Message Board Thread - "Electric Equipment Max Temp (breaker.....)"

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Electric Equipment Max Temp (breaker.....) Mlopes 9/24/2010
Hi friend´s
For sometime i question my self but never found a real answer.
What is the working temperature in a breaker that work´s 24-7 and the and THD+(V) => 15% with a nominal load of 70% of the breaker? This case apply also to the termic protection of motores. i have found Breakers that goo bad @ 55 C and others that never trip even @ 70 C ?
Normally if the electric board is well dimension the inside Temp is 7 to 10 degrees higher then ambient temp but in cases were the breakers or other equipment emit lot´s of heat what is the max temp to consider as Max working condition? thank´s
Re:Electric Equipment Max Temp (breaker.....) IRJay 9/27/2010
A breaker has no stated temperature limit other than the environment. The terminations are the rated part. So if a termination is rated at 60C then the rating is such for the wire and the termination and should not exceed this value. UL489 and NEC. The 40C shown on the breaker is the max environment it is allowed in before derating. If the breaker is installed correctly within these limits it should be able to disipate its heat correctly. The imperfections such as poor contacts and terminations will therefore indicate this "extra" heating that patterns out a problem.

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