Sub panel without a ground

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  #1  
Old 04-21-12, 04:21 PM
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Sub panel without a ground

I bought a house last year and it has a sub panel in the basement. There are only three wires coming into the panel. I know that sub panels are to have separate ground and neutral bars however mine does not. I would like to completely replace the panel and add the ground. What size and kind of wire should I use for the ground. The sub panel is wire to a 50amp breaker at the main panel.
 
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Old 04-21-12, 04:47 PM
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#10 ground, bare or green, should be adequate. The existing hots and neutral should be #6 or larger. Is that what you have?

Note the current panel is probably grandfather so not absolutely necessary to add the ground but it does make it safer.
 
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Old 04-21-12, 04:57 PM
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How can i run that wire to the sub panel? can I just staple it to the floor joyce? or does it need to be run in a conduit?

Existing wire is labeled as NM 8-3T

Ya I think the home inspector mention thing being grandfathered in on a few things...
 
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Old 04-21-12, 06:03 PM
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You could use THHN/THWN wire as you suggest stapled to a joist. Wire must run all the way back to the main panel. If exposed to damage at any point sleeving in conduit for protection in the area of exposure would be advisable but is not required. You will probably need to add a ground bar. All grounds need to be moved to the ground bar. The neutral bar is probably bonded to the panel. If so the bonding screw or strap will need to be removed to isolate it.
 
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Old 04-21-12, 11:19 PM
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I'd just ty-rap the ground to the original cable for ease-of-identification.
 
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Old 04-22-12, 05:20 AM
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Justin Smith
I'd just ty-rap the ground to the original cable for ease-of-identification.
I would do that but it runs through my attic, which has 18" of blown insulation, and down a exterior bedroom wall.

The main panel is on the far wall of the garage. So I plan on running it up into the attic above the garage,which has no insulation, and the down the wall between the garage and house and into the basement the just along the joyce.
 
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Old 04-22-12, 07:57 AM
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Just to clarify, if you use NM-B cable, it can be stapled to the joists. If you use individual THHN/THWN conductors, they need to be pulled through conduit.

Typically, NM-B is your best bet. Much easier to install than conduit.
 
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Old 04-22-12, 09:25 AM
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Since the THWN is being used as a ground I'm not sure Zorfdt answer is correct. I think he thought we were talking about running power to the box but I could be wrong.
 
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Old 05-01-12, 09:01 PM
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I was picturing you re-running a whole new feeder (#6/3 w/ground) to your new panel.

As Ray mentioned, if you plan on just adding a THHN/THWN ground, you can do as Ray described.
 
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