Connect the Ground?

I am wiring up Gen2 dimmers and on/off switches in a newer house wired with standard 3 conductor romex (live/neutral/ground).

The ground wire isn’t indicated in the wiring diagrams. But the dimmer has a green screw suggesting it can be grounded.

What did you do? Did you just connect the ground to the fixture, bypassing the switch? Did you ground the switch? Any idea why the ground is left off the wiring diagrams? Is there any downside to connecting the ground to both the switch and the fixture it controls?


Utilize the ground. It’s there for safety reasons and should also be connected to switches and end devices. Yes, there are some older switches that didn’t support earth ground, but newer ones do have it and should be used.

I believe they weren’t captured in the drawings because it would add more lines to the drawings and “crowd” the important Wires shown. I think there’s a note saying ground not shown but should be connected.

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The ground you are referring to is the equipment ground or safety ground. In new construction it is likely a bare wire.

The equipment ground should be connected to the Green screw on the dimmer and similarly the green screw or bare wire on the fixture (if it is metal).

The reason it is not shown on the diagrams is the equipment ground goes to everything and would needlessly obfuscate the functional wiring. In addition, some older houses have no bare wire for equipment ground but use the metal box as a safety Ground. You likely have a blue or gray plastic box.

It would probably be a good idea to address these conditions in some sort of note.

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@JohnRob @datavortex - Found it in the manual.

Look under wiring key & rpo tips, third bullet. Also, there is a Note: under the romex wire in the drawing.

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Thanks @harjms, I missed it.

The electrician here told me they never connect the ground to the outlet itself. The reason is because all our box are metal and are grounded. So when screwing the outlet to the box, the box become grounded. He would only connect the ground in a plastic box.

The part where he is worried, is the fact the Inovelli metal frame is painted black, which might reduce it conductivity to use the frame of the light switch as the ground source… I haven’t seen any details about this so far.

That coating is not conductive. So he is correct that the switch won’t self-ground. However, you can remove that coating with a dremel or other roto-tool. It will take about a minute.

Also, unless there is something weird in Canada, there shouldn’t be any reason you can’t physically ground the switch if you don’t want to grind the coating. The “never do it” is probably they usually don’t do it because the devices self-ground. At least in the US, we simply ground the switch with a pigtail. The metal box will have a screw hole. Insert a grounding (green) screw and attach a length of bare copper. I can’t imagine how this would be against code, but I don’t know the CA code. Pigtailing a ground should take about 2 minutes. (And this is exactly how it’s done if you have to use a plastic spacer on a metal box.)

TBH, grinding off the coating ought to get it. Either way, no reason not the by Inovelli because of the coating.

Okay here’s the deal.

You want the switch to be grounded.

If the switch is in a METAL enclosure, and the ground wires are attached to the enclosure with a screw, the switch is grounded. Yes the switch is painted- but the inside of the screw holes will make enough contact to give a ground. If you want to test this, get a multimeter in continuity mode, with one probe scratch the paint a little, with the other probe touch the metal box. You can also hook up the ground wire- there’s no harm in doing it.

If the switch is in a PLASTIC enclosure, obviously no grounding happens through the screws. In a plastic enclosure, you must connect the grounding screw.

While the switch will ground on the screw, since the mounting hole is larger than the screw diameter, it is possible to mount the switch where you would not have contact between the screw and the conductive surface of the switch, hence no ground. So to insure a proper ground, scrape or grind off the coating or use a pigtail.

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