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Old 11-24-2007, 08:41 PM   #1
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240V circuit on 8-2w/ground


situation:

Shed about 110 feet from 200 amp main panel in house. 8-2 w/ground run from panel through enclosed ceiling, out of foundation and then buried to shed, no conduit, direct bury wire.

Would like to run 240 V circuit to the shed. Can I use the ground as the neutral and install a ground rod at the shed to pick up the ground? Add and bond a ground bar and seperate the neutral? What would the max voltage be for the size and run? Load in the shed would be all 110V, 15 and 20 amp circuits for power tools, lights, small low amp compressor etc etc.......

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Old 11-24-2007, 09:48 PM   #2
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240V circuit on 8-2w/ground


If you have no other metal paths like water pipe or phone line between the house and shed then the three wire feed is code compliant. A ground rod is required in any case.

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Old 11-24-2007, 10:12 PM   #3
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240V circuit on 8-2w/ground


NO. If I am not mistaken the ground wire is uninsulated. That is your first problem. You DO NOT bond the neutral on a sub panel. It is not a seperately derived system. The ground rods are required for a detached garage but you do not bond them. You could take the other hot leg and use it as a neutral (provided you change the connection at the main panel). I don't know if you need 240 out there but this is not the way to do it.
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Old 11-25-2007, 12:52 AM   #4
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240V circuit on 8-2w/ground


Joe is correct you are allowed 3 wire feeders to outbuildings. You also bond the neutral and ground see NEC 250.32 (B)(2) 2005. and as Joe stated only if there are no metallic paths between the buildings. When your area adopts the 2008 code cycle you will no longer be allowed 3 wire feeders. Grounded conductors (NEUTRAL) in an underground feeder are to be insulated.

Second image is for a 4 wire feeder
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240V circuit on 8-2w/ground-3-wire-feeder-detached-building.jpg   240V circuit on 8-2w/ground-4-wire-subpanel-detached.jpg  

Last edited by Stubbie; 11-28-2007 at 02:05 AM.
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Old 11-25-2007, 08:37 AM   #5
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240V circuit on 8-2w/ground


You CANNOT use the bare ground in an 8/2 cable as a neutral. If you are feeding an outbuilding with just three wires, the neutral must be insulated. A ground rod will NOT "pick up the ground" as you state.
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Old 11-25-2007, 08:41 AM   #6
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240V circuit on 8-2w/ground


Quote:
Originally Posted by HouseHelper View Post
You CANNOT use the bare ground in an 8/2 cable as a neutral. If you are feeding an outbuilding with just three wires, the neutral must be insulated. A ground rod will NOT "pick up the ground" as you state.

The 8-2 is probably romex anyhow...
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Old 11-25-2007, 10:16 AM   #7
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240V circuit on 8-2w/ground


Quote:
Can I use the ground as the neutral


8-2 w/ground generally has a bare ground so....no.
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Old 11-25-2007, 12:36 PM   #8
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240V circuit on 8-2w/ground


All as I thought: yes the ground conductor is bare, and no metal in the ground other than the wire between shed and home, there is a black yard pipe water line between house and shed.

I guess I will just have to revert to the 110V circuit, I was just trying to max out the available power.

Can someone confirm the max amp capacity for me, different sites and reference materials give different capacities. Would love to feed with a minimum 40 amp SP so I end up with 30 at the shed.

I appreciate all the assistance.

Last edited by jjkeswick; 11-25-2007 at 12:39 PM.
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Old 11-25-2007, 01:06 PM   #9
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240V circuit on 8-2w/ground


40A is the max.

Andy

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