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Thread: Adding 4-way switches to a 3-way lighting circuit

  1. #1
    DIY Member cej22's Avatar
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    Default Adding 4-way switches to a 3-way lighting circuit

    I understand that there are a myriad of ways to wire up three way switches, but that's about as far as my knowledge goes. Here's my issue. I've got three cans which are currently controlled by two 3-way switches. I want to add two more switches to control this same set of lights. Access is fairly good in that the walls are open to all but one light and one switch. What is involved in adding these 4-way switches? I'll draw up a diagram if necessary. Thanks.

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    Computer Programmer Bill Arden's Avatar
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    The 4 way switches are connected in series with the two wires that go between the 3-way switches.

    Like this
    http://gilchrist-electric.com/Images...ng-diagram.jpg
    Important note Ė I donít know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

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    Moderator & Master Plumber hj's Avatar
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    Default switches

    There is only ONE way to wire three way switches, and there are a limited, not myriad, number of ways the switches can be physically positioned. The 4-way switches are attached to the two traveler wires between the 3-way switches, AND you have to check the wiring diagram for the switches you use to determine HOW the wires attach to it, i.e. line 1/A and line 2/B.

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    DIY Member cej22's Avatar
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    Quote Originally Posted by hj View Post
    There is only ONE way to wire three way switches, and there are a limited, not myriad, number of ways the switches can be physically positioned.
    Are you playing semantics? Would you prefer I say there are "multiple configurations" rather than a "myriad of ways?"

    Here are a few different "ways," but I suspect you knew that...
    http://www.homeimprovementweb.com/in...way-switch.htm

  5. #5

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    There is only ONE way to wire three way switches
    Come on now plumber. You know he meant 3 way circuits.

    The first thing to understand is how your system is wired. You will need to take the switches out and do some simple testing. Details depend on how it's wired.

    The next thing to understand is how the 4ways work, along with the 3 ways.

    The 3 way circuit uses two traveler wires, sending power on to one or the other of them. The 4way switch simply flips the traveler connections.

    You 3way/4way system will have a 3way sw on each end and as many 4ways as you desire in between.

    Pull out the switches and see what you have in there. A diagram will be necessary, or at least an accurate written description.



    EDIT: IF you existing circuit is not wired thru the lights, all you really need is access to the three wire cable running between the switches. If you can cut that cable and splice onto it, you are good.

    Cut the cable and, in a jbox, splice on to a new 3 wire cable and run it to the first 4way, Run the 3 wire cable to the next 4 way, Run the 3 wire cable back to other end of where you cut the cable.

    The exact make up of the wiring depends on what colors the original installer used.
    Last edited by 220/221; 04-21-2009 at 05:40 PM.

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    DIY Member cej22's Avatar
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    I think this is starting to make sense. The existing circuit is not wired through the lights.

    Here's what I've got. At the top of the stairs is the first switch. 14/3 leads from there to the second switch. There isn't another set of wires in the first box. The second 3-way switch has the common wire from the 14/3 attached, and then the other screws are occupied with the hot and neutral coming from the fixtures. The red wire from the 14/3 goes into a wire nut with hot wires that come from the power source and go to the next switch on the circuit. That's the part that doesn't really match the various diagrams I have. I would have expected the red to go to the second 3-way switch.

    If I understand you correctly, it sounds like I can leave the existing three way switches in their current locations by removing the end of the 14/3 from the bottom of the stairs (it's long enough that a junction box wouldn't be necessary) and run it to my 4-ways, then eventually end back up at the 3-way at the bottom of the stairs.
    Last edited by cej22; 04-21-2009 at 06:45 PM.

  7. #7

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    The second 3-way switch has the common wire from the 14/3 attached, and then the other screws are occupied with the hot and neutral coming from the fixtures.
    You are not describing it correctly.

    1. The neutral wires are not involved in the switching.

    The red wire from the 14/3 goes into a wire nut with hot wires that come from the power source and go to the next switch on the circuit
    Here is how a 3way circuit is wired.

    The common terminal on one 3W sw is wired to a hot wire (constant 120v)

    The common terminal of the other switch is wired to the switch leg (wire going to the light)

    There are two wires that connect the other two terminals of both switches (travelers)

    It sounds like they used the red to send the power upstairs to the first switch and black and white as travelers.

    The black wire going to the fixtures is connected to the common on the bottom of the stairs.

    There shoud be two whites connected together in the upstairs box (source neutral and lights neutral.


    it sounds like I can leave the existing three way switches in their current locations by removing the end of the 14/3 from the bottom of the stairs
    Correct. pull it out and drop in to one 4way location, then the next, then back to the downstairs 3W.

    IF the upstairs switch has the RED on the common, wirenut the reds together in the 4way boxes and use the black/whites as travelers.

    When you install the 4way switches, I don't remember if they go side to side or tops/bottoms on the switch (it will have 4 terminals. Look at the diagram on the box.
    Last edited by 220/221; 04-21-2009 at 09:25 PM.

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    Plumber jimbo's Avatar
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    I always like to see a diagram in print, rather than folllow text instructions. Google will bring you such diagrams, and the little green book titled "wiring simplified" is a terrific tool for anyone doing electrical work. Available at all the hardware stores.

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    Moderator & Master Plumber hj's Avatar
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    Default semantics

    Yes. If you understand the mechanics of a 4 way switch installation, then you can project it to any "configuration", because you will realize that once you interupt the travelers between the two switches, at most you just need two wires to the four way(s), and two wires back, and you can run them anyway you wish to.

  10. #10

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    at most you just need two wires to the four way(s), and two wires back, and you can run them anyway you wish to.
    While this statement is true, it's not a good idea to deviate from standard wiring methods. The smart thing is to take the 3 wire thru the 4 ways even though you don't actually need the hot leg in switch boxes.

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    DIY Member cej22's Avatar
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    Thanks, guys. I do have the Wiring Simplified book that was recommended, but I'll sheepishly admit that I'm still trying to fully understand 3 and 4-way switches. That's probably plenty obvious.

    Sounds like I'm okay in this situation because I can add the 4-ways and hook up the new 14/3 back at the last switch exactly as it's currently configured. I'll figure it out. Thanks for the help.

  12. #12

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    I'm still trying to fully understand 3 and 4-way switches.
    It's all about understanding the mechanics of the switch. The 3W simply connects the common pole to one or the other of the other two.

    The 4way flips them. If you have blk/wht in and blk/wht out, the 4way either connects BB/WW or BW/BW

    I saw one really slick animation which showed the current flow as the switches were operated. I have no idea where it was though.

  13. #13
    Moderator & Master Plumber hj's Avatar
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    Default 4way

    Just don't do like one person wanted to do. He had installed a 3/14 w/grd from the 3 ways to the 4 way. When I told him he needed four wires to make the 4 way work he wanted to know if the bare ground would work as the fourth wire.

  14. #14
    Homeowner Thatguy's Avatar
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    3-way switches and 4-way switches act like a single SPST switch in series with a source in series with a load, but where all these things are located makes for a lot of combinations.

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    DIY Member cej22's Avatar
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    Default I'm back again

    I can't believe it has been this long since I originally posted about this. Anyway, I was able to get this originally figured out simply by cutting the 14/3 that lead from the upstairs switch to the downstairs switch. I ran it to the first 4-way location and two more subsequent 4-way locations, then back to the downstairs 3-way switch and hooked it up exactly as it was by the electricians during the original build. I'll admit that I did this because I could never really make sense of the original configuration of the 3-way switch, but everything worked just fine when I did it. I simply wired all of the like colors together at the 4-way locations and everything worked great.

    Now I'm doing the finish electrical and have run into problems installing the 4-way switches. When I installed the first 4-way switch, I wired the white wires together, and then used the black and reds on the four screws. The lights remained on whether the switch was in the on or off position. They only turned off when the rocker was held in the middle position. I moved the black and red wires top to bottom and side to side, but never got the switch working correctly. So now I'm trying to understand the 3-way switch locations to see how to correct this.

    The upstairs 3-way switch is easy. That box has just one 14/3 going into it, with the black wire being attached to the common screw. But the bottom 3-way switch box is quite confusing to me. There are four separate sets of wires in the box for this circuit. I've taken a pic so you can see what I'm dealing with. Three of the whites are wired together. Two of the blacks are wired with the red, and the other two blacks are wired to the 3-way switch. The last white is wired to the switch.

    Can anyone make sense of this in very clear terms? What is wrong?

    I'll also add that I don't think I'm completely stupid when it comes to this stuff. I added a new circuit with 12 cans on it that has both 3 and 4-way switches. That one works just fine. I just can't make sense of the old work.
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    Last edited by cej22; 09-24-2009 at 04:54 PM.

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