Clarification on 430.52 please

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Telaid

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In 430.52 (A), the explanation talks about the short circuit / ground fault fuse OR circuit breaker being able to carry the starting current of the motor and may be sized 150-300% of full load.

Where does this 150-300% come from? Looking at table 430.52 it appears its form the non time delay fuse column but the explanation says fuse OR circuit breaker. Can anyone help me out on this?

Then the explanation further states conductors with an ampacity of 125% (not 150-300) are reasonably protected by devices set to operate at same as conductor ampacity.

Im just confused and would like some help :( Is the branch conductor sized at 125 % of FLC? Then what about the best setting of the breaker? Table 430.52 gives the max but if you dont know starting current, what is best for sizing?

This sounds confusing im sure but its confusing to me as well.

any help appreciated.

Thanks,
Ron
 
The 150-300% should be the difference in the type of OCP you are using 430.52.

125% conductor size see 430.22.

The starting current is allowed for in the oversizing of the OCP
 
430.52 Rating or Setting for Individual Motor Circuit.
(A) General. The motor branch-circuit short-circuit and ground-fault protective device shall comply with 430.52(B) and either 430.52(C) or 430.52(D), as applicable.

This is how it reads in my book!? No % values at all.
 
I agree, they would be protected on a ground fault or a phase to phase fault, but would be they protected for example on an overload condition?

Hank
 
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