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Old 03-06-2011, 11:14 AM   #1
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Garage Subpanel Wiring Question


Iím in the middle of wiring a 50amp subpanel in my attached garage for a welder and compressor (they won't be used at the same time so 50amp is sufficient). I have a couple of questions about using NM-B cable:

I plan to run about 30í of 6-3 Romex (NM-B) cable along the floor joists in the basement from the main panel to an existing opening in the wall between the basement and garage. For physical protection going through the wall and into the subpanel, Iíd like to remove the outer PVC jacket of the cable and run the three wires (plus ground) in ĺĒ EMT conduit for approx. 6í (see pictures below). Iíll use an EMT to Romex fitting or bushing to transition. Iíve read that NM-B uses THHN wires, so is removing the PVC sheathing for a 6í run like this ok to do?

On the same subject, I also need to continue running #6 wire in a conduit from the subpanel to an outlet in the garage. Iíd like to use the remaining NM-B cable since Iíll have some left over, but I donít want to try to run cable through a conduit. It seems like I should be able to remove the PVC jacket and run the wires individually, but the wires arenít individually labeled as being THHN, so I donít know if this is ok to do.

Everything will be inspected before the final connections are made, but any advice would be appreciated. Thanks




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Old 03-06-2011, 11:50 AM   #2
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Garage Subpanel Wiring Question


I would put a junction box at the end of the conduit, with all of the appropriate clamps and fittings to admit the Romex cable and from there run the wire ends minus the sheath into the conduit.

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Old 03-06-2011, 11:51 AM   #3
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Garage Subpanel Wiring Question


The conductors inside NM type cable are not labeled as to their insulation and cannot be stripped of the overall sheath and used in conduit as you propose. You can transition in a junction box to individual conductors or continue the conduit to the other panel.
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Old 03-06-2011, 12:23 PM   #4
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Garage Subpanel Wiring Question


Thanks for the replies. What you said about the rating of the wires makes sense for the sub-panel to outlet run, but I just want to be clear about the run between the main panel and sub-panel.....it would be a continuous run with the 6' of individual wires clearly belonging to the cable. So you're saying that the wires that belong to the cable aren't rated for individual use? Thanks
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Old 03-06-2011, 12:46 PM   #5
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Garage Subpanel Wiring Question


why not run a bigger conduit and not strip of the sheathing?
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Old 03-06-2011, 12:58 PM   #6
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why not run a bigger conduit and not strip of the sheathing?
That's probably what I'll end up doing, step up to 1" or 1 1/4" and run the full cable through. That'll teach me not to start working before asking the questions
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Old 03-06-2011, 01:25 PM   #7
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Garage Subpanel Wiring Question


Why not run the cable direct to the panel. It does not look to be 'subject to damage' being that high up on the wall.
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Old 03-06-2011, 01:37 PM   #8
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Garage Subpanel Wiring Question


I'd put a junction box right there at the end of that last 90 and transition to your romex right there. BTW, there is nothing saying that you cannot run the romex in conduit, either sleeving for protection (24" or less before derating) or through the entire run. You must calculate conduit fill by using the widest dimension of the romex. 6-3 is round anyway though.
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Old 03-06-2011, 02:21 PM   #9
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Why not run the cable direct to the panel. It does not look to be 'subject to damage' being that high up on the wall.
I'm more concerned about where the cable goes through the wall. I don't want the Romex contacting the edge of one of the cinder blocks.

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I'd put a junction box right there at the end of that last 90 and transition to your romex right there. BTW, there is nothing saying that you cannot run the romex in conduit, either sleeving for protection (24" or less before derating) or through the entire run. You must calculate conduit fill by using the widest dimension of the romex. 6-3 is round anyway though.
1" EMT gives the right fill if I use the cable so that seems to be the best solution. The run from the sub-panel to the outlet is another 30' around the garage walls, so at this point I'm trying make the most of the cable I already have.
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Old 03-06-2011, 02:56 PM   #10
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I would put a junction box at the end of the conduit, with all of the appropriate clamps and fittings to admit the Romex cable and from there run the wire ends minus the sheath into the conduit.
This would not be Code compliant. The cable is listed as an assembly. Stripping the outer sheath removes the listing as the condictors are now unidentified as to type.
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Old 03-06-2011, 03:14 PM   #11
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Garage Subpanel Wiring Question


Simply install one of these on the end of your conduit, and you're all set!


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