I went to install a dimmer switch yesterday. Turns out the old switch didn't have a ground wire attached. I checked another switch. Same thing. The house was built in 1991. I thought a ground wire was required by the building code?

Anyway, a friend suggested I connect the ground wire on the dimmer to the metal switch box to ground it. Does this sound right?

 

No, not unless the friend verified the box is grounded before suggesting that. If your house is wired with non metallic cable the box is not grounded in a circa 1991 house.

What is your wiring method, conduit or cable?

 

I'm not sure. I know next to nothing about electrical wiring. Here's a shot I took of the switch box.

 

That is a plastic box with NM-B cabling with ground. The ground is there.... just painted white.
Carefully pull out the wirenutted cables and look for two single copper wires combined in a wire nut.

 

You can scrape the paint off with your nail to find the bare copper or insulation colors.

 

Ok, thanks. The box is actually metal. There's just so much paint on it, it's hard to tell. So once I find the ground, I assume that I wirenut all three ground wires together?

Is it common for an installer to put in light switches without attaching the ground wire? Seems very lazy to me. Also, should I go through the entire house and attach the ground wires? There's got to be 20-30 light switches alone. I haven't checked any of the outlets yet.

 

If the box is metal and the cover plate is not metal it is optional but best practice is to connect the ground.

(In my area the devices are sometimes installed bu day labors hired by contractors. They are paid by the device not by the hour. Not connecting grounds means less time per device and more devices connected at the end of the day therefore more pay at the end of the day which makes it more likely they will be hired for the next day.)

 

You may have self-grounding switches. Is one of the mounting screws held in place by a small spring wire or a springy metal clip?

 

Are you sure that box is metal ? I can see the plastic molding marks on the back of the box.

 

I think it's stamped metal. I could be wrong. I'll open it back up this weekend when I have time. And daylight.

I also think I see bare copper on the wire furthest back, so that must be the ground wire. Just so I know I know what I'm doing, I remove the cap, trim the two wires and put a new cap on with the ground wire from the new switch. Correct?

 

60+ year old eyes through trifocals, but looks to me like it might be a plastic box with a metal extender.

 

See arrow in picture. This looks like the grounds.