What is the temperature rating of the lugs on circuit breakers? (75C? 90C?)
UL Listed Circuit Breakers
The wire temperature rating allowed for use in circuit breakers lugs is 75C. While it is acceptable to use 90C wire, that 90C wire must be sized as if it is 75C wire. This is according to the UL standard for circuit breakers, which is summarized as follows:
(1) Breakers rated 125A or less must be marked for use with 60C, 60/75C, or 75C only wire.
(2) For breakers rated more than 125A, the proper wire temperature rating is 75C, and the marking is optional.
(3) Wire with a higher temperature rating can be used (e.g. 90C), but the ampacity of the wire must be based on the wire temperature marked on the breaker.
Therefore, as marked on the breaker, the wire must be sized as if it is 75C wire.