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.
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.