How many wires can a box hold?

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Old 04-22-05, 03:58 AM
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Smile How many wires can a box hold?

I have a 32 cu-in double gang box (the deepest box I can get from HomeDepot) that will hold 2 3-way switchs, now that there are 6 cables entering this box:

2 12/3 cables for the 3 way switches
2 12/2 cables going to the lights controled by these switches
1 12/2 cable for power feed
1 12/2 cable brings power to the receptacle box underneath this box

My questions is can all these wires fit in the box? Thanks.
 
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Old 04-22-05, 04:08 AM
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By my calculations you have exceeded box fill requirements.

My suggestion is to run the wiring differently.
 
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Old 04-22-05, 04:23 AM
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Can you please give me some more details on how the box fill requirement is calculated? Thanks.


Originally Posted by racraft
By my calculations you have exceeded box fill requirements.

My suggestion is to run the wiring differently.
 
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Old 04-22-05, 04:25 AM
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You would have the equivalent of 19 wires in this box. Each switch counts as 2 conductors and the ground would count once.

19 x 2.25 = 42.75 cu. inches.
 
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Old 04-22-05, 08:38 AM
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The technical info for volume calcs can be seen here
As someone who just had the same problem, I will tell you what the experts here at the forum suggested, if you can make it work....
Run power to lights first, then 12/2 to each of your other 3-way switches - then a single 12/3 to each 3-way at your referenced box is all you will need to provide a loop between each of the two sets of 3-ways.
One item that folks seemed to have different opinions on was whether to add a conductor count for the internal clamps (even though they're skimpy) that are present in the 2-gang box. Since the manufacturer's info says to count it, I did. This would bring your total conductor count to 20.
 
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