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Can I terminate 90 deg. C rated conductors on a circuit breaker if the lugs are rated for 75 degrees C?

Issue:
Can I terminate 90 deg. C rated conductors on a circuit breaker if the lugs are rated for 75 degrees C?

Product Line:
Circuit Breakers 

Environment:
Installation 

Cause:
Wire Pulled

Resolution:
It is alright to use 90 deg. C rated conductors, BUT they MUST be sized by the 75 deg. C column of NEC Table 310.15(B)(2)(b), when terminated on a breaker with 75 deg. C terminations (Lugs).  Circuit breaker terminations are 75 deg. C maximum and in some cases 60 deg. C.
When applying derating factors, you can begin with 90 deg. C rated ampacity, but after applying derating factors the allowable ampacity will be the lower of the calculated ampacity, or the 75 deg. C ampacity, for a 75 deg. C terminated breaker.  The conductor allowable ampacity must be protected by the required overcurrent device.


 
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