3-way/4-way question

I am a little puzzled. I consider myself fairly knowledgeable when it comes to electrical devices. What I can’t seem to figure out is why Z-wave three and four way switches are as complicated as they are. In my home I have several four-way switch implementations and several three-way implementations. I want to replace some of these with z-wave.

Why can’t I simply replace one of the three way switches (in a box with a neutral) and leave the existing three and four way switches in the run alone? Why must I replace all the devices (which is impractical considering there is not a neutral in every box and there’s no way I’m rewiring the whole house)?

In short, I’ve got a four-way application with three switches in the house that work perfectly. Why can’t I replace one of those three way switches with a smart device that I can remotely control? Why would that affect the downstream switches? I get the fact that you need a neutral and a hot to power the z-wave switch but, in the end, it is just a switch. Why must I replace the other two?

In short, because there are multiple ways to wire a 3 or 4 ways circuit. Also you are cutting off power to one of the switch when you turn the other switch on/off. Where most z-wave switches need power at all time to operate and you need line and load at the same switch.


But, if you have hot and neutral in the box with a z-wave switch (needed to provide it power anyway), why then can’t it simply behave like any other spdt switch?

Only on a 2 ways switch you have everything at one switch box. It’s a different beast all together with 3/4 ways. You could have line hot at box 1 and load at box 2 or worst line hot at light fixture box. Link below are some standard 3 ways drawings.

That simply isn’t true. In the examples you cite, there is hot and neutral in one of the switch boxes in the first four examples as well as example 9. In these cases I see no reason why replacing the switch in the box the line enters from with a z-wave device and leaving the other switch alone would not work.

You are correct but it will be really hard for an average person to figure out the wiring and correct state of the other switches just to make it work. Nothing is impossible of course. Just not simple.

So does that mean that I can, in fact do that? In other words, is there anything inherent in the device that will preclude it assuming I have a hot and neutral in the switch box of one of the three-way switches?

As long as you can figure out the line hot, neutral and load then I don’t see any problem as long as you leave the non smart switch alone. You only need line hot, neutral and load for a smart switch to work.

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And just that quickly I realized why it won’t work. Well, it will work but it won’t be useful. The smart switch won’t know if the light is on or off without knowing the states of the other two switches. THAT is why they all need to be smart switches. Back to the drawing board!

You actually need to replace the other two with z-wave auxiliary switches, that communicate with the main z-wave switch. These 3-way and 4-way z-wave setups are conceptually the same as conventional ones, but you have to replace all of the devices for it to work right. Wired the same as before, but the main z-wave switch has to be where the first hot wire is.

The aux switches for 3-way and 4-way are much cheaper than the main, like $23.

I use Leviton dimmers, and their instructions (which you can find online) show very well how to do this. Look at DZMX1 for the main, and VP00R for remotes. They work perfectly. AS EXAMPLES

Actually, the ST cloud won’t know the state either. Those other switches won’t send any events, even though the lights’ state has changed. So yeah, if the cloud thinks the lights are on, but you turned them off downstream, then you’re stuck, and they won’t turn on from ST until it thinks they are off.

I guess it’s my fault for not making it clearer when I said “as long as you leave the non smart switch alone” I meant you can no longer be able to use them.

If you go with a Aeon Labs Micro Smart Switch (2nd Edition only for this use), you’ll only need 1 micro switch and can most likely keep all your current switches. This is the route I’ve been going for 3/4 way switched loads being added to my hub.

There are a few other posts in the community here about this and Aeon Labs has some instructions on this use on their site. Links below.

However, as others pointed out, 3/4 ways switch wiring configurations often vary in different homes. To make this work you may have to rewire some of your current 3/4 way switches OR its possible that you situation would allow you to easily wire this in. Hope this helps.



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here is how I wired up 4 way… was with previous hub almond, I am waiting for my st v2 to try it…

anyway the concepts are the same.

The key is to find the central switch. Basically there should be double traveler wires on that one. Usually it is the switch in the middle ie between the other two. This is because the electrician will have wired up a traveler or extra wire to each of the other switches on the sides… It is usually this way as this is the easiest way to wire it. You can confirm which are the traveler wires by using a multi meter and adding a temp extra piece of wire you have around and check resistence for connectivity between the traveler wires running for the central to the other switches. Anywway these are usually a different color than the normal wires… if not a different color you will have to do above to confirm (with power off obviously)

In my case my central or switch in the middle had 4 wires hooked to it not counting the ground… 2 black and 2 red.
The two reds were the traveler… This central switch will be your main (zwave) switch and the other two will be the add-on switches from GE.

All of the switches wired you will have the find the neutral… Usually a bundle of white wires in the back with a wire cap on. If it is a multi switch panel (ie more than one switch) use the correct bundle of white wires that has the wire in it from the same set of wires that the other ie blacks etc come from and goto your switch.

Once you locate your central switch wire the main not add-on switch this way… The white neutral from the bundle goes to the neutral (bottom left on the ge switch) Usually the bottom right on the original switch is the Line or hot wire. (usually a darker screw). I couldn’t tell from mine so used the bottom right… this goes to the line or bottom right on the ge switch… The other black goes to the load
(top right on ge switch)
The two traveler wires ( red in my case goto the traveler or top left (with tape on it) on the new switch. You can put one in each of the two holes

If nothing works initially the load and line wires (my two blacks) are swapped. (I had this) just swap them.
So dual travlers upper left, line lower right, load upper right, neutral lower left.

The other two switches are exactly the same and easier… Each gets one of the GE add-on switches with only 2 connections.

They original switches you are replacing should have 3 wires each not counting ground.

The red/alt color or traveler goes to the traveler on the add-on switch, the white neutral you get from the bundle wire group in the back goes to the neutral and the 2 black, or 1 blue and black that are the line and load, get wired together and you put a wire cap on them…

That is it… hope it helps.