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I am replacing 1 of the 2 dimmer switches in a double gang box. I'm replacing the right switch in the picture. The new dimmer switch (Lutron smart switch) has 3 wires, which includes the ground wire. But as you can see in the picture, the old switch on the right only has two wires coming out and no ground.

My question is: What is the best way to handle the ground in the new switch?

The junction box isn't metal and doesn't seem to have anywhere to connect the ground wire.

Apologies for the basic question, I'm super new to wiring and I've read the ground isn't super important, but I just want the correct/safest answer!

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  • Can you post a photo showing where the wiring enters the box please? – ThreePhaseEel Apr 12 at 0:36
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    Sure looks like a metal box, if so the screw that holds the switch to the box should serve as a ground, assuming the box is properly grounded. as ThreePhaseEel said, More info please. – Alaska Man Apr 12 at 0:46
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    My mistake, metal indeed! I attached another photo, but not sure if it helps at all. I see a metal screw that holds the junction box in place against the wall - I guess that could be used? – user1960089 Apr 12 at 1:05
  • The yoke of the switch bottoms out on the box flange when you screw it in, right? – ThreePhaseEel Apr 12 at 1:07
  • Some terminology in there I'm not familiar with. But once the switches are screwed in, the metal yoke of the switch sits flush on a wooden frame you can see in the pics, and does not touch the metals box – user1960089 Apr 12 at 1:17
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You don't need to do anything. The switch will pick up ground via the screw heads of the mounting screws. (this "via the screw heads" trick does NOT work for receptacles).

If you really want to attach the ground wire, then find the screw hole in the back of the box that is tapped 10-32. That is specifically for a ground screw. You can't use screws tasked with some other purpose. You can drill and tap your own #10-32 hole, or you can use a grounding clip on the edge of the box. Of course you don't have to do any of these things for a switch or self-grounding receptacle.

Now, that thing you're doing with the wood blocks is not allowed. You cannot make a "box extension" out of wood, because the job of a junction box is to contain fires from electrical arcing. Wood would only accelerate such a fire.

I gather you have been using wood screws to mount the switches on the wood; instead use 6-32 screws to mount it to the metal. Further, you will need a metal box cover so the box is fully encapsulated in metal.

If you really, really need the switches to sit prouder than that, you can either rework the box with a taller "mud ring", add a Legrand Wiremold Surface Conduit Starter Box as a 1" box extension, or add something like a Hubbell PTC200GY switch extender, which is made to be a weatherproof outdoor cover for switches (but if you only use it as a spacer, I won't tell :)

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  • There is also the option of a CISBEX, which is designed for exactly this sort of millwork depth problem. There is a plastic version too although I'm having trouble remembering the name. – K H Apr 14 at 10:15

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