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Old 06-11-2019, 02:24 PM   #1
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Grounding sub-panel in detached garage/shop.


A few years ago I purchased a place that has a garage/shop that is detached from the house. The outbuilding has a 100 amp panel with 6 slots...only 4 of which were being used, so I decided to put in a 40 amp 240-volt breaker to power a welder.

While doing this, I noticed that, while the ground bar was connected to a ground stake to the left side of the panel location, the neutral bar is only connected to the 6/4 wire coming from the main service. I noticed a second ground stake to the right of the panel with nothing connected.

My question is, was the unused ground stake intended to be connected to the neutral bar in the panel, and if so, does it need to be completely insulated from the panel?
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Old 06-11-2019, 02:52 PM   #2
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Re: Grounding sub-panel in detached garage/shop.


You NEVER want to ground/bond a neutral in a sub-panel.
Your neutral in the 6/4 is connected to the neutral bar in the main panel, which is providing the neutral/ground bond.

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Old 06-11-2019, 02:56 PM   #3
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Re: Grounding sub-panel in detached garage/shop.


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Originally Posted by codger View Post
A few years ago I purchased a place that has a garage/shop that is detached from the house. The outbuilding has a 100 amp panel with 6 slots...only 4 of which were being used, so I decided to put in a 40 amp 240-volt breaker to power a welder.

While doing this, I noticed that, while the ground bar was connected to a ground stake to the left side of the panel location, the neutral bar is only connected to the 6/4 wire coming from the main service. I noticed a second ground stake to the right of the panel with nothing connected.

My question is, was the unused ground stake intended to be connected to the neutral bar in the panel, and if so, does it need to be completely insulated from the panel?
Unless you have a separate electric meter for the shop, you have a sub-panel in your shop. In a sub-panel the ground and neutral are kept separate. Do not connect the neutral to the other ground rod.
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Old 06-13-2019, 04:47 PM   #4
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Re: Grounding sub-panel in detached garage/shop.


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Unless you have a separate electric meter for the shop, you have a sub-panel in your shop. In a sub-panel the ground and neutral are kept separate. Do not connect the neutral to the other ground rod.
Yes, I should have said "sub-panel" in my post. I helped my friend (a licensed electrician) when he re-worked the main panel in the house a few years ago, and I remembered that the neutral was "bonded" to the ground there. For this sub-panel, I wasn't sure and (sadly) I couldn't ask my friend because he had passed away about a year ago.

Thanks for the help.
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Old 06-13-2019, 05:14 PM   #5
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Is the panel fed by 3 or 4 wires? Is there a metallic path between building s?
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Old 06-13-2019, 08:29 PM   #6
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Subpanel in separate buildings from the service that are fed with 3 wires are again bonded like a service.
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Old 06-14-2019, 09:11 AM   #7
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Re: Grounding sub-panel in detached garage/shop.


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Subpanel in separate buildings from the service that are fed with 3 wires are again bonded like a service.
So are you saying if it's a 4 wire, then that implies a ground wire and so you wouldn't bond the ground and neutral? (because the ground becomes a parallel path with neutral?)

And I'm guessing with 3 wire, that implies a lack of a ground wire, so you have to bond the neutral and ground (to rod or ufer) since you have no ground there otherwise.

Just trying to understand this. I would have thought the bonded subpanel, even though only 3 wire, would create a parallel path through the grounding system through the earth to the main panel. Maybe more resistance, but I would have thought it possible.
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Old 06-14-2019, 10:16 AM   #8
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Technically you are right about the neutral possibly feeding thru the earth, but it should no be of concern as long as you do all wiring as specified by common practices and codes. No separate ground to the garage requires you to bond to the neutral, provide a ground rod, and ground to any other existing grounding locations such as metallic water pipes or metal building frame.
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Old 06-14-2019, 01:35 PM   #9
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Re: Grounding sub-panel in detached garage/shop.


From post#1,
Quote:
While doing this, I noticed that, while the ground bar was connected to a ground stake to the left side of the panel location, the neutral bar is only connected to the 6/4 wire coming from the main service. I noticed a second ground stake to the right of the panel with nothing connected.
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