Ground to seperate building

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GaTech04

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We are renovating a building whose panel is fed from another building on the premises. The panel is 150A MB, and the feeder is existing. I just found out today the feeder is #3/0 AL with a #6 AL ground and the panel is also grounded to a ground rod with #6 CU and to building steel with a #4 CU.

According to 250.122 it looks like the panel would need a #4 AL ground. I think it would be near impossible to repull that - so I was wondering if we could just abandon the ground (we are on '05 code) and just use an improved grounding system in the building in which we are working.

Thank you.
 
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GaTech04

Member
Assuming I havent confused anything, it looks like the main constraints are in 250.32 (B) (2).

1) Grounding conductor not run (well it is, but we can delete it)
2) The buildings arent bonded (check - buildings dont touch and the feeder is in PVC)
3) No GFI on the supply side (check)
+ Neutral is sized properly (check)

If all the above is true, we should be ok as long as we long as we ground per 250.50, correct?

Thanks again for the help.
 
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GaTech04

Member
I would have to verify, but I believe all telecom/CCTV/Sec is underground PVC and there are no overhead connections.

If there was something that bonded the two structures that couldnt be removed we would be forced to repull the feeder with a proper sized ground, correct?
 
iwire

iwire

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GaTech04 said:
I would have to verify, but I believe all telecom/CCTV/Sec is underground PVC and there are no overhead connections.

If there was something that bonded the two structures that couldnt be removed we would be forced to repull the feeder with a proper sized ground, correct?
Click to expand...


Yes, and at the least the CCTV is required to be bonded at each building so it seems you will be re-pulling.
 
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GaTech04

Member
Thanks for the help guys - very timely and clear responses as usual!

Well it appears there is no CCTV, just voice and data. I'll have to make a trip out to the site to verify everything it seems.

EDIT - I suppose the only other option would be to reduce the panel size to 100A. Im sure they wont want to do that, but it is an option! Current Demand for the building is 69.4 kVa @ 480V = 83.6A.
 
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wwhitney

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GaTech04 said:
EDIT - I suppose the only other option would be to reduce the panel size to 100A. Im sure they wont want to do that, but it is an option! Current Demand for the building is 69.4 kVa @ 480V = 83.6A.
Click to expand...
I think 250.122(B) (2008 NEC) would put the kabosh on that option.

Cheers, Wayne
 
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