Search FAQs

If the lugs on a breaker are 90 degree C rated, can I use 90 degree C wire at its rated ampacity?

Issue:
90 degree C wire at it's rated ampacity for 90 degree C rated breaker.

Product Line:
Circuit Breakers

Resolution:
No. The 2011 NEC defines the temperature rating for circuit breakers as follows:
Per NEC 110.14 (C)(1)(b), the termination temperature rating for breakers rated above 100 A or marked for conductors larger than #1 AWG is 75 deg. C. Note that higher temperature rated insulation (such as 90 deg. C) is permissible, but the wire must be sized per the 75 deg. C column of Table 310.15(B)(2)(b) in the 2011 NEC.

Per NEC 110.14 (C)(1)(a) the temperature rating for breakers rated 100 A or less is 60 deg. C unless otherwise marked.