Multi-Service Entrance Grounding

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Ray Watkins LEEDAP

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Louisville, Kentucky
Existing: Apartment complex with buildings that have existing 1200A, 120/240V, 1Phase services that are to remain. Each building has a separate utility transformer. One building has two existing 1200A, 120/240V, 1Phase services that are to remain and are fed from the same utility transformer. (each existing buliding has one Utility Transformer)

New: We are adding a new 400A, 120/208V, 3Phase service entrances to each of these buildings fed from a new utility transformer. The new services are in the same room in most buildings. Some buildings they are in adjactent rooms. The building with the two existing services will have two new 400A, 120/208V, 3Phase servies.

Question: Grounding or Bonding? 1)Do we ground the new service entrances with a new grounding system? 2)Do we ground the new service entrances with a new grounding system then bond to the existing service? 3)Do we just bond the new service ground to the existing service entrance ground? 4)Or do we....?

Separately Derived Systems on this has me confused.

P.S. We are going to comply with NEC 225.37 "Indentification".
 
IMHO and we just did one similar. We used the grounding electrode(s) just like a new service. This bonded the two separate systems.
We had to get special permission from the AHJ's because ours was the same building but different location.
 
IMHO, You would need to check the size of existing grounding electrode conductors and see if thy were adequate for the addition of the kcmils of your added service. If they are, you can tap to them.
If not you would need to run new grounding electrode conductors to the existing electrodes.
(with the #6 max for rods and #4 max for CEE, I would think you could tap to these and you might need new to water & steel).

I don't see where SDS would apply here. You seem to simply have added utility service not a SDS.
 
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