Questions on new subpanel for garage.

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  #1  
Old 08-05-13, 06:24 PM
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Questions on new subpanel for garage.

I am installing a 100 amp subpanel in my attached garage to provide power for a new workshop. I have a couple of questions. I've mounted the subpanel in my wall, leaving it stick out 5/8" to allow for sheetrock. I then mounted a plywood board between the studs above it to make it easier to run the new cable throughout the garage. Most of the cable will be run overhead so I felt this allowed for better spacing or the cabling entering the subpanel. See the attached picture. Is this acceptable? It will all be covered with sheetrock eventually.Name:  IMG_20130805_174339.jpg
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Also, as I said I will be making most of the runs in the overhead. This is partially below a bedroom and so I will be going through floor joists. There is currently fiberglass bat insulation in between these joists. Should I remove this, install my wires, and replace it? Or can I just run the cables below the existing insulation (making sure to backset the holes in the joists of course.) Also, I will be crossing a 6" round heating duct. What provisions do I need to make for that? (See my second picture). Again, this will all be sheetrocked once the wiring is inspected and complete. Any help would be appreciated. Thanks.Name:  IMG_20130805_182039.jpg
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EDIT - sorry pictures are out of order but you should get the idea...
 
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Last edited by BakaNeko59; 08-05-13 at 06:27 PM. Reason: pictures
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  #2  
Old 08-05-13, 07:07 PM
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Welcome to the forums!

That should be just fine. I find though, that installing a 2x4 between the studs is easier to nail to than plywood. The other thing to think about: Is the plywood set so that the nails of the staples will not poke out the back side of the wall?

If it was me, I would remove the insulation, install the cables, then reinstall the itch back in. This will also give you more room to go around the round duct.
 
  #3  
Old 08-05-13, 08:25 PM
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The face of the plywood, or any nailer, needs to be recessed ~2" from the face of the studs, to protect the cables. It looks like you may have done that.

The cables overhead should be run + centered top to bottom of each joist. You can cut the facing on each batt and cut up into the insulation to do that, then tape the facing back together.

Here's a suggestion, though: If your garage/workshop is not conditioned space and the bedroom above it, of course, is, then I would want to install insulation with the vapor retarder up, not down. Or install unfaced insulation.
 

Last edited by Nashkat1; 08-05-13 at 09:38 PM.
  #4  
Old 08-06-13, 07:27 AM
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I then mounted a plywood board between the studs above it to make it easier to run the new cable throughout the garage.
I think you'll soon regret having the plywood above the panel, you'll have a hard time driving a cable staple into it. I assume the sheet rock on the ceiling, under the bedroom, will be fire rated.
 
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Old 08-06-13, 05:03 PM
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Yes I mounted the plywood back so that cables running down it are in the center of the stud.

I wondered about the insulation (which side for the facing). However that's the way I found it. I do plan to insulate and rock the rest of the garage when I'm all done (5/8 fire rated), so hopefully that won't be a problem.

And the plywood is held in place by 1x1 firring strips behind it mounted to the studs so it's pretty solid. Shouldn't be any problems getting staples into it.

Lastly, I plan to put 15 amp outlets in the ceiling for plugging in lights rather than hardwire the lighting. Do I have to use the round ceiling boxes or can I use standard nail-in rectangular ones? And is there any problem running 12/2 wire for a 15 amp circuit as long as the breaker and outlets are also 15 amp? I have a lot of 12/2 and don't want to have to buy a whole roll of 14/2 just for my lighting circuits.

Thanks for the help.
 
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Old 08-06-13, 05:29 PM
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Use the rectangular boxes for the ceiling receptacles.

#12 can be used on a 15 amp circuit. If you change to a 20 amp breaker you will get 1/3 more capacity for the same cost.

The latest NEC states that ALL, including ceiling mounted receptacles, be GFI protected.
 
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Old 08-06-13, 07:06 PM
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And is there any problem running 12/2 wire for a 15 amp circuit as long as the breaker and outlets are also 15 amp?
15 amp duplex receptacles can be used on a 20 amp circuit.
 
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Old 08-06-13, 07:36 PM
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15 amp duplex receptacles can be used on a 20 amp circuit
Correct for U.S. NEC. CEC, Canada, may vary.
 
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