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Monday, September 16, 2019

Question:

Can a 120/240v panel be fed from a 120/208v feeder?

Domenic Ladevaia
A

Answer:

Hey Domenic thanks for your question. Equipment must have a voltage rating at least that of the circuit supplying it as stated in 110.4 so the voltage rating part is OK. You don't mention whether the 208/120-volt feeder is three phase and if the panelboard is single phase it can't be supplied by a three-phase circuit. Some equipment, such as utilization equipment, can have minimum voltage levels that are necessary. The loads would also need to be suitable for being supplied by the 208/120-volt source and if the panelboard instructions state it can only be supplied by a 120/240-volt circuit then it is not acceptable as stated in 110.3(B). Marking the panelboard with the nominal supply voltage seems like a good idea also.

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