Motor Ground wire size

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brother

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Ok, I know the breaker is for 'Short circuit/GroundFault' protection and overloads (fuses in this case) is for the overcurrent/overload protection.

There was a this wire #6 ran that was off a 70 amp breaker, but the ground wire was #10. its my understanding it has to be at least a number #8, even though the breaker is for short circuit/protection. This is for a motor.

Am I right in this?? table 250.122??
 
I guess I should add. If the overcurrent device for the motor consist of a short circuit protector (Or instantaneous trip circuit breaker), then you can size the EGC based on motor overload protect. device, yet it cannot be less than T. 250.122.
 
resistance said:
I guess I should add. If the overcurrent device for the motor consist of a short circuit protector (Or instantaneous trip circuit breaker), then you can size the EGC based on motor overload protect. device, yet it cannot be less than T. 250.122.
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That was true in the 2005 code but has been changed for the 2008 code.
250.122(D)(2) Instantaneous-Trip Circuit Breaker and Motor Short-Circuit Protector. Where the overcurrent device is an instantaneous-trip circuit breaker or a motor short-circuit protector, the equipment grounding conductor shall be sized not smaller than that given by 250.122(A) using the maximum permitted rating of a dual element time-delay fuse selected for branch-circuit short-circuit and ground-fault protection in accordance with 430.52(C)(1), Exception No. 1.
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don_resqcapt19 said:
That was true in the 2005 code but has been changed for the 2008 code.
Click to expand...

I see now in that section of the 2008. So Im wright in saying they need to size it to 70 amp breaker, which would be a #8 instead of #6, because the ungrounded conductors are #6. ;) I wonder what made them change?? I does make sense since there could be a fault on the line side of the overloads.
 
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