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25 KVA Transformer grounding #186569
05/19/09 03:23 PM
05/19/09 03:23 PM
wewire2  Offline OP
Joined: Nov 2002
Posts: 244
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.

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Re: 25 KVA Transformer grounding [Re: wewire2] #186577
05/19/09 09:14 PM
05/19/09 09:14 PM
Yoopersup  Offline
Joined: Mar 2003
Posts: 840
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
wewire2  Offline OP
Joined: Nov 2002
Posts: 244
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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