In Reply to: Re: Are you referring to... posted by Todd Krieger on April 2, 2007 at 23:45:15:
Todd:How is it different? They're purposely isolating the ground at that receptacle (note the little "x" on the Romex ground meaning "cap off") and using a separate ground electrode (single rod in this case). The only difference is that a single electrode is one rod or plate, and a grid is comprised of more than one rod or plates.
We (electrical consultants) do this kind of design all of the time for isolated instrument grounds in industrial and institutional applications. The trouble (in a residential installation) would be to find the code rule that permits one to have an isolated ground electrode in the first place. I don't think this would be allowed - I think you would be forced to interconnect multiple electrodes using standardized methods, thus defeating the purpose of having an I.G. in the first place.
One heck of an idea, and it would work for having a ground with a lower noise floor. The question is: is it allowed? And if it IS allowed, would the inspector want a GPR (ground potential rise) test done on that one single electrode? My guess is that if he was open minded enough to allow a separate electrode for an I.G., he'd want to see a GPR test - and the extra testing, the report and the extra time for the additional inspection would all come out of the homeowners pocket, and rightly so.
The diagram shows the concept only. It does not show how to calculate or test for the GPR of the electrode, and it definately does not discuss the ramifications one could encounter when it comes time to have such an installation inspected.
Cheers,
Presto
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Follow Ups
- Re: Are you referring to... - Presto 11:57:14 04/03/07 (3)
- Re: Are you referring to... - gbeard 12:01:55 04/04/07 (2)
- It makes a very interesting statement about separate ground rods too!! - Presto 12:41:45 04/04/07 (1)
- FWIW, acording to BOTH articles, it's a code violation. (nt) - Presto 13:53:02 04/04/07 (0)