3-way setups in Z-wave land are a bit of a different animal than normal three way setups.
A “standard” 3 way has wire coming form the breaker box (LINE) to the first switch. Then you get two traveler wires running from the first switch to the second switch. Then from the second switch you get one wire (LOAD) running to the light fixture. Finally from the light back to the breaker box (neutral). Usually looks something like this:
Note that the color of the wires may be different. These are the colors I usually had, but there’s no certainty that yours will be the same.
Now, in a z-wave setup, regardless of whether you are doing dimming or just on/off, you need a z-wave master switch. This will be connected from from the breaker box (line) to the light (load). The regular electricity does NOT flow through the second switch in a three-way setup. Instead the second switch (call in Aux Switch in Z-wave speak) is connected to the master switch by a traveler wire and when you press the aux switch a slight bit of power flow through the line telling the master that the aux is being pressed and to do something about it.
In most situations you can use one of the traveler wires to act as the load wire. In the second switch box you’ll bypass the switch and connect this traveler directly to the load line. Then use the other traveler to tie back to the primary/master switch. Like so:
The other important thing to note here is that the AUX switch in a z-wave setup will ALWAYS require a neutral. The Master may or may not. Usually it does, but there are some (GE/Jasco 45612, for example) that do not.
Depending on where you have neutrals or don’t have neutral, sometimes it’s better to have the primary switch second and the Aux first. This can be done with the same sort of wire swapping:
So, with any three-way in z-wave land you NEED to use z-wave aux switch. Aux switches typically are the same for dimming and for non-dimming setups. They are interchangeable usually.
Sorry for the long post… but one more important thing I need to say: This is all generally speaking. There are quite often exceptions to the rules in terms of how wiring was setup or your home or how z-wave switches work. I’ve typically used GE/Jasco, Evolve, and Intermatic. Other brands may be a little different. Please follow whatever instructions come with your switches and consult an electrician if you are unsure of anything. Okay, CYA disclaimer out of the way… have fun!