220.61(c) vs 250.24(C)(1)

[m sleem]

I see there is a conflict between these two sections for neutral sizing, am i missing something here?

 

[jaggedben]

I don't see a conflict.

 

[david luchini]

I don't see a conflict, either.

 

[Dennis Alwon]

I see there is a conflict between these two sections for neutral sizing, am i missing something here?

Why not try and explain what the conflict is that you see.

 

[Dennis Alwon]

Here is what 220.61(C) states. It is talking about circuits where there are 2 hots and a neutral on a 3 phase system (wye) and a circuit that has non linear loads...

(C) Prohibited Reductions. There shall be no reduction of
the neutral or grounded conductor capacity applied to the
amount in 220.61(C)(1), or portion of the amount in (C)(2),
from that determined by the basic calculation:
(1) Any portion of a 3-wire circuit consisting of 2 ungrounded
conductors and the neutral conductor of a 4-wire,
3-phase, wye-connected system
(2) That portion consisting of nonlinear loads supplied from
a 4-wire, wye-connected, 3-phase system

Section 250.24(C)(1) is talking about the smallest size of a grounded conductor. Obviously if the neutral (grounded conductor meets the criteria in 220.61(C) then you cannot reduce the neutral

(1) Sizing for a Single Raceway or Cable. The grounded
conductor shall not be smaller than specified in Table
250.102(C)(1).

 

[m sleem]

Why not try and explain what the conflict is that you see.

That's may be unintentional mistake

 

[m sleem]

Here is what 220.61(C) states. It is talking about circuits where there are 2 hots and a neutral on a 3 phase system (wye) and a circuit that has non linear loads...




Section 250.24(C)(1) is talking about the smallest size of a grounded conductor. Obviously if the neutral (grounded conductor meets the criteria in 220.61(C) then you cannot reduce the neutral

So, full neutral is applicable for non-linear loads only?

 

[jaggedben]

No, that's not what 220.61(C) says. It state specific situations where you cannot reduce the neutral size. It does not say that you can reduce the neutral size in all other situations. If you do not have any balanced load then you cannot reduce the size. Read the rest of 220.61 that comes before it.

250.24(C) just puts a hard floor on how small the neutral can be regardless of any unbalanced load calculation. Whichever minimum size is larger, you have to go with that.

 

[m sleem]

Thanks for all..