I started the install on my new wyze thermostat and entered the wire labels that are in my current thermostat and hit next in the app and it says my system is not compatible with Wzye thermostat. Im assuming this is because I only have a furnace and no air conditioner. Does anyone know how I can proceed with the install and if I can use the thermostat?
Any help would be awsome. I only have 3 wires, W, G, RC (the RC was jumpered to the R)
The first time I set it up I forgot to mark that I have a W wire for heat, so when I got to turn on the thermostat in the end, I had an A/C-only system, so I would assume it can also be configured to be a heat-only system. I think it expects a C wire for that though and maybe the C-wire adapter can only be used when you have a Y wire as well.
You could check compatibility by indicating in the App that you have a W, G, RC and a C wire. If it then tells you it’s compatible, you should be able to use it when you get the C wire connected between the furnace and the thermostat.
If you can, I would check to see if there is an unused wire between the furnace and the thermostat that you can use for that. I had an unused blue and brown wire from end to end, so after connecting the blue wire to C on both terminals I didn’t have to use the C-wire adapter.
Thanks for the response. I do have additional wires in the wall so I will give that a try.
If there’s a blue one you can use that as C, and if there is an extra yellow one, you can use it as Y, knowing that it will never be used. I assume that that should make it 100% compatible.
Those were the exact wires I had. I hooked it up and its working fine. Thanks for the help.
Awesome! Very welcome 
So this will/does work for a 3 wire no ac system
It depends on what your 3 wires are. If you have R and W and C, then yes, the wyze will work.
If you have R and W and G, and you don’t actually need G to make your furnace fan run, then it will also work, but you will need to rewire G to C on your furnace and the wyze, and will lose the ability to switch your fan on manually.
The wyze needs 2 wires to power itself, and 1 wire for each thing you wish to control with it. So 3 wires for just heat. 4 wires for heat + fan or heat + circulator pump. 5 wires for heat+ cool+ fan… etc.
I have a heat only system using 3 wires at the control panel R, W & G. it looks like I can rewire the G to C and get heat. If I want to control Fan & Heat am I able to add C for power or should I just stick w/ heat since I hardly ever control the fan independently?
If you want to control the fan, you would need to run a new C wire to be able to control the fan independently of the heat. Otherwise, yes, you could just connect the G wire to C on both ends and it would run the wyze.
The alternative to this is to connect a plug in wall 24V transformer to power the wyze on Rc and C and then run the R wire from the furnace to Rh, the W wire to W, and the G wire to G.
Thanks for confirming. I’ll give it a try
-Much appreciated