Overfilling a box

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  #1  
Old 09-03-02, 12:14 PM
G
GasGuzz
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Overfilling a box

My neighbor asked me to check his garage wiring (he's adding more outlets).
He has an existing 18 cu.in. single box where he installed a comb Switch/GFCI-outlet. The Switch is feeding another GFCI-protected branch downstream. There is another circuit going through this same box (using the box as a splice junction point).
I've accordioned the wires/splices to the back and installed the SW/GFCI device, and there is no significant resistance against the device (there are 6 wire nuts behind there).
I've pointed out the 15A/14-2 loads and this is not in question.
I say it's ok, I don't think you can PHYSICALLY pack a box (without deforming it).
Is this ok?
Thanks.
 
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  #2  
Old 09-03-02, 01:21 PM
G
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I'm afraid you can over pack a box without deforming it. there are rules as to how many wires are allowed in a box. How many wires are in there and what size of wire are they?

Each wire entering the box is counted against the box fill. if six wire nuts are already in use in the box you may be over the limit already. Number 14 wire is calculated at 2.00 cubic in and number 12 is 2.25 cubic in the device counts as the same as a wire. so if you have an 18 cubic inch box and number 14wire then the device is 2.00 in this would allow you to have eight other wires in the box and still remain in code providing they are all the same size if any wire is larger then the device is sized off of it and not the smaller wires. Other considerations are connectors for the cable that are on the inside of the box are also counted.

Let us know exactly whats in the box and then we can be specific
 
  #3  
Old 09-03-02, 01:29 PM
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GasGuzz
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Gard:
Please define a "wire"? All the circuits here are 15A/14-2 NM-B. Do you call 14-2 as 1 or 3 wires?
 
  #4  
Old 09-03-02, 01:48 PM
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GasGuzz
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Ok, I called my neigh to verify and here’s the deal (I remember seeing 6 wire nuts before I reconfigured it up).
There’s a circ/splice passing through = 2-14/2 wires, 3 wire nuts. 1-14/2 wire feeding the SW/GFCI device, and 1-14/2 wire feeding downstream (from this device). So we’re looking at 4-14/2 wires into this 18cu.in. box.
 
  #5  
Old 09-03-02, 02:54 PM
J
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The required minimum is at least 8*2+2+4 = 22 cubic inches. 2 more if cable clamps are used. Larger boxes are cheap.
 
  #6  
Old 09-03-02, 03:03 PM
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GasGuzz
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1. "8*2+2+4 " - Huh?
2. There's a 22 cu.in. single box?
3. The larger box is beside the point. What's given is that the EXISTING box is 18 cu.in. and drywalled.

Thanks.
 
  #7  
Old 09-03-02, 07:28 PM
J
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1. 8 wires times 2 cubic inches per wire, plus 2 cubic inches for the grounding wires, plus 4 cubic inches for the receptacle. Any good book on home wiring will tell you how to compute the required volume for any situation. There are a lot of factors.

2. Yes, 22.5 cubic inch single-gang plastic boxes are commonly available.

3. It's not that hard to replace the box without damaing the drywall. Pry the box away from the stud and replace with a 22.5 cubic inch old work box. Even if you do damage the drywall, drywall repair is not rocket science.
 
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