North Liberty and South Bend, Indiana | Its in the NEC codes somewhere that specifically says you over size breaker. Like it or agree with it or not that is how it is done correctly. Yes you can get by and be code approved by sizing the breaker and wire much bigger than needed.
The breaker, even way oversized for conductor will trip in the event of a short circuit. The conductor will not heat up in a short circuit event, it will trip the breaker or blow the fuse. You are confusing over current with short circuit, in a dedicated motor circuit the two are separate. The motor itself should have a built in overcurrent device which will not allow the motor to draw more amps than the conductor so the conductor will not over heat and melt. The breaker or fuses will open in the event of a short circuit. The breaker or fuses are to be sized about 150-300% of the motors FLA rating from the NEC chart. The conductors are to be sized 125% of the motors amp rating from the NEC charts, not the nameplate! And the overcurrent devices, not the breaker or fuse!, are to be 115-125% of the motor nameplate amp ratings.
Or so I've been told, not a certified electrician.
Edited by Farms With CASE 10/19/2017 11:31
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How big of wire do I need?
