Conductor derating

[Isaiah]

If I am using 90 degree C #12 AWG insulation can I use the 30A in Table 310.16 for derating?


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[ActionDave]

You are allowed to use the 90 degree column for derating but your final ampacity can't go more than the 75 degree column because equipment is almost always rated 75 degree.

 

[infinity]

I agree with Dave, I would add the one other scenario could be if the conductor was used in a wet location where THHN/THWN is only good for 75° C when wet. If it's THHN/THWN-2 your good either wet or dry.

 

[Dennis Alwon]

Also nm cable would be at the 60C column not 75C
You need to take note of the asterisks after 10, 12, and 14 gauge and see the bottom of the table-- it directs you to 240.4(D)

 

[Isaiah]

Thanks Gentlemen