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  1. #1
    Join Date
    Apr 2012
    Posts
    203

    Question First 4-way switch install

    My garage was added onto the house around 30 or 40 years ago. I want to replace two of the light switches. There are a total of 3 switches controlling this light (the third switch is previously replaced).

    I believe that makes this a 4-way switch circuit. The first switch looks like a typical 3-way switch, so I'm guessing it's at the end of the run. It has two black wires and one white. I do NOT want to depend on their color codes though. How would I use a meter to find out which wire goes where on the new 3-way switch?

  2. #2
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    623

    Default Re: First 4-way switch install

    Quote Originally Posted by MyMilan View Post
    My garage was added onto the house around 30 or 40 years ago. I want to replace two of the light switches. There are a total of 3 switches controlling this light (the third switch is previously replaced).

    I believe that makes this a 4-way switch circuit. The first switch looks like a typical 3-way switch, so I'm guessing it's at the end of the run. It has two black wires and one white. I do NOT want to depend on their color codes though. How would I use a meter to find out which wire goes where on the new 3-way switch?
    The common on a 3W switch either goes to the power or to the light. It is often a black screw. If you set your meter to "ohms" (so that touching the leads together will show close to "zero").

    Touch one meter lead to what you think is the "commom" touch the "second" meter lead to one of the other screws. If the meter reads close to zero you have identified a possible "traveler".

    Keeping the leads in-place, flip the switch. If the reading goes to "infinity" (like nothings connected), move the "second" meter lead to the other un-known screw.

    If the meter now reads zero you have identified both the "travelers" and the common.

    "Travelers" are wires (usually black and red) that connect 3W switches. It does not matter which color lands on each switch but they must not be landed on the "common" screw.

    Any number of 4W switches can be inserted between 3W switches. Put the red & black travelers from the first 3W switch on one end of the 4W and the red & black from the other 3W switch to the other end of the 4W switch.

    A wiring diagram is usually included with each 3W or 4W switch.

    3W & 4W switches are usually wired with 3 wire romex with a ground. The wire will have a black, red and a white.

    All grounds found in a box or fixture should be tied together. They will usually be bare or green.

    The statements above will always be true but, depending on where power is applied in a circuit (in the ceiling fixture or in one end of a 3W circuit)the wiring diagrams will vary slightly.
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

  3. #3
    Join Date
    Apr 2012
    Posts
    203

    Smile Re: First 4-way switch install

    Quote Originally Posted by The Semi-Retired Electric View Post
    The common on a 3W switch either goes to the power or to the light. It is often a black screw. If you set your meter to "ohms" (so that touching the leads together will show close to "zero").

    Touch one meter lead to what you think is the "commom" touch the "second" meter lead to one of the other screws. If the meter reads close to zero you have identified a possible "traveler".

    Keeping the leads in-place, flip the switch. If the reading goes to "infinity" (like nothings connected), move the "second" meter lead to the other un-known screw.

    If the meter now reads zero you have identified both the "travelers" and the common.
    THANKS Semi-Retired Electric As I was reading your post and looking at the switch, suddenly a light bulb went on over my head (pun intended). All that's happening with either 3 way switch is that in one position the common is going to one of the travelers, and when you flip the switch the common is goes to the other. Once I figured that out the rest was easy. And all the 4 way switch is doing is toggling between each 3 way switch. In one setting one 3 way switches travelers are being used, and in the other position it uses the other 3 way switches travelers. Really simple once I figured out what the circuit was doing

    All grounds found in a box or fixture should be tied together.
    When they wired the garage they didn't run any grounds to the light switches. It would be a royal pain to run wire to them now. How important is the ground to the switches going to be, or can I leave it as is?

  4. #4
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    623

    Default Re: First 4-way switch install

    I would tie grounds together in any boxes I was working in, especially flourescent lighting circuits, since an ungrounded flourescent light may not work well, if ungrounded.

    Another important circuit is the TV and computer circuits. You could build up thousands of volts of static electricity just by walking across a nylon carpet in rubber soled shoes.

    Then,when you touch electronic equipment you will see an arc and might just have fried the appliance.

    So, you could save yourself a lot of grief by walking around with an inexpensice tester and marking the ungrounded outlets.
    Then grounding the most sensitive first, until the're all done.

    If it's just the switches the electrician knew the inspector would not find then so saved a minute or two on each switch. It's especially bad if he cut them off short!
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

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