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# Integral Box Clamps

#1
08-03-05, 06:47 AM
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Integral Box Clamps

Does code allow inserting more than one NM cable through one of the integral clamps in a multi-gang plastic box?

I have a 3-gang old-work box I planned to use, but it only has 6 openings and I have 7 cables I wanted to feed into it. Thanks.

#2
08-03-05, 11:20 AM
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Do you only have three total, or are there six on top and three on the bottom? If you run out of space on the top you need to bring the wire to the bottom and loop up into the box. Make sure your wires go on the side of the box and not behind it.

If all the spaces are used up then you may be over box fill.

#3
08-03-05, 12:16 PM
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There are 3 openings on top and 3 on the bottom, so six total. I figured I would have to loop some of them around to the bottom, but wanted to put 7 into the box (3 switches in the box, so 3 wires out to sets of lights, 2 wires to other 3-way switches, 1 power in, and the 7th would be a central vac outlet hook-up wire because I don't have any other 15-amp source near by).

The box is 55 cu. in., so if I calculated right, I can fit all that in. And I can physically fit 2 wires into 1 opening. But I thought I read somewhere you can only put 1 wire per opening.

#4
08-03-05, 02:10 PM
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Why aren't you running the power to the light from the other three way switch from each pair of three way switches? That would reduce the number of cables into this box to four (while adding one cable to the box for each of the other three ways). Unless the other three way switches are much further from the lights they power, that would seem more practical, and would make this box much cleaner.

#5
08-03-05, 03:15 PM
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In one of my previous iterations of my wiring plan I was feeding at least one of the light sets from the other 3-way switch in one of the pairs, but those boxes are just as messy and I think would have been over-full too (they both also contain another 3-way switch on a different circuit for the other side of the basement - I'm trying to modify from what the builder already had in place).

But thanks for the suggestion, and I will look at it again and see if I can come up with a better compromise. Seems like every time I do, I keep finding a little better way of doing it.

As a last resort (and if the answer to my question was "no"), then I'll just find a different source of 15-amp power to tie the central vac outlet into (the vacuum guy said it was OK to wire it into a 20-amp circuit, but its 14 gauge wire, so I assume he was wrong?).

#6
08-03-05, 03:25 PM
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As a last resort (and if the answer to my question was "no"), then I'll just find a different source of 15-amp power to tie the central vac outlet into (the vacuum guy said it was OK to wire it into a 20-amp circuit, but its 14 gauge wire, so I assume he was wrong?).

I read right past the vac before...

I would think that the central vac should have its own circuit. If you have it sharing a circuit with lights, you are probably going to see some serious light dimming when the vacuum is used. Is the vacuum cord and plug connected, or direct wired?

#7
08-03-05, 03:49 PM
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You cannot have a 20A breaker if any piece of the circuit is #14. You really should run a 20A homerun for the vacuum in a minimum of #12.

I don't have a code book in front of me but on multi-gang, plastic boxes you can only have 1 wire per entry. Only with single gangs can you pair up the wires. I don't think there are any other exceptions. (Please correct if wrong.)

Most plastic boxes I've worked with have plenty of entries for wires (which is why I said if you used them all you might be over box fill). You might just try looking for a different brand of box.

#8
08-03-05, 09:30 PM
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The main vacuum unit will have its own circuit - I was just referring to the electrical connection for one of its remote outlets, just for turning the brush roll on the attachment wand that plugs in.

Thanks for confirming only 1 wire per opening. I did pick up a "new work" box that has 12 openings. Since I have access to the back from the adjacent unfinished side of the basement, I'll just see if I can nail it in without wrecking the drywall around it.

#9
08-04-05, 08:32 AM
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If you can't get a hammer in there, you can use a large C-clamp to force the nail into the stud.

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