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I have an existing standard light switch that controls a single two-plug outlet. I would like to replace the switch with a dimmer switch.

The dimmer instructions expect two black wires and two white wires (and a ground) in the box, but there is only a single white and a single black (and a ground). The white wire and black wire come from the same larger white wire, where the first layer of sleeve has been removed to show the two of them.

How do I wire this up correctly?

Instructions enter image description here

Wall Box enter image description here

Dimmer Switch enter image description here

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  • Is there NM cable available with two black wires and one white plus bare ground? Aug 4 at 23:07
  • @JimStewart -- nope, no such thing exists Aug 4 at 23:40
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I have an existing standard light switch that controls a single outlet. I would like to replace the switch with a dimmer switch.

You can't

It is a code violation to put a dimmer on a receptacle.

Because, you (or the next guy) could plug any appliance in there, and some appliances like to burst into flame when dimmed.

If you really, really have to do it, then one company makes special sockets for that purpose. They are keyed to reject normal plugs. They will accept a special plug, which you then install on your lamp. The special plug is able to plug into normal sockets.

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  • 1
    That's assuming "outlet" is being used in the typical non-NEC meaning of "the thing where you can plug stuff in" as opposed to the NEC meaning of "anything that gets electricity". Which (the typical meaning) is 99.99% likely to be the case. Aug 4 at 15:01
  • 2
    Just wanted to add that the special sockets and plugs that you mentioned (Lutron HDTR/DDTR receptacles and the RP-FDU plugs) were allowed in the 2014 NEC (406.15), but the 2017 NEC removed that section and now states in 406.14: Rating and Use of Switches. Switches shall be used within their ratings and as indicated in 404.14(A) through (F). (E) Dimmer Switches. General-use dimmer switches shall be used only to control permanently installed incandescent luminaires unless listed for the control of other loads and installed accordingly.
    – stmp945
    Aug 4 at 15:11
  • We have a wall switch dimmer on a porcelain screw base light fixture which has a pull chain and integral 120 V receptacle. I used to plug in the power supply of a notebook computer into that receptacle. Occasionally I would forget it was plugged in and would dim the light. I wonder if that was the cause of failures in those power supplies and in USB chargers? Aug 5 at 0:41
  • Do dimmers output full rms input voltage when they are set at full on? Do they distort the input sinusoidal waveform when they are are set at full on? Aug 5 at 10:04
  • @Jim yes they do, unless they have a bypass. Aug 5 at 17:14

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