peter d
Senior Member
- Location
- New England
We derate the conduit to reduce problems from the effect of heating, all conduits are enclosing the conductors, and in metal conduits, we have the additional effect of not just current loading, but also the added effect of induced induction loads, and these loads can, if not derated, reach a temp hot enough to cook an egg.
It would be nice for the OP the read up and learn as much as he can about derating, it is not a cut and dried, read the table. and just do it issue.
I understand the principle of induction. I also don't see that the NEC addresses it with regard to derating.
The inductive heating you mention is a result of isolated phase conductors being run in a metal raceway, or running the grounded conductors in a separate raceway away from the ungrounded conductors, both of which are code violations and have nothing to do with derating.