Ground Rod Inside Building

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al

Senior Member
Is there any Code requirement that a supplementary rod electrode cannot be located inside a building? Example would be a house with a crawl space with a dirt floor.
 

dereckbc

Moderator
Staff member
Re: Ground Rod Inside Building

I do not believe there is any restriction that says it has to be outside. I see them inside of commercial and industry.
 

charlie

Senior Member
Re: Ground Rod Inside Building

No problem, sorta. The Code is a permissive document, in other words, if it doesn't say you can't, then you can. In the case of a ground rod in the crawl space, how do you deal with the dryness issue in the future when the soil dries out? I know the rod extends down about 10 feet (length of the rod plus the depth of the crawl space), but I would think it would still be dryer than the surrounding area. Remember the Code is a minimum standard. I would not feel comfortable with the idea. :(
 

bphgravity

Senior Member
Re: Ground Rod Inside Building

There is no restriction as long as you meet the requirements of 250.53(D)(2) and (E), (G) if supplementing underground metal water pipe, or 250.54 and 250.118.
 

al

Senior Member
Re: Ground Rod Inside Building

Charlie: In this case the rod would be an additional 4' below outside grade due to the crawl space depth and next to the foundation outside wall. Becuse of this I believe the ground resistance would be less in this case.
Al
 

karl riley

Senior Member
Re: Ground Rod Inside Building

By chance I found an answer to this from Charlie Trout (Code Message of the Day) from 2000. He says it is allowed but questions why you would want to direct a lightning strike to that point. He adds that driving two rods might save time rather than having to prove a 25 ohm resistance from the rod in dry soil.
Karl
 

wocolt

Member
Re: Ground Rod Inside Building

Are we talking supplemental electrode or supplementary electrode there is a difference.
ie, supplemental electode 250.56 and suplementary grounding electrodes and their conductors are not required to comply with the bonding requirements of article 250.50/
Supplementary electrodes are usually used for signal reference 250.54.

WOC
 
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