Service Neutral

[thinfool]

I have a 1000 amp service to build next week. 3-4" conduits from a pad mounted xfmr to the main panel. (208/120Y) 85% of the load is phase to phase (resistance heating).

I will use 3-500kcm in each conduit...my question...can I use..say...a 3/0 for the neutral in each conduit?

Code ref. ?

 

[roger]

Re: Service Neutral

Thinfool, your question is more involved than "can I use a certain size conductor for the neutral", in most circumstances you would need to do the complete feeder or service calculation per article 220 which will lead you up to 220.61 for the neutral conductor.

Since you know the neutral connected loads are light, you can get buy with out the in depth calculations. Use what you know the maximum unbalanced grounded conductor load would be, but it's not a rule of thumb so to speak.

Roger

[ August 19, 2005, 11:01 PM: Message edited by: roger ]

 

[mkbuck]

Re: Service Neutral

250.24(B)(1)&(2) In addition to meeting the requirements of 220.61, the grounded conductor brought to the service equipment cannot be less than the grounding electrode conductor specified in 250.66.

When the equivalent area of the (largest)ungrounded service conductor(s) exceeds 1100 kcmil copper or 1750 kcmil aluminum, the grounded conductor cannot be less than 12 1/2% of the equivalent area of the ungrounded service conductor(s).

The installation as described would allow for a maximum unbalance load of 600 amperes and meet the requirements of 250.24(B).

MB

[ August 20, 2005, 12:07 AM: Message edited by: mkbuck ]