Is it necessary to derate cables when installed within equipment, like switchboards or equipment cabinets? It seems silly to think that if I pop up and run, say, 3 cables each through 4 conduit sections consisting of two elbows joined end-to-end, I can use 100%, but if I run the 12 cables directly from one cabinet to the next (>24" total length), and strictly adhere to 310.15(B)(2)(a) I have to derate 50%, or even more considering the other cables in this equipment. I know I could pretend they're spaced, or separate them at points to pretend they're only bundled for 24" at a pop, but I'm pragmatic enough to know that's not meeting the intent of the code, and I'm far more interested in safety than I am in technicalities.
Are there special rules covering cable troughs and equipment that allow for lesser derating for short cables in equipment?
[This message has been edited by SteveFehr (edited 03-06-2007).]
