paulohpm Posted June 25, 2019 Report Posted June 25, 2019 Hello,I am sizing a feeder circuit for a panel according to UL 508A and came into a question:My input current is of 76.5 A (considering all the loads), thus, it is fine for me to use a cable of 4 AWG (max. 85A @ 75 c).For the circuit breaker I did 76.5 A x 1.25 = 96 A and then I selected a breaker of 100A.My question is: Is it ok for me to keep this configuration according to UL 508A? 100A breaker + 4 AWG load side cableOr do I need to level up the cables?Thank you very much in advance! Quote
pcmccartney1 Posted July 2, 2019 Report Posted July 2, 2019 The purpose of the breaker is to protect the wire and it's insulation from melting or starting a fire. If the breaker is oversized for the wire, then you are essentially protecting nothing. Quote
NevergoldMel Posted July 8, 2019 Report Posted July 8, 2019 Spec the wire at 125% of maximum possible load. Spec the breaker at 90% of the wires load rating. In most locales this should exceed the code requirements. Quote
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