Quick minimum service/feeder neutral sizing

[conmgt]

For a quick way to calculate a minimum neutral size, could you base that calculation on the ungrounded conductors or breaker?

e.g. 3ph 4 wire service/feeder 600A breaker. The first 200A at 100% and then the balance of 400A at 70% = 200 + (.70 * 400) = 200 + 280 = 480A

e.g. 3ph 4 wire service/feeder (2) 500MCM AL XHHW rated 620A. The first 200A at 100% and then the balance of 420A at 70% = 200 + (.70 * 420) = 200 + 294 = 494A = (2) 350MCM

This idea just popped into my head as I read Article 220 and I'm blurting it out.

 

[Dennis Alwon]

When you speak of minimum then it will be based on the calculated load not the wire size or breaker sizes.

The actual minimum service neutral cannot be smaller than T. 250.66. The smallest neutral feeder cannot be smaller than the equipment grounding conductor. Of course if the loads demand a higher amp. than these conductors then you must increase them accordingly

Be careful of art. 220.61(B) as the neutral there is based on (1) and (2) in the art.-- not as simply as you suggest