House Has No Ground Wires

[Oakley]

I'm replacing existing Lutron dimmers in an old house with Caseta dimmers. I discovered that the green screw on the existing dimmers isn't connected to anything. The other three wires are the same color. The wall box is metal. Should I simply cap off the green ground wire on the Caseta dimmer and otherwise install per the instructions? I would assume this would still work and would be as safe as what I have currently, but I'm no electrician. I would very much appreciate guidance.

[FlyingDiver]

Are there ground wires in the wall box? They'll be bare copper with no insulation. If so, connect the green terminal on the Caseta to them.

[Oakley]

No, there is no bare copper ground wire.

[Zach R.]

I'm replacing existing Lutron dimmers in an old house with Caseta dimmers. I discovered that the green screw on the existing dimmers isn't connected to anything. The other three wires are the same color. The wall box is metal. Should I simply cap off the green ground wire on the Caseta dimmer and otherwise install per the instructions? I would assume this would still work and would be as safe as what I have currently, but I'm no electrician. I would very much appreciate guidance.

Yes, simply cap the green wire on your Caseta device.

[AJF4ME]

Since you have metal boxes it sounds like your house is wired with BX cable; the type of cable that has a metal sheathing. In that case the metal sheathing acts as a ground.

[Lukeetal]

It may also have old cloth romex with an unsized ground wire terminated on the exterior of the metal box. Grounding the dimmer to the box is the best option. It may also be possible to attach a ground tail to the metal box and connect it to the dimmer. Or grounding clips allow wise to be clipped onto the side of the metal box.

[SparkyCoog]

Since you have metal boxes it sounds like your house is wired with BX cable; the type of cable that has a metal sheathing. In that case the metal sheathing acts as a ground.

Many older houses have metal boxes and still have either knob and tube wiring or the old cloth NM cable without a ground. I seriously doubt this house has a proper ground - unbroken bonding to the panel, connected bonding jumper at the panel, and a ground rod. Never assume grounding just because there is a metal box.