Using an electrical system grounding ring electrode in lieu of (instead of) dedicated grounding electrodes.

[corvalan]

I still do not have a clear understanding of the following hypothetical situation. One of the existing electrical system grounding electrodes is a ground ring. This ground ring satisfies all the NEC requirements. We decided to install a brand new LPS. This LPS has five down conductors. I realize that the electrical system ground ring also satisfies all the rules of the NFPA 780 for a ground ring. I consider, then, in lieu of installing dedicated LPS grounding electrodes, to use the existing electrical system ground ring. Then I read that the NFPA 780 says, "Electrical system grounding electrodes shall not be used in lieu of lightning protection system grounding". This seems to be a problem because instead of installing dedicated LPS grounding electrodes, I am using an existing electrical system grounding electrode in direct violation of NFPA 780. Any thoughts?

 

[roger]

We ran into this once so the designer showed two of the rods as part of the GES and the rest as LPS. NFPA 780 and 250.106 require the two systems be connected so all was well.

 

[winnie]

If the only electrical system grounding is the ground ring then you might have a code violation, because your single electrical system ground electrode is being used in lieu of the LPS system grounding.

If you have a setup as @roger describes, where you can identify suitable electrodes for the electrical system and suitable electrodes for the LPS, then I think you are kosher code wise but IMHO should look more closely from a design perspective.

I would be cautious if there are multiple connections between the electrical system grounding and the ground ring, because you don't want any LPS currents to enter the electrical system via one path and exit via another. My completely amateur opinion is that you would want well defined grounding for the electrical system, the ground ring for the LPS, and a single connection jumper between the two.