many years of experience with this type of load, is that a situation where the entire load is on at the same time for any extended period is very unlikely.
© Hughes Associates,Inc. 2012