Question on load calculations for a large house with several feeders coming from a 600 amp MDP. NEC part III 220 gives feeder and service calculations. I understand the demand factors given in NEC part III 220 are allowed to be applied to the all feeders as stated in 220.40. The engineer is saying the demand factors are for service or if there is only one feeder for the residence. Plainly the optional calculation is allowed only if there is one feeder for dwelling as is 310.15(7). I read that the “standard” calculation and its allowable demand factors are permitted to size all feeder loads to various panels. My argument is the demand factors given in NEC part III 220 are allowed to be applied to the all feeders (cooking appliance demand factors 220.55, lighting demand factors220.42, appliance demand factors 250.33, etc.) .
Load calculations for a large house
- Thread starter wyboy
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luckylerado
Senior Member
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- Lake of the Ozarks
For argument sake, if you applied the demand factor to each feeder (assuming 3 200 amp panels) and then pull the ovens and dryers and HVAC out of just one of those panels, how do you justify applying demand factors to the other 2 feeders?
You can only apply demand factors to the feeder for which the feeder qualifies. The loads supplied by each feeder determine which demand factors apply to that feeder. For example, you cannot apply general lighting demand factor (220.42) to a panel feeder that has no general lighting load.
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