if we have a motor with 300amp as normal curent. what is the frame size of its circuit breaker acording to NEC? Our electrical engineer stated that the NEC saying the frame current of the breaker should be 300 times 2.5 which mean the size not less than 700amp. is this correct. thanks
sizing a circuit breaker for motor
- Thread starter sahafi
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- Illinois
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- retired electrician
Table 430.52 permits the branch circuit breaker to have a rating of up to 250% of the full load current for the motor. It does not prohibit the use of a smaller rated device, but if it is much smaller the breaker may trip on the starting current.
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