Thermostat Wiring Problem - Help Needed

I am trying to install the Wyze thermostat. I have hot water baseboards on a gas furnace and a separate AC system. I have attached a picture of my original thermostat wiring. I have the following wires: Rc, Rh, W (heat control), Y (AC control), G (AC fan). I added the blue C wire to my furnace transformer for the install. When I check the voltage between Rh and C, I have 24 volts. Note: Rc and Rh are on different transformers. When I wire everything as you would expect, I do not get any power to the Wyze thermostat. If I disconnect the Rc wire and plug the Rh wire in Rc spot, the Wyze thermostat powers on. But then I get wiring errors. Any ideas? Run a common wire from the AC transformer instead of the furnace? Use the C Wire Adapter? Where? On the AC or the furnace? TIA - Greg

@speadie can probably help

Rc and C need to be coming from the same transformer.
You will need to run a wire from the C side of your Rc transformer to the thermostat location in order to power the wyze. Make sure that you tell the wyze that you have both a Rc and a Rh wire during install.

Ugh, that’s a long run through a lot of walls. Can I use the C Wire Adapter on the AC unit?

What wires go directly to the AC unit? I see that your Rc wire appears to be all by itself separate from all the other wires in the thermostat run. Show a picture of the furnace wiring, the A/C wiring, and any splices of the thermostat wiring.

OK, this is going to get weird. I can’t get a pic of my AC unit right now but I will ASAP. It’s in the attic and the only access is through a small door in the ceiling of the closet. I literally have to take all the shelving out of the closet and grab a ladder to get access. But there are only 3 wires to the AC: Rc, G and Y1. I ran 18/5 to the furnace when I added the C wire so the Y1 and G are spliced into that in the basement but I was still short a wire on the 18/5 so I ran the Rc separate.

Now for the furnace. I have two zone valves, only trying to control one. First pic is the transformer in the furnace. The only connections to that transformer coming out of the furnace are the Y and G terminals on the trans. They go to the two red leads on the zone valve.

The second pic shows the external transformer. Rh goes to the 24+, C to 24 common, W1 goes to one yellow wire on the zone valve. Other yellow wire on the zone valve goes to 24 common. (Just FYI, the second red wire on 24+ goes to the zone 2 thermostat).

Hopefully that helps. Otherwise I’ll start pulling apart the closet, lol.

So, G is not hooked up at all in the heating side of things?
Then the C adapter should work. You won’t need the blue C wire - tell the wyze that you have the following wires: Rc, Rh, G, Y, W and it will walk you through wiring the C adapter.
Just ignore hooking the W wire to it, and cap off the W wire on the C adapter with a wire nut to keep it from shorting against anything. Leave the W and Rh wire where they are, you wont need to change anything on the furnace transformer.
Make sure to tell the wyze that you have a boiler/hydronic system attached to W, so it doesn’t try to run the fan on your air conditioner when the heat is on.

Correct, G is not connected to heating side. Thank you! I will give that a try this week and post an update ASAP.

It works!!! Thank you so much!! I installed the C wire adapter on the AC unit and that did the trick. Wyze really needs to update the installation app and instructions to let people know that power has to go to Rc. That would have saved me the trouble of running new 18/5 wire from the furnace. Heater type could use some explanation as well. I set it as furnace but that assumes you have a fan. Hot water baseboards must be set up as “radiator” I guess.

Of course now the firmware won’t update and Alexa added the thermostat but can’t control it but those are problems for another day.

I’ve attached a picture of the AC unit transformer just for reference in case anyone needs it.

1 Like

In most typical installs, the app does show to use Rc, but it can be easy to overlook. I think you’re setup is more unique than most I’ve seen on here.