What are the NEC rules for sizing conductors terminated on a circuit breaker?
Issue:
How to determine what size wire should be used on a circuit breaker
Product Line:
Molded Case Circuit Breakers
Resolution:
Per NEC 110.14(C)(1):
Conductors must be sized based on the 60 deg. C or 75 deg. C column of Table 310.15(B)(16) that corresponds to the terminal rating of the circuit breaker.
(a) Equipment rated 100 A or less must be sized using the 60°C column of Table 310.15(B)(16) UNLESS marked for use with 75 deg. wire, in which case the 75 deg. column is used.
(b) Equipment rated over 100 A must be sized using the 75°C column of Table 310.15(B)(16).
Wire with higher insulation temperatures can be used provided it is sized appropriately per NEC rules summarized above.
Schneider Electric typically marks circuit breakers with terminal (conductor) temperature ratings only on frame sizes with ampacities of 100 A or less.
Circuit breakers rated over 100 A are required to be terminated with conductors rated at least 75 deg. C and so are not typically marked with the temperature rating.
How to determine what size wire should be used on a circuit breaker
Product Line:
Molded Case Circuit Breakers
Resolution:
Per NEC 110.14(C)(1):
Conductors must be sized based on the 60 deg. C or 75 deg. C column of Table 310.15(B)(16) that corresponds to the terminal rating of the circuit breaker.
(a) Equipment rated 100 A or less must be sized using the 60°C column of Table 310.15(B)(16) UNLESS marked for use with 75 deg. wire, in which case the 75 deg. column is used.
(b) Equipment rated over 100 A must be sized using the 75°C column of Table 310.15(B)(16).
Wire with higher insulation temperatures can be used provided it is sized appropriately per NEC rules summarized above.
Schneider Electric typically marks circuit breakers with terminal (conductor) temperature ratings only on frame sizes with ampacities of 100 A or less.
Circuit breakers rated over 100 A are required to be terminated with conductors rated at least 75 deg. C and so are not typically marked with the temperature rating.
Released for: Schneider Electric Canada
