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25 KVA Transformer grounding #186569
05/19/09 03:23 PM
05/19/09 03:23 PM
W
wewire2  Offline OP
Member
Joined: Nov 2002
Posts: 244
California
Would it be OK to run the grounding electrode conductor for a 25 KVA 3 phase 480-208Y/120V transformer to the existing service ground in the adjacent switchgear? The only accessible building steel is bolted together lattice trusses(not a reliable ground)and the water entrance piping is not in the vicinity? Driving a ground rod would be extremely risky due to existing unknown substructures.

2017 / 2014 NEC & Related Books and Study Guides
Re: 25 KVA Transformer grounding [Re: wewire2] #186577
05/19/09 09:14 PM
05/19/09 09:14 PM
Y
Yoopersup  Offline
Member
Joined: Mar 2003
Posts: 849
Michigan
I'd say read 250.30 A(7)
Exception # 2.
2005 N.E.C.

Re: 25 KVA Transformer grounding [Re: Yoopersup] #186584
05/20/09 02:57 AM
05/20/09 02:57 AM
W
wewire2  Offline OP
Member
Joined: Nov 2002
Posts: 244
California
Good advice,thank you. I skipped right over that exception in my quest for the answer. The transformer is fed from a subpanel that is fed from the switchgear. I guess the next step is to verify whether the subpanel is suitable for use as service equipment.
Now I'm wondering what criteria the manufacturer must abide by in having their product listed as suitable for use as service equipment.


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