Nec

[edawson]

A 4-wire, 120 V. multi-wire branch circuit that serves electric discharge lighting in a food store shall have the branch circuit conductor's allowable ampacity adjusted (derated) ? What section can I find the answer?

 

[Smart $]

I'm not aware of any such requirement regarding electric discharge lighting in any specific location. The only circumstance under which I believe [additional] derating may be required is when the neutral conductor is considered a current-carrying conductor (ccc) and the multi-wire branch circuit is thereby 4 ccc's instead of 3 ccc's. See 310.15(B)(4)(c). But it is further my belief, this only the case for some electronic ballasts, not your typical, non-electronic ballasts.