AnsweredAssumed Answered

how to size circuit breakers and fuses for FLA rated loads

Question asked by on Jan 21, 2018
Latest reply on Dec 2, 2018 by tranzz4md

If one applies the NEC to new equipment installations, how does one do it regarding equipment rated with FLA?  If a circuit breaker rating based on 1.25 x FLA exactly matches a breaker size that is real, then 0.8 (80% rated breakers) will exactly match the FLA of the load.  That seems to be a problem to me.  If the load were ever to reach FLA the breaker will eventually trip.  The same is true for 100% rated fuses.  If I size a fuse for the FLA, then it will blow if the FLA is ever reached.  Any insights on how one deals with this when sizing breakers and fuses?