Hello, it’s my first post so apologies in advance if I am not providing enough detail. I have a question about wiring for the wyze thermostat. My current thermostat has two wires, a white wire connected to W and a red wire connected R, there is a jumper between R and RC. There is also a third unused green wire in the wall. The control panel for my furnace is a Honeywell Type L8124A, C L8151A (Triple Aquastat Relay). So the thermostat wires connect to two T/T terminals, and the third unused green wire does not connect to anything. The control panel looks exactly like this: https://support.ecobee.com/hc/article_attachments/360025328511/mceclip0.png
I’ve read several DIYstackexchange articles about soldering the green wire to the second lead of the transformer on the back of the control panel, however accessing the back of the control panel is going to be a massive pain.
Could I buy a 24v AC/DC adapter (Amazon.com) and connect one of the adapter wires to the unused green wire as a C wire? If so, what should I do with the second wire coming from the adapter? Do I need to connect both wires from the adapter to the thermostat? I’ve read that I should connect the adapter wires to C and RC on the thermostat, but I live in Northern New England and do not have a cooling system. So I am hoping I can just plug the adapter in the basement and connect it to the unused green wire then cap off the second adapter wire, instead of having to plug the adapter into an outlet near the thermostat and run cord along the wall.
You would need both of the C adapter wires to be connected to the wyze, or have the common come from the transformer on your aquastat. Unfortunately, there is no way for the current to make a loop through the load if both transformer wires are not connected to it,
I added an isolation relay diagram to that post, That is what you should be using for an aquastat with T T terminals. If you have 3 wires, then you could hook up an external transformer near your aquastat, send R, C, and W1 wires to the wyze, and connect a 24VAC NO isolation relay across T T with the coil wires being C and W1. This results in a working aquastat, and a working wyze, on only 3 wires.