Fastening NM-B cable at plastic box

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  #1  
Old 10-05-15, 06:49 PM
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Question Fastening NM-B cable at plastic box

How do you clamp nmb if you are adding a wire to a nail-in box with no clamp?
 
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Old 10-05-15, 07:08 PM
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You staple the NMB cable to the stud just outside the box.
 
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Old 10-05-15, 08:11 PM
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The wire needs to be secured within 8 " of the box .
 
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Old 10-06-15, 08:08 AM
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Right but you can't do that if you are adding a wire to such a box after the drywall is closed up.
 
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Old 10-06-15, 08:18 AM
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Normally it's not required to staple cable in inaccessible spaces when remodeling.

Just use your best judgment as far as keeping cable within wall cavity and drilling studs in center.
 
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Old 10-06-15, 08:26 AM
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After the drywall is installed you need to use what is called an "old work" box that has built-in clamps to hold the type NM cable.
 
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Old 10-06-15, 09:22 AM
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Right, and if you are running a wire to that winged box from a nail-in box, how do you clamp the wire at nail-in box end?
 
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Old 10-06-15, 09:30 AM
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Exactly what box are you using ? Most boxes now, and for quite some while, whether plastic or metal have come with some type of wire retention clamp.
 
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Old 10-06-15, 09:36 AM
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Plastic single gang nail on boxes only have a knockout tab. There is no clamping built in. The OP is adding a cable to an existing box and is looking for how to secure the cable to the existing box.
 
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Old 10-06-15, 09:46 AM
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pcboss understands the question.
 
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Old 10-06-15, 09:55 AM
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The "proper" way would be to remove the original nail-in box and replace it with an old work box. In the real world I doubt that anyone would get excited over a wire fished to an existing box that is not clamped in or near the existing box. I suppose you could add some silicone sealant right at the entry of the cable if you were really concerned.

While there ARE valid reasons for securing wires and cables in switchboards and Motor Control Centers in commercial and industrial work, (the wires and cable do have a tendency to "jump around" due to magnetic forces when applying and disconnecting large currents) I think it is much less necessary in residential work where most circuits are 20 amperes or less.
 
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Old 10-06-15, 10:01 AM
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The "proper" way would be to remove the original nail-in box and replace it with an old work box.
+1 for that. The second reason is I find it a lot easier to fish the cable. Those with patience can do it with out making a hole elsewhere. I just have never even tried and since I can't patch Sheetrock worth a darn I always remove the box. The pros can do it though with out opening the wall or removing the box so your mileage may vary.
 

Last edited by ray2047; 10-06-15 at 11:01 AM.
  #13  
Old 10-06-15, 10:02 AM
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If you replace the original nail-in box with a box with clamps, wouldn't the existing stripped conductors get damaged when pushing through the clamp?
 
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Old 10-06-15, 10:10 AM
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the existing stripped conductors would get damaged when pushing through the clamp.
Not true with plastic old work boxes. Done it more times than I can count but never a problem. Metal old work boxes are not needed for NM cable and are seldom used but have clamps that are screwed down after the wires are inserted so no problem with those.

If this is cloth covered NM that is badly deteriorated it needs to be replaced or sleeved with heat shrink tubing. In any case the clamps can be held out of the way while the wires are inserted.
 

Last edited by ray2047; 10-06-15 at 10:59 AM.
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