3 way with a dimmer

Discussion in 'Electrical Forum discussion & Blog' started by rockycmt, Jan 5, 2009.

  1. rockycmt

    rockycmt New Member

    Messages:
    129
    Location:
    New York
    3 way with a dimmer

    I want to wire a new 3-way circuit with a dimmer. I have done 3-way circuits before and know there are different approaches depending on where the switches are vs the fixture. Can I simply swap out the standard 3 way switch with a 3 way dimmer is any of the layouts? Are there any restrictions?

    Any oppositions to a 3-way dimmer?
  2. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    Just make sure you put the common wire in the right place.

    Generally it is the odd colored wire on the dimmer.

    Put it on either end.
  3. edlentz

    edlentz New Member

    Messages:
    70
    Location:
    Michigan
    I installed a 3 way dimmer this summer and it replaced ONE of the 3 way switches. It works fine. The other 3 way switch turns the lights off, the dimmer dims and turns off the lights as well.
  4. frenchie

    frenchie Jack of all trades

    You can also have one on each end. Double your cost & time, but well worth the convenience, IMO.
  5. jar546

    jar546 In the Trades

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    432
    Location:
    USA
    Just make sure that the dimmer is rated for the total wattage of the bulbs you will be controlling. Leave the heat sink tabs on the dimmer.
  6. rockycmt

    rockycmt New Member

    Messages:
    129
    Location:
    New York
    Jar,
    You bring up a good point I think. Or something I did not know. What consequences would I expect if the dimmer is not rated for the total watts of the fixtures?
  7. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    It will WAY more than double the cost and time.

    A standard 3way dimmer is about 15 bucks. An electronic master/slave set up is well over 50 bucks and requires a bit of rewire.

    Rarely worth the convienience IMO.

    Rocky, Dimmers get hot in normal installations. If the watts exceed the dimmer it will get really hot and burn out quickly.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    22,133
    Location:
    New England
    Depending on how far apart the switches are, it can be a real convenience to be able to dim from either end...it's up to you whether it is worth the price. Some of them are great if you need more than just two, as you can daisy chain up to 8 switches, each can turn on and off plus dim. The wiring is easier, too, but different. The hot and neutral are chained, and the third wire is the dimmer interconnect. Imagine trying to get 8 switches all working to control the lights without that technology...messy. A good electronic dimmer also saves bulbs since they perform a soft start which doesn't shock the filaments as much.
  9. jar546

    jar546 In the Trades

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    432
    Location:
    USA
    It will overheat and burn out quicker and not work properly. It would be a fire hazard.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,133
    Location:
    New England
    My guess is that a metal electrical box with a dimmer might also help act as a heat sink and help the life of a dimmer verses a plastic box.
  11. jar546

    jar546 In the Trades

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    432
    Location:
    USA
    As long as I know ahead of time, I use metal boxes where dimmers will be going.
  12. frenchie

    frenchie Jack of all trades

    Point taken on the materials, but why would it call for any rewiring?
  13. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT
    Since the heat is directed to the front, a metal box does nothing. besides, the dimmer is rated what it is. what gain would you get from using a metal box?
  14. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    The master/slave units I have seen needed power at both ends and one traveler between them. It's not complicated rewiring but it is rewiring.....(edit) if it's a retro install. If you've prewired for it, no problem.
  15. codeone

    codeone Code Enforcement

    Messages:
    160
    Location:
    North Carolina
    Metal to metal contact causes heat disipation, not that it would necessarly help in this paticular application to make a differance.
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,133
    Location:
    New England
    The metal yoke contacting with the metal box would transfer at least some heat to the metal...in a plastic box, there's not as much conduction. Effectively, I think it would make the heat sink a little bigger. Probably not enough to worry about.
  17. frenchie

    frenchie Jack of all trades

    Really? The ones I've seen basically replaced the old 3-ways; I've only had it done 3 times, but my electrician didn't rewire anything.

    I just did a little google hunt, found the installation instructions for lutron's multi-location dimmers. Look at the diagram for 3-way dim-from-either-location. Looks like a standard 3-way setup, to me...


    ...upload's not working, for some reason. I think the file's too big. Here's a link to the download page:

    http://www.lutron.com/CMS400/page.aspx?id=16977&mn=1815
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