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Old 01-10-2009, 09:39 AM   #1
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3 way switch question

I have a light on my stairs that's connected to an existing 3 way switch setup - one at the top and one at the bottom. I would like to replace both of these with motion sensors.

I have seen this question posted before but the other folks all seem to know what the wires were. I do not know how it was wired and the light is in a location that I cannot access to see how it's wired.

So my question is, since there's so many different ways to wire a 3 way switch how do I know what wire each wire does? Is there some method I could use with a voltage tester to figure out which wire does what?

I have 2 black wires, a red wire, and a ground in each location.

Upstairs the red wire is connected to the bottom "common" and the two black wires are connected to the remaining two poles - but downstairs one of the black wires is connected to common and red and remaining black wire are connected to the two poles.

I also have the Leviton 3 way motion sensor switches. They have a red, black, yellow, and ground. The don't label "common" per say, but I'm guessing the yellow is common. They use the term traveler and expect that you have two.

I tried just replacing the top switch to see if I could get a single motion switch working while leaving the bottom switch "as it was". The best I could get working is with the bottom switch ON the motion sensor would turn the light on and off, but if the bottom switch was turned off, the motion sensor would not work at all.

I attempted swapping wires around but kept ending up with the same result - with eh bottom switch on, the upstairs motion sensor would work, and with the bottom switch off it was dead.

Andy ideas?


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Old 01-10-2009, 10:23 AM   #2
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You need to find instructions on installing those switches. You might need a neutral in the switch box. Guessing is not going to work for this. You have identified the common wire which is the most important.


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Old 01-10-2009, 10:38 AM   #3
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The ones I have installed need to work in pairs. You may have to find 3 way motion switches.

I found the leviton site, and they have a search.
Here it is.

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Last edited by jbfan; 01-10-2009 at 10:51 AM. Reason: extra stuff
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Old 01-10-2009, 10:40 AM   #4
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Originally Posted by cyberfreak95 View Post
......... since there's so many different ways to wire a 3 way switch how do I know what wire each wire does?.................
There is only one way to wire a 3-Way Switch. What may be confusing is that there is no standard colors for the travelers, The AC Pwr, or the wire to the Load.
Electrical Knowledge Repository - Colored Simplified 3-way Switch Schematic

Where did you find 2 motion sensors that can be used in a 3-Way?
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Last edited by PaliBob; 01-10-2009 at 11:14 AM.
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Old 01-10-2009, 10:56 AM   #5
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This is a post in a different forum that seems to describe what you're doing.

In a nutshell, these 2 switches need to be wired as 2 paralleled single poles controling one load.

Last edited by wirenut1110; 01-10-2009 at 10:59 AM. Reason: more info
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Old 01-10-2009, 12:13 PM   #6
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Any correctly wired 3 way setup can be changed over to a motion sensitive setup where motion at either location will turn on the light and both sensors have to time out (wiht no motion) to turn off the light. No additional wires need to be strung or fished. But manual switches left in place to override the motion detector will not operate in 3 way fashion any more.

Specifically, if there was no neutral (travelers form a switch loop) one of the travelers becomes the neutral and the other feeds the light (switched hot; wire to the load). Actually you must use the white wire for the neutral and change things around if needed. If there is a neutral (in line switches) one of the travelers is made hot all the time and the other traveler feeds the light.

To have both 3 way manual operation and motion sensing in the setup, you need to string another 2 wire cable between the switches so as to have two travelers and neutral and unswitched hot and switched hot altogether at both locations.

Last edited by AllanJ; 01-10-2009 at 12:31 PM.
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Old 01-10-2009, 02:21 PM   #7
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Another option is to use insteon switches. You can program one switch as a slave and the other as the master and have them work as three way switches without the need for the travelers. check out these at http:\\www.smarthome.com
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Old 01-10-2009, 05:01 PM   #8
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How to wire a 3-way switch:

The drawings are quite small, so you may need to enlarge to read them.

For your motion sensors, I believe you will need a neutral at each switch location. Is this the 3-way motion sensor switch you have?



Last edited by Ultrarunner2017; 01-10-2009 at 05:11 PM.
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