600 amp 120/208 service

[codeunderstanding]

I am laying out the service lateral for a 600 amp 3 phase service for a 6 plex condominium complex. Heres how I figured.

600/3= 200amps 3 conductors per phase plus neutral
In 75 degree colume use 250 kcmil AL. use wire
Use three three inch conduits coming out of ground. Wires are direct buried

My question is can I get away with reducing the neutral with out any harm.
There is very little non linear loads, but there is a 20 hp elevator going in and I dont know if that takes alot of neutral current?

 

[bkludecke]

Do a load calculation on the feeder to determine the maximum load (imbalance) which can be carried on the neutral and size the conductor accordingly. A quick way to do this is to take your max load on the feeder and deduct all 240volt (phase to phase) loads.

 

[suemarkp]

See also 220.61(B)(2) since you have over a 200A service. This lets you use a value of 70% for the neutral current over 200A. So its ampacity can be 480A without doing any work. Do a load calculation to see what the neutral load really is, and then you can apply the 70% factor to the portion over 200A.

 

[don_resqcapt19]

But if you do reduce the neutral size it cannot be smaller than what is required by 250.24(C) even if the load calculations would permit it to be smaller.
Don

 

[LarryFine]

There is very little non linear loads, but there is a 20 hp elevator going in and I dont know if that takes alot of neutral current?

A 3-phase motor should have no neutral load, but its controlling circuit probably has a couple of amps' worth.