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Old 11-06-2010, 09:04 PM   #1
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grounding of a barn

I'm wiring an all metal barn. The structure is based on poles cut from 6" pipe from an old pipeline set vertically on 10' centers around the perimeter. Each pole is set in the ground about 3 feet and set in concrete.
C Channel is welded horizontally between the poles with H panel siding.
The lower C channel forms the outside of a reinforced concrete floor, the concrete poured against it. Solid rock is at about 3 feet. Soil is often very dry. Can I use the metal building itself as a ground rather than a copper rod? Or maybe the question is, would not the building itself be a better ground than a ground rod?




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Old 11-07-2010, 09:45 AM   #2
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Ayuh,... While I agree the building is No doubt well grounded,...
I'd still drive a grounding rod, at an angle if necessary, for the electrical entrance...


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Old 11-07-2010, 10:16 AM   #3
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If you are running a feeder from another structure or having a new service installed, the ground rod is required. This rod is connected to the building and panel via a solid copper conductor sized for the service or feeder.
Check out all the threads on this subject as it has been beat to death here. This is by far the most common type question asked on this forum.
At the top use the search function. You will get all the information you need to do this compliantly and safely. Good luck.
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Old 11-07-2010, 12:18 PM   #4
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Barn wiring

Thanks ya'll for the replies. I'll use a ground rod connected as suggested. I had seen some reference in the 250 section of using the building itself as the ground but was unsure, and I've had trouble in this rocky, dry ground with effective ground rods before.

The main panel has been in place for years without any ground other than the ground wire from the pole to the box. I discovered this while adding on to the building. Now I also need a sub panel.

With a ground rod properly connected to the main box and the building frame, the subpanel should have a seperate bus bar for the auxiliary grounds which is grounded to the box and building framework only and not the neutral bus bar. Correct?

Also, if the subpanel is fed through a 100 amp breaker in the main box (not much else to come from), is it ok to go through another 100 amp breaker at the subpanel just to have a shutoff at that location?

Thanks again,
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Old 11-07-2010, 04:45 PM   #5
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a building foundation can be an effective ground. In fact, it is better than a rod and was designed because of your situation. Arizona, dry ground; ground rods were ineffective. Mr. Ufer came up with the idea of using the foundation for a grounding electrode/ 250.52(A)(3)

there is also the metal frame of the building or structure, which sounds like your building might fill the bill. that would be 250.52(A)(2). If your building conforms to the requirements detailed in the code, it would be an adequate grounding electrode and it would not require a supplemental electrode, including a rod.
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