Say I have an outdoor pad Mount utility transformer and a service disconnect in close proximity to each other, let's say 8 to 10 ft. Let's say the utilities spec is typical where the secondary center tap is bonded to the transformer case and connected to a grounding electrode. If the distribution system is a MGN we will also have the primary neutral connected to the xformer can, but whether it's an MGN or a Delta shouldn't effect the answer to this question. The question is do I use the same grounding electrodes for both the utility grounding and for the service disconnect grounding, or keep them separate? Would the answer be the same if the transformer was a customer owned SDS?
Where I’m at, their electrode is inside the pad next to their ducts, so we’d never be able to get access to it, and the GEC would have to be inspectable at the service entrance? If their rod is not inside the pad footprint, then I think the only thing holding you back is the utility rules.
If it was a customer owned transformer, then you’re for sure in the clear — as long as it’s inspectable.
I have, and regularly do, share the same rod with clustered equipment — even though I usually get a weird look, I’m not into driving rods in proximity because they want to see it that way or the plan shows it that way because distance wasn’t factored in.
Likewise, I absolutely refuse to sink a rod on ground mount PV projects with driven piles, helical piers, or screw piles. 100 bonded 7ft embedment C channels… and a ground rod. No way.
