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There is a stairwell in our house, which is currently lit by a fixture controlled by three switches: a 4-way and two 3-ways. The wiring was done very recently and, I'm certain, in accordance to modern code (which may help you figure out the diagram, even if I don't know it).

I started with replacing the existing 4-way with a 3-way sensing switch from Lutron (MS-OPS5M). Predictably, one of the remaining mechanical switches stopped having any effect whatsoever. I was hoping, the second of the remaining mechanical switches will remain in control to allow explicit control of the light. This proved to be incorrect - sometimes it has an effect, some times it does not, and some times it disables the sensing switch (it clicks, but the light stays off).

While the new sensor works perfectly well detecting humans on the same floor, if a person descends the stairs from the upper floor, the light does not go on until one descends to the middle of the stairs - when the feet come to about the same level, where the sensor is.

So, it seems, I need either:

  • One occupancy sensor with a sensor looking up as well as sideways. This would, probably, be the easiest and most sensible option. It will let me remove the remaining mechanical switch.

or

  • Two occupancy sensors, that can work together - adding the second to where I currently have the semi-functional mechanical switch. This would provide the most complete sensor-coverage.

or

  • Figure out, what's wrong with the current setup - why is the existing mechanical switch misbehaving? I'm sure, I miswired something... Should I replace it with a 1-pole switch now, that I only have 2 switches on the circuit?

Update:

So I tried to follow Lutron's diagram linked to by mac and found it easy to connect the sole red wire on the 3-way mechanical switch to one of the black wires.

Unfortunately, that did not improve the situation much. Depending on the position of the (newly rewired) mechanical switch, the sensor either works or it does not.

I'm certain, I mis-wired the sensor when replacing the old 4-way switch with it. Could somebody set me straight, please?

In addition to ground, there were four wires connected to the 4-way switch (duh!): two red on one side, and two black on the other. The new switch has 3 connectors: one blue and two black. What do I connect to what?

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The last I looked at this issue, there's no way to do as you describe without some additional control wiring or a wireless communication network. –  mac Nov 19 '12 at 19:49
    
Why, then, would Lutron (and numerous others) be selling 3-way variants of their sensing switches? What is meant by the manufacturers as the second switch on such a circuit? –  Mikhail T. Nov 19 '12 at 20:43
    
What I saw then (and saw again now in the installation manual for the Lutron Maestro 3-way occupancy sensor switch) is that the other switch remains a traditional 3-way switch, not a second motion sensor. This manual shows you how to reconfigure the remaining 3-way switch to work with the 3-way occupancy sensor. you need to reconfigure some of the wires at the switch. –  mac Nov 19 '12 at 21:19
5  
You can't correctly replace a 4-way switch with that device. –  Brad Gilbert Nov 20 '12 at 6:43
1  
What are you doing with the unused traveler wire? Which wire are you using as your hot? What functionality do you want when the former 3 way switch (but now a simple switch with an unused traveler) is off? As others have mentioned, there's no correct way to do this, you're using the wrong product for the job, and anyone that follows after you will be rightfully confused by the damage you've done to the wiring. –  BMitch Nov 20 '12 at 12:02

3 Answers 3

I was only able to get it to work with two companion switches. The Lutron series does not work properly with two occupancy sensors. My goal was to get the apt on top and the entry way to have the lights turn on when the tenant or person entering opens the door.

I like the lutron; works really well and turns on only when needed if its truly dark.

This is how its the four way with companions would be wired

4 way switch wiring

See the diagram and the description for 4-way.
http://www.lutron.com/TechnicalDocumentLibrary/048435.pdf

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-1 Link only answers become useless when the link goes bad and are frequently confused with spam. Be sure to provide context around the link and quote relevant content in case the link goes bad. See how to answer for more details. –  BMitch Dec 6 '13 at 12:09

You cannot replace a 4-way switch with the sensor you have. The sensor you are using can either function as a 2-way or 3-way switch, it does not function as a 4-way switch.

This is what a typical 4-way circuit looks like.

4-way Switch Circuit

Notice there are two 3-way switches (on the ends), and a single 4-way switch (in the middle).
You're trying to replace the 4-way switch, with a 3-way switch. Which as you've found, does not work. Your only option is to replace one, or both of the 3-way switches with occupancy sensors.

If you no longer require all the switches, you can defiantly remove one (or all of them) from the circuit. You'll just have to splice the wires together properly in the removed device box, and cover the box with a black cover plate.

Remove a 3-way switch

You can remove either of the 3-way switches, but then you'll have to swap out the 4-way switch with a 3-way switch.

4-way Switch Circuit with one 3-way removed

Remove the 4-way switch

Removing the 4-way switch is even easier, all you have to do is splice the wires together.

4-way Switch Circuit with 4-way switch removed

This blog post might help you understand how switches work.

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You could use some Insteon (or similar) home automation devices to have two motion sensors control the lights.

You'd need two wireless motion sensors and one dual-band switch. The switch receives the wireless signal from the motion sensors and activates the lights.

You'd then deactivate the other two existing switches (or add them back as "smart" switches, see below).

When one of the motion sensors detects motion, it sends an "on" command to the switch. The motion sensor then starts an internal timer and if it does not see motion again before the timer expires, it sends an "off" command to the switch.

The only issue with this is that as you add additional motion sensors, you have a race condition to turn the lights off. This is likely not a problem for most scenarios, but if you have a super-long hallway or a giant warehouse that you're trying to cover with multiple occupancy sensors it'd be an issue.

Hypothetically, lets say you have an infinitely long hallway with doors every 15 feet. Over each door is a motion sensor, they all control the lights, and they're all programmed to time-out at 1 minute.

Someone enters from one end of the hallway triggering sensor "A", which sends an "on" command and starts its internal countdown. As they walk down the infinitely long hallway, they trigger a new sensor every 15 feet or so, each sending its own "on" command. As soon as sensor A's one minute timer goes off, sensor "A" sends an "off" command, and the lights go out.

This is where a more sophisticated commercial light control network is needed. But if you've just got three doors into a three-floor stairway, the two wireless motion sensors should work fine. If you expected people to linger in the hallway, you may have an issue, though you could just increase the time-out time to try to get around it.

You could also add additional Insteon light switches if desired to replace the existing switches--though the motion sensors would still try to turn the lights off on you!

NOTE: I've used Insteon products, but am not affiliated with Insteon or Smarthome in any way.

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