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Old 01-31-2013, 09:16 PM   #1
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Separating Grounds & Neutrals in Subpanels


Hello,
New to the website here. I have a question about subpanels; I understand that they are supposed to have a separate four wire feed, and are not supposed to have the neutral and ground bars bonded. My question is, I have seen a few instances where 3 wires (hot+hot+neutral...no ground) were ran to a detached structure, and a ground rod was driven at this separate structure. In the panels the neutral and ground bars were bonded together. What exactly is dangerous about this situation?

Thanks.

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Old 01-31-2013, 09:24 PM   #2
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Separating Grounds & Neutrals in Subpanels


Those are fine in a detached structure with a separate ground - either a rod or plate in the ground.

Cannot do that with a panel that is bonded from the main service.

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Old 01-31-2013, 09:27 PM   #3
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Separating Grounds & Neutrals in Subpanels


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Those are fine in a detached structure with a separate ground - either a rod or plate in the ground.

Cannot do that with a panel that is bonded from the main service.
That is not true in the US.
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Old 01-31-2013, 09:31 PM   #4
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Separating Grounds & Neutrals in Subpanels


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Cannot do that with a panel that is bonded from the main service.
What exactly do you mean? If four wires (hot+hot+neutral+ground) were run to the structure, they could not be bonded in the sub because the ground could carry current. Is that what you mean?

Or does this mean that any instance where neutral and ground are bonded in the main panel, there can never be a bond in a sub panel?

Thanks again.
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Old 01-31-2013, 09:37 PM   #5
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Separating Grounds & Neutrals in Subpanels


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That is not true in the US.
I had the understanding the CEC was getting closer to the NEC with the changes in 2012....

We can either ground a separate building using a feeder from the main with a separate ground plate or rod OR run the ground from the main service without a separate plate or rod. As long as all the grounding procedures are followed.
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Old 01-31-2013, 09:39 PM   #6
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Separating Grounds & Neutrals in Subpanels


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Originally Posted by Kyle_in_rure View Post
What exactly do you mean? If four wires (hot+hot+neutral+ground) were run to the structure, they could not be bonded in the sub because the ground could carry current. Is that what you mean?

Or does this mean that any instance where neutral and ground are bonded in the main panel, there can never be a bond in a sub panel?

Thanks again.
If you run a bonding wire(ground) to the different structure, you cannot ground the neutral at the subpanel.
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Old 01-31-2013, 09:43 PM   #7
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Separating Grounds & Neutrals in Subpanels


The ground rod does not act as an equipment grounding conductor. The ground rods are for lightening protection. This is why a separate equipment grounding conductor is require for a subpanel. Keep in mind that if the feed to the detached subpanel is in continuous metal conduit (EMT/Rigid), the conduit can act as the equipment grounding conductor. In this case, only three wires would be running to the sub.
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Old 01-31-2013, 09:44 PM   #8
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Separating Grounds & Neutrals in Subpanels


So, there are a couple of structures on my property (a barn & workshop) that have subpanels from the main back at the house; no grounding conductors were run from the main to these subs (only 2 hots and a neutral), and they are not in EMT, grounding rods were driven and neutrals/grounds are bonded at these subpanels. Is there any risk of shock or other fault problems?

Last edited by Kyle_in_rure; 01-31-2013 at 09:49 PM.
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Old 01-31-2013, 09:44 PM   #9
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Separating Grounds & Neutrals in Subpanels


Quote:
Originally Posted by MCB View Post
I had the understanding the CEC was getting closer to the NEC with the changes in 2012....

We can either ground a separate building using a feeder from the main with a separate ground plate or rod OR run the ground from the main service without a separate plate or rod. As long as all the grounding procedures are followed.
In a detached building we are required to run H-H-N-G and utilize a ground rod (I believe it's now two rods.)
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Old 01-31-2013, 09:50 PM   #10
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Separating Grounds & Neutrals in Subpanels


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Originally Posted by diystephen View Post
In a detached building we are required to run H-H-N-G and utilize a ground rod (I believe it's now two rods.)
We've generally gone from the two ground rods 2m apart to a plate. Too hard to get the rods deep enough to meet the requirements in our province, anyway. But you ALSO bring a ground from the main?
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Old 01-31-2013, 10:04 PM   #11
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Separating Grounds & Neutrals in Subpanels


Quote:
Originally Posted by Kyle_in_rure View Post
So, there are a couple of structures on my property (a barn & workshop) that have subpanels from the main back at the house; no grounding conductors were run from the main to these subs (only 2 hots and a neutral), and they are not in EMT, grounding rods were driven and neutrals/grounds are bonded at these subpanels. Is there any risk of shock or other fault problems?
As long as the grounding rods are deep enough to satisfy your local authority for grounding rods/plates/etc, and your boxes are bonded properly, sounds good to me. You are just needing to get a potential fault current to the earth around your structure and bring it up to the same potential without hurting anyone.
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Old 01-31-2013, 10:10 PM   #12
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Separating Grounds & Neutrals in Subpanels


Alright, Thanks again for all the answers.
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Old 01-31-2013, 11:20 PM   #13
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Separating Grounds & Neutrals in Subpanels


Kyle...where are you located? It's obvious that there are some differences in code between the US and Canada and it would suit you well to disregard information form the one which doesn't apply. It's a matter of what is right and wrong, rather than differing opinions. In the states, unless you are doing an electrical remodel you do not have to change existing wiring.
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Old 02-01-2013, 03:08 PM   #14
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Separating Grounds & Neutrals in Subpanels


Located in the states, my main concern was with safety, i.e. I don't want the metal frames of appliances shocking me when I use them.
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Old 02-01-2013, 03:25 PM   #15
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Separating Grounds & Neutrals in Subpanels


Your installations may have been code compliant when they were installed.

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