Any Code Involving Downsizing Neutral And Ground For A Subpanel? - Electrical - DIY Chatroom Home Improvement Forum


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Old 05-17-2012, 08:28 PM   #1
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Any code involving downsizing Neutral and Ground for a subpanel?


I am planning on a couple of subpannels that will be required to supply fairly robust 240v load, but minimal 120v loads. I was thinking of running 00/2 - 2/2 (maybe a size smaller, I haven't measured the run yet). would that pass code?

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Old 05-17-2012, 09:34 PM   #2
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Any code involving downsizing Neutral and Ground for a subpanel?


For most household applications the neutral has to be the same size as the hot conductors, but the ground wire can be somewhat smaller. The National Electric Code has a table listing the ground wire sizes.

But with a predominantly 240 volt load you might use the 240 volt calculatoin instead of the 120 volt calculation for percentage voltage drop when selecting the wire size to begin with, if the distance is considerable. Voltage drop takes into account the round trip distance. Wiith the predominantly 240 volt load the number of amperes and therefore the voltage drop in the neutral will be somewhat less than the 120 volt calculation shows, leading to an actual smaller overall percentage voltage drop fort he 120 volt loads. (The percentage voltage drop will always be greater or equal for the 120 volt loads compared with the 240 volt loads.)

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