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I have two light switches in two separate plastic switch boxes. The upper box controls the motor of a fan, and the bottom switch controls some outlets. I want to change the wiring so that the bottom switch controls the light on the fan.

Since the wiring for the fan came into the upper box, I plan to fish new wire from the light in the upper box to the lower box, and connect that to the lower switch.

However, this post says that the new wire must be clamped to the switch box, since it is nonmetallic. Unlike the box in that question, my switch box does not have clamps, and looks like this:

enter image description here

How can I secure the wiring to the switch box?

Edit: Just to be clear, the switch boxes are already in the wall and are connected as described above. I am just trying to modify the wiring. I would rather not remove or replace the boxes if possible.

  • Ecnerwal's comment on Cathode's answer, linking to this question, says you don't have to. However, currently no answer here outlays how to (e.g., cut the wall open). – Mazura May 21 '15 at 22:18
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That box does have clamps. The "flaps" that cover the holes are clamps. You push the cable in, and the clamps prevent it from sliding back out.

  • I thought those flaps were punch-outs (like those on metal boxes) meant to be completely removed and would not serve as clamps. – Dan D. Nov 22 '14 at 8:28
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    Sorry, you are correct. The box you've pictured does have knockouts, not clamps. If you cannot secure the cable within 8 inches of the box, you'll have to replace it with a box that has integral clamps. – Tester101 Nov 22 '14 at 14:22
  • No. The clamps are designed to prevent the cable from being pulled out of the box, so pulling the cable out of the box will be a challenge. If you don't have access to secure the cable, how are you securing the box? – Tester101 Nov 22 '14 at 14:31
  • Use old work boxes. Then secure the cables in them, before you secure the boxes in the wall. – Tester101 Nov 22 '14 at 14:33
  • The boxes were already in the wall before I started. – Ed McMan Nov 22 '14 at 16:12
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NM cable cannot be fished, because it needs to be secured to the framing of the structure within 8 to 12 inches of the box (the "clamps" in the box do not count). Type MC cable can be fished, but will not work with that style of box.

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    There is an exception for retrofit in existing walls. diy.stackexchange.com/a/11636/18078 – Ecnerwal Apr 21 '15 at 19:54
  • NM cable absolutely CAN be fished and, as @Ecnerwal stated, there is an exception for existing walls. However, i still would want to secure it to the box somehow...which is exactly what I'm trying to find out how to do. Since the flaps apparently can break off or cut the cable or are otherwise not very reliable. – Soundfx4 Oct 25 '16 at 18:52
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You can get a dual switch that will fit in a single-gang box. Then you don't need to rewire that bottom box at all. Also, you need to be sure that the top box and fan are wired such that it is possible to separately work the fan and light. A picture of the wires coming into that top box would be useful to confirm the feasibility of this project.

  • Also, @tester101's answer is correct: the flaps will clamp the wire. – djs Nov 22 '14 at 6:46
  • The light and fan motor are on separate conductors (black and red). – Ed McMan Nov 22 '14 at 14:22

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