I installed this dimmer in my bedroom https://i.stack.imgur.com/YR6mq.jpg But when I removed the old switch I only found 2 black copper wires connected to the switch. I proceeded to connect this to the black wires in my dimmer switch and it is working. However, I am concerned about the safety of it. Is connecting only the black wires safe? I did cut out the green wire and made sure they connecting parts are covered with electric tape.

Here is a picture of how it looks now:



I replaced the dimmer with one that have the screwed to hold the wires. It also have a grounding green screw as in the image below. pic of updated switch

I still can't tell if I need to attach anything to the green screw. In my apt, look like it's the same namely there is not grounding wires for those switches so I'm assuming the metal box is grounded.

  • Was it installed into a metal box?
    – JPhi1618
    Oct 7, 2019 at 17:50
  • You may have a ground as I've seen on some older homes the wire did have a ground but the switch didn't have a ground connection so the installer just cut the ground off at the sheathing. Oct 7, 2019 at 17:58
  • You need to connect that green wire to the metal junction box. Look way in the back of the box and see if there's a green hex-head screw. Wiring that uses armored cable ("AC") uses the metal cable sheath as the ground. Some people call that BX cable, but that was a brand name, like Kleenex. Oct 7, 2019 at 18:05
  • thanks the thing is the old switch that I replaced had only 2 black wires connect which I proceeded to connect to the dimmer. It's installed in a metal box. I will updated the question with photos later.
    – awm
    Oct 7, 2019 at 19:12
  • Any chance the cabling system is AC cable? Oct 7, 2019 at 21:04

2 Answers 2


Connecting the switch to the black wires is safe and correct if you used the proper wire nuts. You said you made sure the connected parts were covered with electrical tape. If that's all you used, it's not good enough. Go back and use wire nuts.

Never cut off a ground wire. If you don't have a ground in the box just tuck the wire in there for the future. There is a chance you've got a ground there if metal conduit or armored cable was used and screwing in the switch would ground it but not the way it should be. The switch is safe to operate as is.

  • Thanks. I will have to go back to it. I was able to put only one wire nut. The issue I had is that the cables coming out of the box are strong thick cooper ones and did not fit in the wire nut. I might have to buy a dimmer where the wires can be held by screwes on the side as the original switch. like this one images-na.ssl-images-amazon.com/images/I/…
    – awm
    Oct 7, 2019 at 19:09
  • The yellow wire nuts should fit. Pick up a small package of them at your home store.
    – JACK
    Oct 7, 2019 at 19:21
  • thanks again, so I should just use a wire nuts without replacing the dimmer knowing that I did CUT the ground cable? what's the risk if the ground cable was supposed to be attached to the metal box as mentioned above.
    – awm
    Oct 7, 2019 at 19:49
  • I would not replace the dimmer because of the ground wire missing. If the box is grounded the switch will be grounded when screwed into it. Also, there are countless dimmers installed without grounds. Yes to the wire nut connectors...
    – JACK
    Oct 7, 2019 at 20:08
  • I actually replaced the dimmer with one that have screws to hold the wire. I still don't see if I need to do anything for grounding it and from what I was told the metal box is already grounded as it's a requirement in NYC .. attached more photos above
    – awm
    Oct 7, 2019 at 21:29

That box is grounded via cable armor, it appears

From the style of the box and the wiring coming into it, it appears that your house is wired using new-style armored cable (modern type AC, with the bonding strip), which means that the cable armor acts as the ground conductor, and thus that your box is already grounded. Furthermore, since this is a switch, you can safely ground it to the box via the yoke and screws, as per NEC 404.9(B).

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