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Thread: 3 way motion sensor switch

  1. #1
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    3 way motion sensor switch

    Hello, hoping I can get some input as I have not spec'd a 3 way motion sensor before. The lighting plan calls for a motion sensor in the garage and a 3 way switch at the top of the stairs with 3 lights (one in the garage, two on the stairs). It is wired for a regular 3 way with 14/3 wiring (includes 2 travellers). The client would like the switch at the top of the stairs to function as a regular 3 way, turn the circuit on and off, AND for the motion sensor to do the same (turning on with motion and off with the timer). Any special we need to be aware of? Thanks for your help!

  2. #2
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    I don't remember where I bought it (probably Home Depot) but I put one in at my mom's a couple of years ago, so they are available and wire in just like a 3w switch.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  3. #3
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    Raeren:

    I think you have to ask the question --- logically what is the motion detector to do?

    A couple examples:

    Is the motion sensor simply to do what it normally does? Namely to turn on a light for a time period defined in the motion detector over-riding any manual off state of the light. Having no effect on the light if manual switches had turned on the light.

    Or is the motion detector on the detection of motion to turn on the light, and turn off is done manually.

    Other combinations of logic are also possible. With a GE RR relay you could have manual control from many locations. The motion sensor could turn on the relay, and manual control could be required for turn off. Or the motion sensor could also turn off the light. Or one might add an addition timer that senses the last turn on pulse to the relay, and turns the light off after some time.

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  4. #4
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    Quote Originally Posted by gar View Post
    Is the motion sensor simply to do what it normally does? Namely to turn on a light for a time period defined in the motion detector over-riding any manual off state of the light. Having no effect on the light if manual switches had turned on the light.

    Or is the motion detector on the detection of motion to turn on the light, and turn off is done manually.
    The one I installed for Mom turns the light on with motion, and time lapse or operation of either switch will turn it off, but motion will immediately reactivate it. So, it automatically reverses the state of the light if it's off, and manually reverses it if it's on.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  5. #5
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    Seems like unless you have a system designed for components to work together with one component being a master controller of some sort, you could easily have situations where light won't turn on or off when desired.

    Only time I have used motion detection on what would in the past have been on three way switches was in a corridor in a school. Multiple motion detectors in parallel, any one of them with output "on" means the lights are on, no wall switches were installed at all, if one wanted a manual off probably would have been a single pole switch somewhere though.
    I live for today, I'm just a day behind.

  6. #6
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    Quote Originally Posted by kwired View Post
    Seems like unless you have a system designed for components to work together with one component being a master controller of some sort, you could easily have situations where light won't turn on or off when desired.

    Using active electronics you could set up a motion detector connected to two travelers at a three way or four way box which would essentially override the other switches and turn the circuit on whenever occupancy is detected. There would be no way to turn the circuit off positively from normal three ways while occupancy was detected. But you could override the occupancy detector and turn the circuit on from any of the normal three ways. Not a particularly useful configuration, and your scenario of any detector being able to close the circuit is a much more practical setup.

  7. #7
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    Quote Originally Posted by kwired View Post
    Seems like unless you have a system designed for components to work together with one component being a master controller of some sort, you could easily have situations where light won't turn on or off when desired.
    I my case, one 3w switch was replaced with the 3w motion sensor switch.

    Only time I have used motion detection on what would in the past have been on three way switches was in a corridor in a school. Multiple motion detectors in parallel, any one of them with output "on" means the lights are on, no wall switches were installed at all, if one wanted a manual off probably would have been a single pole switch somewhere though.
    That describes an 'or' gate.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  8. #8
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    For a motion sensor to operate as would a toggle switch it has to know whether current is flowing to the load (light) at the time of motion detection. You do not want the motion detector to turn off the light if it is already on. Only if the light is off at the time of motion detection should the motion detector turn on the light.

    We have to assume the motion sensor has a bistable output relay. At least while AC power exists. What happens on power loss and restoration may not be too important because one could always move and turn the light on.

    Larry relative to these aspects how does your motion detector work?

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  9. #9
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    Leviton Has companion remotes with motion sensor , or you can use a regular switch to trigger the motion switch master.

  10. #10
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    Quote Originally Posted by gar View Post
    Larry relative to these aspects how does your motion detector work?
    I haven't disassembled it, but it works as you describe. It would have no problem determining whether the light is on or off. The companion switch reverses the state in either instance.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

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