3 Motion switchs working together on 2 wire?

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qwerty12345

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My foreman put me on lighting in a bathroom, there are 2 doorways leading into the room and the only way to turn on the Lts is 3 ceiling mounted motion sensors. There is alot going on with this Lting circuit elsewhere but it breaks down like this: there is a feed in (12-2) and that jumps between 3 motion sensors in the ceiling, then out of the last motion sensor I pulled out a switch leg. Call me crazy, but I have a feeling I should have pulled a 3 wire, almost like smoke detc. in a house, don't they need someway to 'communicate' with each other? It is essensitally like a 3/4/3way system but only with 2 wire constant hot. Will this work or should I get the fish tape ready after the sheetrock is hung?

PS - this is my first post, I hope I followed the rules, I'm not asking how to do this task, just if it will work.
 
Your three wire feeling was probably right.Unless you have a special motion detector.

The standard motion detector has to have a hot and neutral for power to the the electronics, then you would need a third wire to return to you lights to make and break the power off the relay in the motion detector.
 
qwerty12345 said:
Will this work or should I get the fish tape ready after the sheetrock is hung?

PS - this is my first post, I hope I followed the rules, I'm not asking how to do this task, just if it will work.
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Your post is fine-- we have no rules here. :grin:

I agree that you need to get out the fish tape but why wait until the sheetrock is hung. Do it now.

Feed the first sensor then 3 wire to the next 2 sensors and then switch out to the light. Good luck.
 
I'm not doing it now because I've already expressed myself and he told me this application didn't call for 3wire so I'm just going to do it, this is the first of 7 identical bathrooms so I'd like to be sure. I was kind of hoping for a bit of an explination of how/why we would need a the 3rd wire so I would have something to back myself up with besides "I don't know dude, I've just got a feeling we should have 3-wire between them"
 
qwerty12345 said:
I'm not doing it now because I've already expressed myself and he told me this application didn't call for 3wire so I'm just going to do it, this is the first of 7 identical bathrooms so I'd like to be sure. I was kind of hoping for a bit of an explination of how/why we would need a the 3rd wire so I would have something to back myself up with besides "I don't know dude, I've just got a feeling we should have 3-wire between them"
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With a 2-wire run from supply to sensor to sensor to sensor to load, and since the neutral must reach the load, you will only be able to supply each sensor with a hot and a neutral; where's the load supposed to receive its switched power from?

Alternately, you can provide the first sensor with a hot and neutral, and the second and third sensors with a switched hot and a neutral, effectively placing the three sensors in series, requiring that they all sense motion, and in the correct order!

As long as the sensors can be parallel, and they do not require a neutral, you can do this by placing the feed and the load at the same sensor, placing them in parallel, enabling any one to independently energize the lighting.

If each sensor has line, neutral, and load terminals, and they can be paralleled, each sensor must have a hot, a neutral, and a switched leg conductor to the load. This requires three conductors between sensors.
 
danickstr said:
how would you know if the sensors can be paralleled? would they need to be self rectifying?
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You will probably have to contact the manufacturer. If they cannot be paralleled, you could always use each one to operate a relay, and connect the relay N.O. contacts in parallel. Now we're probably getting more complicated than you wanted to.
 
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