Thermostat Power supply

[Ken.S]

according to @speadie if u use this external 24v transformer, your a/c will not work. It’s only suitable for heat only systems. If u post pix of your current wiring at your tstat & the wire nuts, we can help u wire the C wire adapter. It’s really not too difficult.

see his explanation here:

Wyze thermostat simplified block diagrams

I made a couple of simplified block diagrams to show why running the wyze thermostat requires a C wire and why if you use an external transformer, you cannot use the Cooling aspects of the wyze. Not sure if this will help anyone, but it’s worth trying. Current needs to flow through the R and C terminals of the transformer, through a load in order for that load to get powered properly. Without a complete loop back to the transformer, you run the risk of the current finding its way back through…