NEC 2020 Table 310.15(B)(1)

[Zyb]

For derating conductors base on Table 310.15(B)(1). if I use 90 degree rated conductor but will terminate on 75 degree breaker. do I use the 90degree column or the 75 degree column?

 

[david luchini]

For derating conductors base on Table 310.15(B)(1). if I use 90 degree rated conductor but will terminate on 75 degree breaker. do I use the 90degree column or the 75 degree column?

90 degree column

 

[Dennis Alwon]

For de-rating you use the 90C but the circuit ampacity after de-rating can not be greater than the 75C column.