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Thread: What to do With Extra Wire

  1. #1
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    Jun 2020
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    What to do With Extra Wire

    I'm trying to install a Lutron C-L Dimmer for lights switched from two locations. The existing wiring consists of Two Black Wires, Two Red Wires and the Ground Wire. I tried account for the extra black wire by connecting the two black wires and the black wire on the dimmer. While this allowed me to turn the light on and off as well as use the dimmer feature, it disabled the other switch. Can I connect the two red wires and the red wire on the dimmer? I would appreciate hearing from anyone who might have a viable solution to "What to do With Extra Wire."

  2. #2
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    Quote Originally Posted by TroutBum View Post
    I'm trying to install a Lutron C-L Dimmer for lights switched from two locations. The existing wiring consists of Two Black Wires, Two Red Wires and the Ground Wire. I tried account for the extra black wire by connecting the two black wires and the black wire on the dimmer. While this allowed me to turn the light on and off as well as use the dimmer feature, it disabled the other switch. Can I connect the two red wires and the red wire on the dimmer? I would appreciate hearing from anyone who might have a viable solution to "What to do With Extra Wire."
    What you are describing is a 4-way switch. That would mean the lights are switched from at least 3 locations. The black going to the next device would go on the brass. The reds would connect to the blue (for communication).
    LED, Incorporated
    Raleigh, NC 27614

  3. #3
    Senior Member
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    This is quite simple actually and I'm not sure if you're an electrician or not - (I'm leaning towards not), but for informational purposes you have a 4-way (or more) setup and this is how they're wired traditionally with just mechanical switches:

    You have a 3-way switch at the line end, a 3-way switch at the load end, and a 4-way or possibly many 4-ways in the middle. The colors may be different in older styles of wiring but in a more modern style which is what you appear to have, they use a 3-wire (black, red, white, and ground) called travelers between the 3-ways and 4-ways.

    For the sake of simplicity, forget about the white (neutral) and the ground...those are all tied together. In a 4-way setup, the black and red wire go from one 3-way switch to the 4-way and from the 4-way there is another black and red wire that go to the other 4-way switches (if there are multiple) until they get back to the other 3-way switch. Think of as one as incoming and the other as outgoing (although the order doesn't matter). When the one pair connects to the black screws on the 4-way and the other pair connects to the silver screws. Lutron's maestro style dimmers and switches are not dumb mechanical switches so they can accomplish the same thing with 3 screws. The blue screw is the communication screw so you have to make sure that whichever wire you connect to one blue screw is continuously connected to the blue screw. For me, I make life easier and just connect the red wire to the blue screw. I connect the red wire to the blue screw on the 3-way switches on the the 4-way setup I connect BOTH red wires to the blue screw - you can make a little pigtail if you like or put one on the screw and backstab the other though pigtailing is better. There are no "extra" wires because that red wire has to continue to the next blue screw. If you do that, everything else will work fine but follow the instructions on the little paper.

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