3-way switch quantity question

Hi all,
New to SmartThings, but not new to electrical work. Question is this…if I have a 3-way circuit with two (currently dumb) switches, when I make the circuit “smart” do I have to replace both switches with a SmartThings compatible switch or just one of them? Thanks in advance.

Welcome! :sunglasses:

This should help (this is a clickable link):

Short answer is you have to replace both. The “aux” or add-on smart switches communicate state changes to the master switch, where a standard 3-way circuit uses two separate switches to physically open or close the circuit. They are also wired differently. JD’s post above gives a lot more detail.

There are about eight different ways to wire a three-way set up in the US, and not all of them can be used with networked switches.

It is typical in the US that a three-way is wired in a sort of figure 8 pattern where flipping one toggle switch closes its loop and cuts out the other switch. That can’t be done with network switches because the radio inside the switch needs to always have power so that it can hear the next “on” command.

The method shown in your diagram will indeed work with networked master switches where the auxiliary switches are dummies connected with physical traveler wires. That’s essentially the same setup that the GE three-way set uses.

So it’s not impossible that you happen to have a switch that up that could be adapted by replacing only one of the devices. But it’s not common in the United States to have that setup.

You mentioned that the auxiliary switch in your set up is a momentary switch. Did you have that switch there before you added the fibaro? In the US, momentary switches are very unusual for lighting unless it is part of a home automation system.

A couple of more questions. Lets assume that I want to use GE/Jasco switches in this example. I get that a 3-Way circuit needs a Smart Switch and an Add-On Switch. What about a 4-Way Circuit (aka three or more switches controlling one light).

Other question: (Again assuming GE/Jasco switches) What about a single pole, single light situation (aka one switch that controls one light)? What product do I use then?

You always need a Smart Switch. For each additional 3-way, 4-way etc. you keep adding Add-On switches.


Replace every switch in an N-way setup: one master plus however many auxiliary switches you need

If you are using the GE/Jasco switches, every switch in an N-way setup needs to be specifically designed to communicate with the master, which means one master controlling the load to the light fixture and as @jhamstead mentioned, one add on switch of a matching model for each of the other switch positions.

This will be true for all of the Z wave switches in the US, and you must be sure that the auxiliary is designed to work with that particular master.

The exception: a 3 way with a micro. But not usually a 4 way

The only exception to this is if you only have a three-way set up (two switches, one light fixture) and you are using an in the wall micro at the fixture, and that micro is able two handle input switches. Many of them are. In this case, there will be physical traveler wires going from the dumb wall switch to the micro at the light.

However, as far as I know while there are some micros that can handle two wall switches in this way, Very few can handle three or more, and the wiring gets complicated.

There is one and only one model of the Aeon Labs micro that can handle a 4 way, and you do it by having two physical traveler wires from the micro, each to one dumb switch, and then having the third dumb switch wired to each of the two other dumb switches to complete the circuit.


@anon36505037 might know if there’s a similar wiring set up you could use with a Fibaro, he’s done a lot with those micros.

SPST: One master switch

For an SPST switch, you just get one master switch. If you want dimming, you get a dimming master. If you just need on/off most brands have have a slightly less expensive version of their master switch without dimming.

For the GE products, for the new zwave plus model line, the master switch is

14291: no dimming (rocker)
14292: no dimming (toggle)

14294: dimmer (rocker)
14295: dimmer (toggle)


What’s the diff between GE 14291 and 12722?

The model line that starts with 14 is the newest line. The only real difference is that it has Zwave plus instead of Zwave classic. That has two big advantages over previous generations: significantly longer range per device and much better pairing in place. Otherwise everything is pretty much the same.

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Thanks for the help. Is there a site that consistently has the best prices on Z-Wave items?

No one site, although it’s important to note that Amazon is not typically the lowest price.

Definitely check the deals section of this forum, as people post good deals there.

The GE switches are widely available, and often the best deals for those are at the big box stores, Lowes or Home Depot, when you use one of their regular coupons.

Otherwise, just shop around: