big john
Senior Member
- Location
- Portland, ME
Re: Maximum # of NM-B per drilled hole?
Alright, two things:
NEC says that derating applies to more than three current carrying conductors run together. It seems to me then, that you would be limited to one piece of Romex through holes before you had to derate.
Unless the grounded conductor isn't actually counted as a current carrying conductor? If that's the case, could someone explain why?
Also: My understanding is that derating was applied to conductors to compensate for the build-up of heat. It seems strange that pieces of Romex run in an un-insulated space, where 14.5 inches out of every 16 is free air, would be subject to the same derating rules as circuits in, say, PVC. Seems to me that heat would be much better dissipated by the Romex than anything in conduit.
-John
Alright, two things:
NEC says that derating applies to more than three current carrying conductors run together. It seems to me then, that you would be limited to one piece of Romex through holes before you had to derate.
Unless the grounded conductor isn't actually counted as a current carrying conductor? If that's the case, could someone explain why?
Also: My understanding is that derating was applied to conductors to compensate for the build-up of heat. It seems strange that pieces of Romex run in an un-insulated space, where 14.5 inches out of every 16 is free air, would be subject to the same derating rules as circuits in, say, PVC. Seems to me that heat would be much better dissipated by the Romex than anything in conduit.
-John
