Derating of conductors

[gunny7]

Hopefully this is a quick question for you experts out there because there seems to be confusion here. Art. 310-152(a) Adjustment Factors: Example: If Bob ran 7 #12 AWG copper THWN wire in 1 inch EMT what is the ampacity of each wire? Table 310-15(b)2(a) or Appendix B Table 310-11 ? Thanks Gunny

 

[iwire]

Re: Derating of conductors

Originally posted by gunny7:
If Bob ran 7 #12 AWG copper THWN wire in 1 inch EMT what is the ampacity of each wire? Table 310-15(b)2(a) or Appendix B Table 310-11 ? Thanks Gunny

I am Bob am I running all current carrying conductors or a mix?

I would use Table 310.15(B)(2)(a)

 

[dereckbc]

Re: Derating of conductors

There is no 310.152. But the answer assuming all 7 conductors are carrying load current is 17.5 amps per 310.15(B)(2)(a).

 

[don_resqcapt19]

Re: Derating of conductors

First, per 310.15(A)(1) and B310.15(B)(1) you can only use the tables in Annex B under engineering supervision. If all seven of the conductors are current carrying, then you have a 70% adjustment factor and as Dereck said the ampacity of the conductors are 17.5 amps. However I have never seen THWN that was not also listed as THHN. If the wire is THHN the ampacity would be 21 amps.
Don