Subpanel detached garage commons

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Old 04-04-10, 08:19 AM
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Subpanel detached garage commons

I have read the the "bond" in a subpanel should be broken and the commons should be floating with the ground in a ground bar and attached to a grounding rod. My question is if it is OK to just tie all the commons together, without the bar and tape the crap out of them.
 
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Old 04-04-10, 08:29 AM
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Tape is not a substitute for a good conection. Explain your situation more fully and perhaps we can help.
 
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Old 04-04-10, 08:47 AM
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OK, I'll try to explain. 3 wire (black,red,white) plus bare copper ground to subpanel box that has one grounding bar to attach ground wire. I think I need to attach another bar inside the box to attach the commons, and since the commons and grounds need to be seperate at the subpanel, can I just leave the grounding bar that is inside the box and run a bare copper to a grounding rod. Instead of adding a floating bar for the commons can I just tie them all together and not attach them to anything inside the box?
 
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Old 04-04-10, 09:22 AM
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I am going to assume when you say commons you actually mean the neutral conductors. If this is so, there should be a bar already in the panel to accept them. One per hole in the bar. Taping them together is not correct.

You may need to add a grounding bar for the green or bare conductors.
 
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Old 04-04-10, 09:26 AM
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If you're installing a new subpanel, there is a neutral bar. I have yet to see any panel, new or salvaged, without a neutral bar. It is possible that this is already bonded to another ground bar. It is more likely, however, that the ground bar is seperate and must be assembled to the panelbox. This is far more common. If you are using some salvaged panel without a neutral bar, please purchase a new panel with the proper equipment.

If both bars are present, you must remove the linkage between them in a subpanel. If only the neutral bar is present, the ground bar will be assembled by you.

You should not tap the feeder neutral directly to the branch circuit neutrals without utilizing the neutral lug and neutral bar provided. It would be an extremely inconvenient and subpar installation. I would highly discourage it. Given some time I believe I would be able to find a code violation in it, but the truth is you just shouldn't do it so I'm not going to waste time searching the NEC for why.

You may use a bare conductor for your grounding electrode conductor to the ground rod. If you are running it without conduit, the code requires it be sized at 6 AWG. If there are any metal waterpipes in your garage, you should also run another grounding electrode conductor to them and bond them as part of your grounding system for the building.
 
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Old 04-04-10, 10:09 AM
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3 wire (black,red,white) plus bare copper ground to subpanel box that has one grounding bar to attach ground wire.
What you are calling a "grounding bar" is probably the neutral bar you are looking for.
 
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Old 04-04-10, 10:42 AM
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Does what you are calling the ground bar set on plastic insulators? If so it is the neutral bar.There may be a bonding screw through it or as previously mentioned a bonding strap that needs to be removed.
 
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Old 04-04-10, 01:51 PM
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RHefferan hit the nail on the head. Hes totally correct on this one. You only bond and the 1st means on disconnect(Main panel) and indeed the neutral bar should be there. If its new the grounding bar is prob in the box still. If not go buy one or hire a competent person to do this. Have you checked with your local city ordnance and codes to see if its even legal for you to install this?? You prob need to have a permit pulled....
 
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Old 04-04-10, 02:53 PM
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Thanks for the clarification. It is a neutral bar, I will have to install the grounding bar seperate. I thought it was the other way around, but the neutral bar is insulated from the box.
 
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