2 adjacent things with earthing requirements

[electrofelon]

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?

 

[cadpoint]

I thought an Isolated ground was a myth?

I never not brought it all together (and that's a double negative)

Grounding Electrodes

iaeimagazine.org

 

[jaggedben]

I think I always think you can use the same electrodes if you want. Earth is earth. Unless someone involved (utility?) has some dumb rule to the contrary.

 

[LarryFine]

Generally, electrode systems can be shared, but this will create a parallel neutral-current pathway.

Transformers and disconnects aren't usually so close, and earth is not considered a current path.

 

[BackCountry]

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.

 

[electrofelon]

FWIW, let's say in the case of utility transformer I am installing the pad and ground ring with two rods for their specs so there is no issue with access, different timing etc.

On one hand, I don't like the parallel path created through the gec's. On the other hand, I like having everything bonded together, but of course the neutral conductor is bonding them together,. So I guess the gecs was shared electrodes just make it "more bonded together"

 

[wwhitney]

On one hand, I don't like the parallel path created through the gec's.

If you are able to route the GEC alongside the neutral conductor, then is there any real downside to the parallel path?

Cheers, Wayne

 

[electrofelon]

If you are able to route the GEC alongside the neutral conductor, then is there any real downside to the parallel path?

Cheers, Wayne

Yeah I suppose not, just one of those things I think we are conditioned to be opposed to but can't come up with a good reason.

 

[Tulsa Electrician]

How about a couple one lines to aid in responses.
I do have a few thoughts.
One is bonding versus grounding.
Service versus SDS

 

[ActionDave]

I would use the same electrodes. l can't see any real world problem with the parallel path issue and having everything bonded together is better in case of a surge or lightning strike.