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07-30-2012, 07:04 PM   #1
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## Receptacle Box Capacity

Hello all! I have a question that I can't seem to find the answer to. I am wiring a bedroom and am trying to determine if I can wire a receptacle and junction out to another receptacle box and an exterior motion light. Basically, I want to feed a deep single gang receptacle box for the receptacle. My question is can I then junction out to another receptacle down the wall about 8 feet, but also junction up to an exterior motion light? Can all of these wires be in a deep box? I do not understand how the NEC calculates number of conductors and air space. I understand it, but it doesn't satisfy me with my question of whether I can do this or not.

This is in a bedroom that is in the corner of my house adjacent to the front sidewalk.

Last edited by crater13bravo; 07-30-2012 at 07:06 PM.

07-30-2012, 07:13 PM   #2
"So I Re-Wired It"

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Calculations based on cubic inches of box and wire guage. NEC Table 314.16(b)

22.8 cu in. non-metallic box using 14/2 wire = 11 conductors.
count 2 for wiring device, 1 for each colored wires, 1 for clamps (if needed), all grounds combined =1

if im not mistaken

Last edited by MisterZ; 07-30-2012 at 07:21 PM.

 07-30-2012, 09:06 PM #3 Lic Electrical Inspector     Join Date: Dec 2009 Location: The Great Police State of New Jersey Posts: 1,826 Rewards Points: 1,108 Plastic or metal? Wire size? __________________ All responses based on the 2011 NEC. If you live in New Jersey click here. All other states click here. Please check with local, county and state officials as laws may vary. Sizing motors here. Online motor calculator here. Online calculators here.

 07-30-2012, 09:14 PM #4 Newbie   Join Date: Jul 2012 Posts: 2 Rewards Points: 10 Metal 2x3x3-1/2. 12-2 with ground
 07-30-2012, 09:27 PM #5 "So I Re-Wired It"     Join Date: Nov 2011 Location: NorthEast USA Posts: 258 Rewards Points: 250 I believe it is 8 conductors. 2 for thedevice box - 1 for each insulated wire - 1 for all grounds
07-30-2012, 09:49 PM   #6
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Quote:
 Originally Posted by crater13bravo Metal 2x3x3-1/2. 12-2 with ground
Your box is not big enough.
3 whites
3 blacks
1 all grounds
2 device
1 clamps

10 conductors

Box is rated for 8 conductors
__________________
All responses based on the 2011 NEC.
Please check with local, county and state officials as laws may vary.
Sizing motors here. Online motor calculator here. Online calculators here.

Last edited by electures; 07-30-2012 at 09:52 PM.

07-30-2012, 11:57 PM   #7
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Quote:
 Originally Posted by electures Your box is not big enough. 3 whites 3 blacks 1 all grounds 2 device 1 clamps 10 conductors Box is rated for 8 conductors
12 gauge wire is a factor of 2.25, so given all the numbers above, you need a box with a minimum of 22.5 cu in.

 07-31-2012, 12:08 AM #8 "So I Re-Wired It"     Join Date: Nov 2011 Location: NorthEast USA Posts: 258 Rewards Points: 250 Switch to plastic. They are a bit larger, and no need to ground the box
07-31-2012, 12:12 AM   #9
Lic Electrical Inspector

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Quote:
 Originally Posted by MisterZ Switch to plastic. They are a bit larger, and no need to ground the box
The deep plastic box is 20,5 cu in. Since there are no clamps it will work.

__________________
All responses based on the 2011 NEC.
Please check with local, county and state officials as laws may vary.
Sizing motors here. Online motor calculator here. Online calculators here.

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