grounding & bonding separatly derived system

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karen

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I am installing a three phase transformer with a 480 primary and 208 secondary. The 480 feed is a sub panel. Can I connect the neutral for the 208 XO buss to the neutral in the 480 sub panel or must I run a new EGC from the XO buss to the system grounding electrode? The 480V panel is also used for flourescent lighting and so will be carrings 277v return current.
 
Re: grounding & bonding separatly derived system

Originally posted by karen:
Can I connect the neutral for the 208 XO buss to the neutral in the 480 sub panel or must I run a new EGC from the XO buss to the system grounding electrode?
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No. You must connect the Xo of the transformer, or neutral bus in the first disconnect device to the nearest GE. The neutral from the 480 has nothing to do with the step-down transformer.

[ November 27, 2003, 03:11 PM: Message edited by: dereckbc ]
 
Re: grounding & bonding separatly derived system

Thanks, I did not think it was right to attach the neutral from the 480 supply to the XO buss in the step down transformer. Seperatly derived system...seperatly derived neutral.
 
Re: grounding & bonding separatly derived system

Draw this system on paper. You will notice all star points are connected. Ed has a good drawing of this procedure.
 
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