Second electrical grounding?

[Wannaretire]

City inspector said we need a second electrical grounding.
Tesla came out on Fri, and were going to drill/dig 8 feet for a second grounding. I asked how they would know if its safe, they said 'OK. We can delay and call 811 to check what's underground.

1. Anyone with experience dealing with this?
2. Is my city just doing overkill by needing a second electrical grounding?

Appreciate any pointers.

Thanks

 

[BGbreeder]

City inspector said we need a second electrical grounding.
Tesla came out on Fri, and were going to drill/dig 8 feet for a second grounding. I asked how they would know if its safe, they said 'OK. We can delay and call 811 to check what's underground.

1. Anyone with experience dealing with this?
2. Is my city just doing overkill by needing a second electrical grounding?

Appreciate any pointers.

Thanks

We had to have two ground rods as well, on both roof tops. Different county. I'm surprised Tesla didn't catch it, and I'm surprised that they wouldn't have called 811 automatically...

I will let others who know way more than I do (e.g. @Vines or @wwhitney?) comment on whether having two grounds is overkill. I think of it as cheap insurance...

All the best,

BG

 

[BrettS]

Given that the grounding rod will be going quite close to the foundation of your house I feel like it’s reasonably safe to blindly insert it. Other than things that are directly servicing your house (which should be easy to identify and avoid) there shouldn’t be anything buried that close to your house.

Of course, just because there shouldn’t be anything there doesn’t necessarily mean there isn’t, so 811 is probably the safest option, but I wouldn’t be too concerned about letting them do it blindly.

 

[israndy]

I agree, and I watched a ton of videos with regulators that were uncomfortable with the final decision to ask for two grounding points. They argue that it's potentially LESS safe than just one. I was fortunate that I wasn't told to add a second one when the inspector came to sign off on my solar system. I believe it's a very confusing rule and potentially you may get different requirements depending on who your inspector is. Maybe Tesla has previously had different inspectors in your area.

The inspectors are there to help keep you safe and you have to do what they say, but not everything they deal with is black and white.

 

[wwhitney]

The NEC is very clear on the grounding electrodes requirements, whether or not inspectors are enforcing the requirements consistently:

A metal water pipe if present gets used as a grounding electrode, but does not count towards required electrodes. And a single grounding electrode that is a rod, pipe or plate is not sufficient on its own, a second electrode is required (again, not a water pipe) So for most residences you need two ground rods. If you have a foundation from this century, it should be a concrete encased electrode, in which case you use it, and you don't need any ground rods.

As to safety, I'm not aware of a mechanism by which two properly installed ground rods near each other (but at least 6' apart as required) would be less safe than a single ground rod.

Cheers, Wayne

 

[TexacoStar5]

The additional grounding rod is a requirement of NEC/NFPA 690.47 which requires two 8' grounding rods located a minimum of 6' apart