# 220.61 Derating Service Neutral



## dronai (Apr 11, 2011)

cheezhd2008 said:


> I'm having trouble interpeting 220.61. Do both 1 and 2 have to apply?, or is it either or. my question is can you derate the grounded conductor on a 100A residential service? on a 200a?
> 
> Thanks for the help.


 
Yes you can for residential services


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## erics37 (May 7, 2009)

cheezhd2008 said:


> I'm having trouble interpeting 220.61. Do both 1 and 2 have to apply?, or is it either or. my question is can you derate the grounded conductor on a 100A residential service? on a 200a?
> 
> Thanks for the help.


By "derate" I assume you mean "reduce the size of" and yes you can.

Your grounded conductor is sized to carry the calculated neutral load, which is defined in 220.61(A). You are permitted to reduce your calculated neutral load if either, or both, of the conditions in 220.61(A) or (B) apply. So if you have ovens and dryers and stuff, the portion of the service load supplying them can be reduced by 30% for the neutral load.

Standard typical residential 200 amp service in aluminum wire would be 4/0 for the hots and 2/0 for the neutral.


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## cheezhd2008 (Jan 3, 2009)

Thanks for the input


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## Shockdoc (Mar 4, 2010)

I've derated 200 amp commercial three phase neutrals to 1/0. it all evens out.


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