bphgravity
Senior Member
- Location
- Florida
Is there such a rule that says "double derating" is not required. The argument is that if you are required to derate the ampacity of a conductor per 310.15(B)(2)(a) and 310.16 correction factors, then you don't have to derate for temperature limitations on terminals per 110.14(C). I believe that you must do all that apply. Once you have made all corrections for ambient temperature and amount of current carrying conductors, you still can only select the wire size based on the column of the lowest terminal rating on the circuit, regardless of the insulation rating of the used conductor.