question on NEC tables 310.15 (B)(1) and 310.15(c)(1)

[Matt the electrician]

Hello,
my question is simple do the NEC tables 310.15 (b)(1) and 310.15(c)(1) apply on to 90 degree C conductors only or to the 60, 75, and 90 degree C conductors of Table 310.16?
I'm asking this because there seems to be a lot of debate about the code language of NEC 310.15 (A)
thanks,
Matt

 

[wwhitney]

The conductor insulation temperature has no bearing on the application of Table 310.15(C)(1) "Adjustment factors for more than three current-carrying conductors."

For Table 310.15(B)(1) "Ambient temperature correction factors based on 30C", you pick the column corresponding to the insulation temperature of your conductor, assuming your base ampacity comes from one of the Tables that indicates a 30C ambient temperature. Or you can use Equation 310.15(B) directly.

Cheers, Wayne

 

[charlie b]

Example: If you are using a #6 conductor of a type that has a temperature rating of 75C, such as THHW, and you put 4 such conductors in the same conduit, your ampacity is 65 (per table 310.16) times 80% (per table 310.15(C)(1)), for a net of 52 amps. Does that answer your question?

 

[Matt the electrician]

Both answers have been helpful, Thank you