In Reply to: Re: Are you referring to... posted by gbeard on April 4, 2007 at 12:01:55:
Gbeard:Thanks for posting that. Good info.
"For safety purposes, you can't run an IG equipment-grounding conductor in its own conduit or outside the branch circuit or feeder conduit. You also can't terminate the IG equipment-grounding conductor to a lone ground rod."
Ha ha ha. I need to call a code inspector or two on this one. Some people are saying inspectors will approve the separate rod. Some, including the author of the article you mentioned, say NO WAY!
In any case, we're not just running an I.G. here - we're doing what the article says NOT to... we're talking about having a separate electrode (or grid) for the I.G..
I checked back into some earlier designs where we did separate grids for instrumentation. We used a "ground connection junction box" for the "derived" ground - the isolated conductors from the instrument ground grid, the isolated conductors TO the instrument grounds, AND the bare condcutors from the local ground grid ALL are connected at ONE SINGLE POINT. The junction box is only used for isolating the various grids for TESTING purposes - it is never in service with the grids isolated from one another.
The scheme on page 8 of the referrenced document we have never done and never would do. The two grids need to be TIED TOGETHER to remain at the SAME POTENTIAL. You CANNOT use earth to connect these two grids (or rods) together for the reasons already pointed out. (Potential differences, ground potential rise, etc.).
Cheers,
Presto
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Follow Ups
- 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)