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I have a box with 2 dimmers and one on/off switch. One dimmer (right dimmer in the picture) has the ground connected to the bare copper wire in the ground box. The left dimmer has the ground wire capped (looks blue). This was done by an electrician. Is it OK to have one of the ground wires capped? This dimmer recently failed. I replaced it and capped the ground the same way and it works. Just want to make sure it's safe and correct. Thanks.box with 2 dimmers

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Updated based on OP's comment that this is a Leviton RNL06-TW.

There are three different things going on here:

  • Green ground - Any green ground wire (i.e., coming out of a switch, receptacle, timer, etc.) should be grounded properly. That can be either to another ground wire or to the metal box (assuming the metal box is itself properly grounded).
  • Generally speaking, all switches should be grounded. They can be grounded via the yoke, as long as they are designed to be installed that way, which is normally the case with a metal plate/yoke as in your switches, and as long as they are installed in properly grounded metal boxes with nothing in between the yoke and the box, again as appears to be the case here.
  • Wires that are not bare copper or green or green/yellow are not ground. If any of those are not needed then they should be capped unless the instructions say otherwise. A typical example is a traveler/communication wire used if a timer is installed in a multi-switch (e.g., 3-way or 4-way switch) configuration.

In this case, the blue green wire should be combined in a wire nut with the other ground wires. Not strictly needed for grounding thanks to the metal yoke + metal box, but definitely best practice.

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    Agree with this. Sometimes colors vary a bit in shade, but a green ground would never be so discolored that it looked blue. The blue would be a traveller. Also, just for the askers benefit... The green screw or ground wire is almost never needed for a device or switch to function. You may never notice a problem, so people assume it's not important, but the ground wire should always be used for safety reasons. They come into play when there is an electrical fault, and then you really want it to be there and working.
    – JPhi1618
    Nov 1, 2021 at 20:22
  • Thanks for the answer and comments. Much appreciated! I can assure you that the wire is green. It's just a different shade and the lighting makes it look blue. Is my best bet a grounding clip? I don't see a yoke or any grounding screws in the box.
    – Tim
    Nov 1, 2021 at 20:34
  • Well, it looks blue to me, and there is a green wire on the other switch and the difference is pretty clear. As far as the yoke - that is the fancy term for the part of the switch that the screw goes through to attach to the box - in both of your switches it is the metal front plate. I wouldn't expect to see any grounding screws - if they supply a ground wire then the expectation is that you would connect it with a wire nut. As far as the blue wire, what is the make/model # of the dimmer so we can check the directions? Nov 1, 2021 at 20:37
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    Thanks again. The model is Leviton RNL06-TW amazon.com/Leviton-R00-RNL06-0TW-Dimmer-White-Almond/dp/… The instructions refer to the "Green dimmer ground lead".
    – Tim
    Nov 1, 2021 at 20:52
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    If you connect the ground wire to the other grounds before working on anything else, then the metal plate on the front of the switch is grounded even when the switch is unmounted and you're working on its live conductors. A small added safety margin that perhaps the original installer of this switch couldn't be bothered with. If the box were plastic it would be essential. In your situation, it's ok to do it the way it was done, though not perfect, and it avoids untwisting and retwisting a bunch of wires that ain't broke. What I would do is untwist them and reconnect them with a lever nut.
    – jay613
    Nov 1, 2021 at 21:33

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