Electrical for Shed - Ground bar needed at the shed?

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Old 10-05-16, 11:28 AM
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Electrical for Shed - Ground bar needed at the shed?

Hi! I had some questions about the proper way to run power to my shed, from my house. I plan on trenching the PVC conduit (18 inches deep) and running NM-F underground cable, 12 gauge. I purchased 2 GFCI breakers rated for 20 amps (I know, way overkill, I only need 1), 1 for the main breaker panel in my house and 1 for the shed subpanel I purchased.

I understand the wiring of the GFCI as opposed to a traditional breaker, but my question is related to grounding. Do I need a separate ground rod at my shed to ground the subpanel? I was told that I cannot connect the neutral/ground to the same bar in the subpanel, as that wasn't up to code.

Thanks in advance for your help!
 
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Old 10-05-16, 12:19 PM
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For a single circuit feed to a shed you do not need a ground rod. You do need a separate ground bar for the grounds if you install a panel. If it just goes to switches and receptacles you do not.

A 20 amp single pole switch can be the disconnect.
 
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Old 10-05-16, 12:21 PM
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You really shouldn't have a panel for single 20A circuit, all you should have is a single disconnect switch after the cable enters the building. A simple heavy-duty switch or air conditioner style pull-out disconnect is adequate. Having two GFCI devices is more likely to cause problems. One is preferred.

If you do install a panel, it needs a separate ground bar, to have the neutral bond removed if it comes with one, and you also need to install a ground rod which is bonded back to the subpanel ground bar.
 
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Old 10-05-16, 04:04 PM
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Thanks for the replies! The question I have however is that if i use the subpanel ( which i understand is unnecessary, but I already have it installed in the shed), in the power feeding it from my main circuit breaker, the ground wire is tied into the ground bar in the main panel, which is also shared with a neutral. How can I get a separate ground for the shed panel?

I will remove the second GFCI and only have one then, most likely in the main circuit breaker panel.

Could it hurt to put another ground bar in near the shed and run a dedicated ground wire over to the shed panel?

Also, I have a GFCI outlet tester. IT does not trip the GFCI breaker when it's hooked up, but the GFCI test button (on the breaker itself) does trip the circuit. Any thoughts on why that might be?
 
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Old 10-05-16, 04:43 PM
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Panels don't normally come with ground bars. They must be bought and added. No bonding screw or strap is used at the neutral bar. But make this simple and don't use the panel. Return it and get a 60 amp non fused air conditioner pull out disconnect.
Example: http://www.homedepot.com/p/GE-60-Amp...0RCP/100674085
Could it hurt to put another ground bar in near the shed and run a dedicated ground wire over to the shed panel?
Do you mean rod. Yes, if you use a panel it is code required but it would be a GEC not an EGC. GEC is for atmospheric charges to reduce the chance of lightning strikes. EGC is your ground wire on the branch circuits that is used to clear faults when a hot shorts to a metal chassis.

Final note. Your subpanel is almost certainly for 120/240 not 120 so you can only use half of it. The lugs where you connect incoming power are probably not rated for wire as small as #12 so yet another reason not to use the panel. If you do you probably will need to use pigtails of a size equal to the smallest permitted wires for the lugs.
 
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Old 10-05-16, 07:00 PM
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I will follow your advice and return the Subpanel and buy the non-fused disconnect.

When I hook this up correctly, should my GFCI tester that plugs in my outlet trip the GFCI breaker?

Thanks for your help.
 
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Old 10-05-16, 07:25 PM
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I plan on trenching the PVC conduit (18 inches deep) and running NM-F underground cable, 12 gauge.
No such thing as NM-F cable. There is NM-B cable which cannot be used outside at all and there is UF-B cable which is direct burial rated and doesn't need to be in conduit. If you want to use conduit you should abandon the idea of cable and do it right by pulling in THHN/THWN-2 conductors.
 
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Old 10-05-16, 08:00 PM
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I'm sorry, I misspoke, I meant UF-B direct burial cable. Thanks!
 
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Old 10-05-16, 08:14 PM
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I meant UF-B direct burial cable
That is harder to pull. Best to use individual conductors (THWN) as suggested by Joe, one black, one white, one green. If you think you might at sometime need more power also pull a red. That way if you ever need more power you can convert to a multiwire circuit with out using a panel and have two 120v 20a circuits..

You will not need a ground rod at the shed.
 
 

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