Feed Subpanel with NM cable, no conduit?

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  #1  
Old 09-21-06, 01:09 PM
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Feed Subpanel with NM cable, no conduit?

I'm adding a 125 Amp subpanel next to my main panel. Can I feed the subpanel with 6-3 NM without conduit? This is in-the-wall wiring, between studs.

The 6-3 has a smaller guage ground wire, 10 guage I think. Should I run a bigger wire to link the subpanel ground to Main panel ground?
 
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Old 09-21-06, 01:17 PM
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If the wall will be drywalled or if the cable is above 6'6" from the floor, then it is allowed. You can use up to a 60A breaker in the main panel to feed the sub with 6/3 NM-B. The #10 ground is acceptable.

If this is a short distance, why not use a stub of 1-1/4" EMT conduit panel-to-panel and #2-2-2-6 THHN copper feeders for the full 125A? The price won't be that much higher if you're only buying 10 feet of wire for example. For the small increase in price, you will have the ability of using the subpanel to its full capacity and your loads in the subpanel will experience less voltage drop.
 
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Old 09-21-06, 01:42 PM
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Thanks. Yes, the wall will be sheetrocked.

I'll consider the 2-2-2-6 cable. I already have the 6-3 NMB cable and a 60Amp breaker from a previous spa installation. I'm basically adding new "required" dedicated circuits for a kitchen remodel. The actual power load will be light.
 
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Old 09-21-06, 03:06 PM
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If you do go with the 1-1/4" EMT conduit 125A route, I meant that you should use 4 individual THHN wires of sizes #2 (black),#2 (black), #2 (white), and #6 (green). You can find this type of wire by the foot at nearly any home center or electrical supply house. I should have been more clear in my description; the ratings for NM cables are different than the ratings for individual wires in conduit, so precision matters in this case.

Even if you choose to use the 6/3 cable with 60A breaker, I think you should consider installing the 1-1/4" conduit. If you need 125A in the future, you wouldn't need to remove any drywall. Simply swap the #6 NM with #2 THHN and the 60A breaker with a 125A.
 
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Old 09-21-06, 03:58 PM
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OK. I'll use the EMT conduit.

Yes, I misunderstood the 2-2-2-6, I thought you meant an NM-B bundled cable. For individual #2 THHN wires, would both hot mains be Black, or should one be Red?

Maybe I can put the 50 feet of 6-3 NM-B to other good use, running a 240VAC line out to my garage. The price of copper wire sure got expensive!
 
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Old 09-21-06, 07:10 PM
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The hot wires can both be black. The only advantage of using different colors is to tell them apart. But in this case it doesn't matter.
 
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Old 09-22-06, 08:40 AM
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The #2 hots can be any color other than white, grey or green. I said black because most big box stores will only carry black in that size. If they don't carry white for the neutral, you can use a black wire and wrap the last six inches of each end with white electrical tape to "re-identify" the wire as white. Likewise, you can tape one of the hots red if you prefer it to be identified.

The only wire that cannot be re-identified is the ground wire. It must be green or bare, but you should have no trouble finding #6 in green or bare.
 
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Old 09-23-06, 11:15 AM
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Just so we're clear a number six neutral must have a continuous outer covering that is white or grey and a number six or smaller Equipment Grounding Conductor must be green or bare. Only wires larger than number six can be marked at there terminations with tape, paint, labels and so forth.

200.6 Means of Identifying Grounded Conductors.
(A) Sizes 6 AWG or Smaller. An insulated grounded conductor of 6 AWG or smaller shall be identified by a continuous white or gray outer finish or by three continuous white stripes on other than green insulation along its entire length.
...
(B) Sizes Larger Than 6 AWG. An insulated grounded conductor larger than 6 AWG shall be identified either by a continuous white or gray outer finish or by three continuous white stripes on other than green insulation along its entire length or at the time of installation by a distinctive white marking at its terminations. This marking shall encircle the conductor or insulation.
 
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Old 09-23-06, 03:10 PM
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Originally Posted by kbright
...I already have the 6-3 NMB cable and a 60Amp breaker from a previous spa installation. ...
I realize it doesn't matter anymore, but are you aware this previous spa was wired wrong? NM is not allowed for spas.

Just keep that in mind if you get another one.
 
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Old 09-23-06, 05:39 PM
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NM is not allowed for spas OUTDOORS. It is perfectly acceptable indoors.
 
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Old 09-24-06, 03:20 PM
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Originally Posted by racraft
NM is not allowed for spas OUTDOORS. It is perfectly acceptable indoors.
Duh. I guess I knew that. I wasn't thinking. Sorry. I've done a lot of spas and not a single one was indoors. It just never occurred to me it might have been indoors. Belay my last, and thanks for the correction.
 
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Old 09-24-06, 03:36 PM
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Doesnt matter whether the spa is outdoors or indoors if the spa is outdoors the cable can be nm-b up to where it transitions to the outdoors. Kind of nit picky but just a clarification.

Roger
 
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