Im adding a subpanel that will feed 3 arc welders. A little confused on 630.12b...it says I can have ocp at 200% of the conductor ampacity. Total for 3 welders is 79 amps...so im thinking #4 copper on a 150 amp breaker...It doesnt sound right...it would seem that if I want to use a 150 amp breaker for a sub-panel , I would have to use 1/0 copper or am I good using #4??
I feel like my numbers are right...just not sure if that 200% would apply to a panelboard...Kinda seems wrong...Ive used the 200% for a feeder ocp going to a "6 pack" of welders...but that came with a factory installed trough with ocp for each welder built in...
My understanding is that even with a 200% oversized breaker a short circuit or ground fault will still trip the breaker. And the duty cycle of the welders will prevent any long term overload of the conductors.
Is there any provision that would require me to mark the panel or not allow a non welder load in that sub panel ?
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