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

Product Line:
Circuit Breakers

Electrical Distribution Equipment

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 100A 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 100A or less is 60 deg. C unless otherwise marked.

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