I posted this as a reply to a reply in another thread and realized I probably should make this a separate thread.
My present furnace / thermostat / transformer arrangement consists two wires: Rh and W. Since this apparently isn’t supported, I assume I need to install a 3rd wire and re-configure the wiring as follows. Can someone validate this approach for me, or correct it if I am wrong?
I haven’t tried this myself but I would think you would use the 2 leads from the 24v transformer to connect to the Wyze thermostat Rc and C just to power the thermostat, then use only W1 from your furnace, but I’m 100% sure.
I think you’re right about connecting to Rc instead of Rh like I’ve diagramed. I think they don’t use Rh (which is supposed to be 24VAC for the heating circuit) at all, and just want you to connect to Rc (usually for the cooling circuit.)
I think using Wi to the furnace is right, but that’s only 50% of the circuit, which is why I think COM from the xformer must be connected to both the furnace and C on the thermostat. WIll be giving this a go tomorrow, after I run a third wire.
I can say though that by connected the white wire to C and the red to Rc, the thermostat powers up.
I don’t know if mine is technically correct, but it works. I originally had a two wire system as you do RH and W that were in powered and went to an old mercury thermostat. A few years ago I added the wires C for power, G (for fan) and R for power so I could use a dumb programmable thermostat. That worked fine.
Anyway, now with the newly installed Wyze thermostat I connected RH to RH, C to C, W to W1, G to G and R to RC. I did get an error during setup about missing wires that I don’t need, but I somehow skipped it and it all works fine.
The reason I connected my RH to RH is because it contains no power.
I’m not a HVAC tech so I’m not sure, but my theory is that if you wire a external 24v transformer (separate from the furnace) directly to the Wyze thermostat then connect the W from the furnace to the thermostat, when the Wyze thermostat calls for heat it will send the 24v down the W wire and the control board should fire up. I’m just not sure if the control board requires a 24v completed circuit from the R on the board to the W. It may be satisfied just seeing 24v on W.
are you using the transformer in the furnace?
Currently your thermostat is an automatic switch that closes a between RH and W1 to turn on the heat.
RH is 24vac
For wyze power you also need a common (from the same 24v souce).
If you can add a wire from the thermostat to the furnace. That would be ideal.
If you use an external transformer:
you would connect 24v on “RC” and “C”
You would put your existing heating wires on “RH” and “W1”
If you use the furnace transformer:
you would connect your existing “RH” to “RC” and common from furnace to “C”
You would put your existing heating wire “W1” on “W1”
I finally got mine to work, I had a two wire system. I bought a 24vac transformer to add a c-wire.
from the furnace my white went to w1, my red went to g, then from the transformer one went to c then the other to Rc. Seems to be working good now.
