grounding 2-4000amp services to same bldg

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sevlander

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We have two new 4000 amp services going onto the same building. One at 208 volt and one at 480 volt. Each service is to get a 3/0 cu ground to the water main, building steel, etc. They enter the building about 100' apart. Can we run one ground sized for the total of both and tap it at each service with irreversible means? If so what size for the main run and what size for the taps? What article(s) are you using to interpert the answer! Thanks
 
Refer to 250.58, 250.64 and 250.66. Once your service entrance conductors total area are larger than 1100 MCM cu, the maximum size GEC required is 3/0. So your feeder cable and taps are not required to be larger than 3/0 per 250.66
 
Thanks. The reason I ask the question was we had a similar situation with a 400amp and 200amp dual service. The inspector wanted a GEC sized for the combined size from the larger service. The smaller service could be sized for 200 amp and landed on the neutral bar of the larger service. Do you agree with this connection (makes sense to me) and can it be done that way in the dual 4000amps with 3/0 thru out?
 
sevlander said:
Thanks. The reason I ask the question was we had a similar situation with a 400amp and 200amp dual service. The inspector wanted a GEC sized for the combined size from the larger service. The smaller service could be sized for 200 amp and landed on the neutral bar of the larger service. Do you agree with this connection (makes sense to me) and can it be done that way in the dual 4000amps with 3/0 thru out?
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I disagree that you can land the GEC tap from the larger service disconnect neutral terminal bar to the small service disconnect neutral terminal bar refer to 250.64 C and D however some jurisdictions may permit this method
 
QES said:
can you use 250.66(a) on this?
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OP is taking about metal water pipe or building steel not those eletrodes list in 250.66(a) but if those list in 250.66 (a) is all that is present at the structure yes you could
 
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