Sorry if I don’t get the terminology right, but I’d like to update my laundry room/mudroom so that the lights come on when I enter the room. (I hate coming home into a dark room!) I thought the easiest thing to do was replace the wall switch. There’s a single switch in the laundry room, and there’s another switch as part of a 3 switch for that same fixture out in the garage. If I replace the single switch in the laundry room, will that do anything weird with the wiring?
You need to get a 3 way switch/dimmer kit.
Thanks for this! I guess I’m asking do I need to replace the switches on both ends of the circuit (the laundry room AND the garage), or just the laundry room?
You need to replace both unless you plan on leaving the secondary leg on all the time. The z-wave three way can be used at either end and the states will get properly updated in the ST app. If you leave a standard switch in the mix, then when that switch is off it kills the power to your z-wave switch.
You have to replace both but be aware you will need a neutral at each end. It isn’t just a straight replacement. It has been a while since I swapped mine out but I believe you can use one of the extra travelers as a neutral if needed.
There are dozens of threads discussing the effort.
Depending on how you want to do it, you can just add a micro controller to one switch. That might be more cost effective. However I personally prefer to replace the switches with Z-wave myself. If you do replace, you WILL have to replace both as 3-way Z-wave is a different animal than 3-way normal. Rather than retype a bunch of stuff, I’ll refer you to this thread:
Lots of good info there, including from pretty snazzy drawings from yours truly.