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how to size circuit breakers and fuses for FLA rated loads

Question asked by ventruella@gmail.com on Jan 21, 2018
Latest reply on Jan 21, 2018 by ventruella@gmail.com

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?

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