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wilco3 05-20-2010 08:37 AM

Need some clarification on subpanels. I am moving my overhead 100ampservice (at the house) to underground 200amp service(at my detached garage). I will then install a new 200amp panel in the garage and feed my existing 100amp panel (at the house). So, my existing panel at the house will now be a subpanel.
I need to understand the proper grounding for this set up. And also any necessary seperation of ground and neutrals (rules that usually apply to main and subpanels in the same structure).

kok328 05-20-2010 02:48 PM

You'll need to ground the sub to the main and a ground stake at the sub wouldn't be a bad idea either. The sub panel must have the ground & neutral bar separated in the sub panel. A sub panel doesn't necessarily have to be in the same structure to be considered a sub panel. A sub panel doesn't necessarily have to be a secondary panel off the main panel either. A panel that is downstream of the main service between a disconnect is actually considered a sub panel.

JoeD 05-21-2010 08:04 AM

In your situation you need to ground the new panel in the garage. It needs ground rods and the neutral and ground bonded together. The existing main panel in the house needs to be converted to a sub panel. The neutrals and grounds need to be separated. The neutral needs to be unbonded from the panel. You need a four wire feed from the garage to the house. The existing ground rods at the house need to stay.

triple D 05-27-2010 12:20 AM

the rods......
assuming there is rods on a 100 amp service is a longshot. I'm guessing one 6 footer if any. He will need two galvanized 5/8" diameter 8' rods at both panels. Check your local code for proper spacing. Good luck...

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