Transformer Secondary Conductor Derating

[Canton]

I have argued about this before. Do we have to derate the secondary conductors of a 4 wire 208/120Y transformer to 80%, based on having 4 current carring conductors in a raceway? Is the neutral conductor in this case current carring? (no harmonic loads also)

I am siding on no becuase of 310.15(B)4......a neutral conductor that carries only the unbalanced current from the other conductors "of the same circuit" shall not be required to be counted when applying the provisions of 310.15(B)(2)(a)....

Thanks

 

[iwire]

I agree with you.

 

[Smart $]

No siding to it. The neutral is not counted as a CCC unless the majority load is non-linear.

Welcome!

 

[augie47]

Do make note, however, from 240.21(C):

"The provisions of 240.4(B) shall not be permitted for transformer secondary conductors."

It is not uncommon to find 500 kcmil transformer secondary conductors terminated on a 400 amp C/B.