So as I replace switches in my home to make them intelligent, I am inevitably going to encounter 3-way switches. So far I’ve been using the GE Z-Wave Smart Dimmer (In-Wall), 12724. In the case of a 3-way switch, can I just put one of these on each switch and everything will be copacetic, or do I have to do something different?
You will need one dimmer and add on switches for however many switches you have in the circuit. Your wiring will also change a bit, so take a look at what I wrote here for how to do it (if your wiring schematic matches the poster I was replying to):
This add-on / auxiliary switch should work.
How do you determine which is the master?
No. It won’t. He needs the 127xx model number one (12723 I believe).
Get out your multimeter and future out where your line is and where your load is. For a classic 3 way switch, suppose you disconnect both switches and turn on power, it should be quick to find which line has juice. That will be where the master switch goes, then wire up the add on per my other post. Keep in mind that 3 way switches can be wired a few different ways, so you may want to do a little searching to educate yourself on those.
It depends on how your house is wired. You need to determine which location has the actual hot line. Also, you need to make sure you have a neutral and not switch loops.
GE 12723 Add-On Switch is the correct add on
Sorry about that, good catch.