Grouonding a subpanel

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  #1  
Old 12-17-05, 08:23 AM
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Grouonding a subpanel

I've installed a sub panel in my detached garage. It is fed from a 60amp breaker in my house service entrance panel. The sub panel ground and neutral busses are not bonded. I drove an 8' X 5/8" copper rod into the ground and attached it to the sub panel ground bus with AWG 6 copper stranded. How can I tell if this single rod provides an adequate ground for the sub panel?
 
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Old 12-17-05, 09:37 AM
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You would need a special meter, that is not worth buying. The code permits you to drive a second rod and connect it, then no further integrity testing is required.
 
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Old 12-17-05, 11:03 AM
EricT
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ground loop

One thing I would check- if your main panel has its own ground (I am sure) and you are connecting the ground wire between the main and sub, and you provide a ground rod to the sub as well, you could create a ground loop condition. These are bad. In essence - if there are 2 paths to ground for an outlet, say your ground rod on the sub panel, and the ground rod on the main panel, then potential will flow.

I just installed a sub panel for my hot tub - ran 6-3 plus ground, and connected the ground the whole way. So that way there is only one path to ground - no loop.

I am not an electrician, but I used to install large battery backup systems in large datacenters, and the lengths gone to prevent ground loops was staggering. I have even seen a ground halo run around the entire room before - now that was some getup.

Make sure you dont have a possible ground loop condition - real electricians please chime in and beat me up here if I am the least bit off.

Eric
 
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Old 12-17-05, 01:06 PM
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The NEC requires a Grounding Electrode at a seperate, detached stucture.

Ground-path concerns arise if the Feeder does not provide an Equiptment Grounding Conductor.
 
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