I'm trying to replace some older (late-1980s?) Leviton incandescent-only dimmers with new Lutron LED-compatible ones. There are three of them in a 4-gang box (the 4th switch seen in the pics is on a different circuit that controls a stairway light and was already replaced). Each dimmer switch controls a pair of recessed ceiling lights. The two switches on the outside (left and right--see pics) are single-pole and each control one pair of lights. The center is a 3-way that controls another pair of lights that are also controlled by a toggle switch on an opposite wall (also already replaced). The older Leviton single-poles have only two black wires while the 3-way has two black and one red wire (all hardwired--no screw mounts). I'm using new Lutron Skylark C-L 3-ways (with 1 black wire, 1 red, 1 red/white, 1 green) for all three (I can just cap the unneeded red/white wire provided for traveler on the new Lutrons per instructions in the packaging).

I've drawn a diagram to show the present wiring config. I'm guessing that the hot is coming from the black in Romex-2, which goes back to the lights (load) via black into Romex-1/3/4 (or, in the case of Switch 2 [Sw2], possibly via the Romex red in Romex-3?). All whites from Romex are gathered to one wire nut. For Sw-1/3 I'm thinking I can cap the unneeded red/white on the Lutrons and use either the black or red interchangeably to replace the older two-black config on the Levitons. I'm puzzled about how to wire Sw2 since it's a 3-way. Also, the bare grounds from the Romex are all pigtailed and screwed into the box. The old switches don't have ground wires, but the new switches do include a green ground. Do those have to be connected too, or can they be ignored (or gathered together and capped?) since, I assume, the circuit is presently already grounded.

I'm pretty much a noob with all of this and have tried to describe it as accurately as possible using what I hope is proper lingo from what I've garnered through research trying to understand all of this. Any and all help would be much appreciated. Many thanks in advance.

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  • Which wires are the travelers on your new dimmers, which wire is the common? – JACK Aug 29 '20 at 17:08
  • In the incl. instructions they show an old config and how to wire it in the new. It shows to mark (via a tag) the common so that it's the same in the conversion. In the diagram they show it being connected to the switch's black lead and the red/white being used as traveler (can't figure out how to add a pic here--do I go back and edit the original post?). I don't know for sure which is which in the current config. I assume that the red wire from Sw2 is the incoming hot (from Romex-2 black) and the two blacks are the common and traveler (one of which is connected to the red wire in Romex-3). – DaBears Aug 29 '20 at 17:46
  • Hello, and welcome to Home Improvement. Excellent job on writing and documenting your question; if the answer works for you, please accept it by clicking the checkbox. And, props for taking our tour before posting; few newbies do. – Daniel Griscom Aug 30 '20 at 12:32

The black wire from romex 2 is the hot wire that feeds your three switches and is the common. Remove the red wire from switch 2 from that bundle and hook up the black wire from your new switch to that bundle. Then take the two black wires from your old switch and hook them up to the red wire and the red/white wire from the new dimmer. All your new switches need to be hook up to the ground wire.

  • Thanks for your help. I want to make sure I understand exactly your instructions about the two black wires from the old switch. Do you mean to replace the two black wires coming out of the old switch (currently connected to the black and red wires coming from Romex-3) with the red and red/white (on the new switch) to those same two black and red wires coming from Romex-3? Does it matter which is to which? In other words, can the new red be to either of the red or black from Romex-3? Likewise, can the new red/white be to either of the red or black to Romex-3? Thanks again. Much appreciated. – DaBears Aug 29 '20 at 19:02
  • 1
    You got it. the black and red from romex 3 to the red and red/white from your new switch..... doesn't matter which one goes where. da bears. – JACK Aug 29 '20 at 19:16
  • @DaBears You from Chicago?? – JACK Aug 31 '20 at 19:02
  • Got 'er done, and thanks for the great answers, Jack! I also recalled reading somewhere that if the wires are connected wrong (i.e., the traveler?) that it's possible to have the light socket remain "hot" even if the lights seem to operate (on/off) properly. So I checked the socket without a bulb both on and off, and it's good. So thanks for your help! – DaBears Aug 31 '20 at 19:03
  • Originally from the greater Chicagoland area. – DaBears Aug 31 '20 at 19:03

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