Cargo container ground?

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Old 12-11-08, 12:04 PM
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Cargo container ground?

I'm putting a subpanel on my 40 foot metal cargo container. It sits on the ground. Can I use it as my electrical ground for my new plugs, etc.?
 
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Old 12-11-08, 12:51 PM
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In my opinion it would be treated the same as a steel-framed building which means that it must be bonded to the panel ground bar, but it cannot be used as an equipment grounding conductor itself. However if you install the branch circuits using metal conduit like EMT, IMC, or rigid steel, those conduits can act as grounds. You will also need to install grounding electrode(s) outside of the container such as an 8' copper rod.

Could you explain the project a little more so we can get a better idea of what rules apply? Will this be a workshop, residence, storage area, etc? How will it connect to a mains power supply?
 
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Old 12-11-08, 08:24 PM
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I've run an underground 10/2 cable from my main panel to a subpanel on my container. This will be my workshop. I'm hoping to have 120volt and 240volt for a welder off the same 10/2 cable. Rather than drive a ground rod into the ground I was just wondering if the metal container could act as such since so much metal is in contact with the ground.
 
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Old 12-11-08, 08:27 PM
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The subpanel should have been feed with a 4 wire feed, 2 hots, 1 neutral and 1 ground. With 10-2 you can only have 120 circuits to your shop.

Yes you need the ground rod. Sitting on the ground is no substitute.
 
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Old 12-11-08, 08:31 PM
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What size welder (amps). #10 may not be enough.
 
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Old 12-11-08, 10:45 PM
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I have 2 welders, a 120v and a Lincoln 240v. I'm seeing now that with 10/2 wire already run (and I don't want to dig it up), I'll have to be satisfied with 120v on everything. That will work for me as I don't do that much welding. Just thought I could get 240v service out of it. Obviously I'm not a professional in this area, just trying to save a few bucks.

Thanks for everyone's input.
 
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Old 12-11-08, 10:49 PM
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And yes, I'll pick myself up a ground rod.
 
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Old 12-11-08, 10:57 PM
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Grounding

You need to be careful. If you don't ground your container correctly somebody could touch that metal container and get electrocuted. You should drive an 8' ground rod and or if you have a copper waterline going out there that should also be connected to the ground. If you don't you can bury 20' of #4 bare copper. Than you want to tie or we call it bond, all these connections together at the ground bar in the panel. DON'T TIE THE GROUND AND NEUTRAL TOGETHER!!! Unless this will be a main panel, instead of a sub panel. They only place you tie the ground and neutral together is at the main. The ground wire is sized per the current or wire you are useing to feed the sub panel in the container.
 

Last edited by Old electricin; 12-11-08 at 10:59 PM. Reason: to add info
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Old 12-12-08, 10:26 AM
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Originally Posted by lochness View Post
Just thought I could get 240v service out of it. Obviously I'm not a professional in this area, just trying to save a few bucks.
With XX/2 cable you can get 120V circuits or 240V circuits, but not both. With XX/3 cable you can get both 120V and 240V circuits.
 
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Old 12-12-08, 02:29 PM
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Thanks guys! I appreciate the help and info.
 
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