310.15(b)(4)(a)

[unicorn]

Could some one please give me an exp. of when or how a neutral doesn't count in the derating process. Just a lowly 3rd year thats confused!
Thanks in advance
Unicorn

 

[ron]

Re: 310.15(b)(4)(a)

Consider the feeder to a 3 phase 4 wire circuit breaker panelboard. If the load is balanced and zero or minimal harmonics, then the neutral current (unbalance between phase conductors) could be considered zero.

 

[unicorn]

Re: 310.15(b)(4)(a)

I am asking about the derate in a pipe with branch circuts in it. Like if you use 1 neutral for one circut does that neutral count as a current carrying conductor, as per the article in my title
thnx unicorn

 

[earlydean]

Re: 310.15(b)(4)(a)

That was exactly what ron was giving you. When a current flows in a multiwire circuit, any current in the "hot" legs cancel each other out. This is best shown vectorally on the chalkboard.

 

[caj1962]

Re: 310.15(b)(4)(a)

Unicorn
What the others are telling you is one hot one neutral yes it counts towards derating in the conduit. 3 hots(all of differant phases) sharing a nuetral then it would not count because the neutral would have 0 or very little current on it.Hope this helps