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I am replacing an old dimmer switch with no ground wire with a dimmer switch that has a ground wire.

The metal box in my wall is grounded, but there is no ground screw or anywhere else to attach the ground wire from the switch.

Is it safe to simply cap off the wire, or should I remove it from the dimmer box? Even if it is capped off, the insulated portion will be touching other wires inside box due to limited space.

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    Is there a hole in the back of the box that is tapped for a ground screw?
    – ThreePhaseEel
    Commented Aug 26, 2018 at 2:02
  • Is this a regular single pole dimmer, or some sort of fancy dimmer? Can you get a dimmer with a self-grounding clip on it?
    – ThreePhaseEel
    Commented Aug 26, 2018 at 4:15
  • It's a single pole dimmer.
    – jkaw
    Commented Aug 26, 2018 at 5:56
  • The dimmer may require the ground connection to power itself. Read the instructions and see if ground is permitted to be left disconnected.
    – Harper - Reinstate Monica
    Commented Aug 26, 2018 at 18:26
  • The instructions don't specify. But the dimmer appears to work without the ground connected.
    – jkaw
    Commented Aug 27, 2018 at 1:42

2 Answers 2

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Use a grounding clip to attach the ground wire to the grounded metal box.

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  • The box is in the wall very tightly and I'd rather not manipulate it to add a grounding clip. There is also very limited room inside the box so I'm reluctant to leave the ground wires exposed. To be clear, I'm not asking how to ground the wires to the box, I'm asking if it is ok to cap off the wires and leave them inside.
    – jkaw
    Commented Aug 25, 2018 at 23:41
  • Is this a ground wire lead from the switch that you are wondering about? Or is it the coiled grounds from the house wiring? The switch must be grounded to comply with code. It would not require any manipulation of the box to slip the ground clip onto the outer edge. If you don't want to buy a whole pack of these clips you could get a ground screw into an existing hole or drill one.
    – Jim Stewart
    Commented Aug 26, 2018 at 2:02
  • It's the ground wire attached to the dimmer unit - so yes, the lead from the switch. According to code (this has been referenced in a few other posts), if you are replacing an ungrounded light switch, you don't need to ground it as long as you have a noncombustible cover. I'm simply replacing what was already there except the new switch has a ground lead and nothing to attach to. I just want to know what I can do with the lead wire, hence my question: can I just cap it and leave it in the box?
    – jkaw
    Commented Aug 26, 2018 at 3:14
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Drive a ground screw into the back of the box and then attach the ground wire to that

You can get a fine-pitch, self-tapping ground screw (Garvin GSST or equivalent part) and drive it into the back of the box even if there is no tapped hole there, then simply attach your ground wire to the screw.

If you're using the Code provision that allows an ungrounded switch with an insulating faceplate...

...then simply cap the ground wire off with a wirenut, then.

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    Thanks for the edit to the comment. Should I be concerned with the insulated ground wires (assuming capped) touching other wires in the box? I've seen elsewhere people talk about removing the ground lead from the light switch altogether.
    – jkaw
    Commented Aug 26, 2018 at 5:58
  • It is very common for insulated wires (even the un-insulated ground) to be in contact in a box.
    – Jim Stewart
    Commented Aug 26, 2018 at 11:02

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