Ambient Temperature Rating

Temperature at which the continuous current
rating (handle rating) of a circuit is based; the
temperature of the air immediately surrounding
the circuit breaker that can affect the thermal
(overload) tripping characteristics of a thermalmagnetic
circuit breaker. Electronic trip circuit
breakers, however, are insensitive to normal (-
5o to 50o C) ambient conditions. UL standard
489 listed circuit breakers have an ambient
temperature rating of 40o C.