Thermostat wiring diagram, voltages?

I am trying to setup a thermostat and the video instructions are useless.
It is written for the “give a man a fish” crowd. They provide no wiring diagram or troubleshooting table, that’s all I need.

A thermostat is just a simple switch triggered by a temperature monitor. The furnace does the fan delay on its own, it just needs a run signal.

All I need to know is two things- first, what are the power requirements- voltage and current at which terminals to power the device. If I don’t get that from my furnace I will just buy a 24V AC power supply, they are $15 at Jameco.

And I need to know which terminals on the thermostat control the heater on. I don’t have AC, and I can figure out which terminals do the same on my furnace.

This information should be somewhere easily accessible, The cutiese videos are at best irritating to me, you can’t go backwards and nothing is explained.


Thermostat needs 24vac. You should already have this.

(I think wyze internally jumps the 24v for H & C if single power source)

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I dont mean to hijack this post but I’m not getting answers anywhere else - I’m not an expert by far, but looking at my wiring diagram the G terminal on my furnace has nothing to do with a fan, its a low water cut off And My Y has nothing to do with cooling either. ( I have a boiler only- No fans and no cooling) I assume my R and C are correct, but where do I attach MY G and Y on the thermostat?

show the wiring of your “old” stat

This is a new furnace, they only put a temporary stat on while waiting to this one to arrive. it simply used G and Y

Please post model number and picture of the stat no matter how simple it is

im holding the cover with the battery, Wyze in background.
its a hunter 42999b

IMG_9817 - Copy

( And I did try W and rh on the Wyze along with R and C added from the furnace )

Thanks. I put it on the bench and supplied 24.0 VAC with the correct polarity across C and Rh and it does not light up. I should have tried Rc too, maybe tomorrow. I have real work to do. Hard to imagine getting a dead unit but my existing programmable is working fine.

I’m assuming you have radiators or convection type heat. To use a Wyze with regards to this diagram the “G” wire would connect to the “R” terminal (power in) and the wire from the “W” terminal would connect to the “Y” connection completing the circuit to the furnace. The low water cut off is a safety control that should never be by-passed along with the other safety switches further down line to terminal strip. You would need a “common” wire to power the thermostat also, so one would need to be connected at some point in the wiring to the “common” side of the 24 volt transformer.

Mine wouldn’t power up until I hooked up the RC wire in addition to the RH wire even though I don’t have AC either. I originally tried with what should have been the only wires required for my system which was RH and W for heat, G for fan control, and c for 24v return, but the Wyze thermostat wouldn’t power up. Once I hooked up RC though, it worked.
It did tell me I had an error because like 3 wires I didn’t need weren’t hooked up. Probably thought I had a different type of system even though on initial setup where you click on wires on the existing thermostat I didn’t include them.

It’s working though

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In the tutorial if you had selected that you had RH the tutorial would have asked you to label it RC and hook it up to RC.

The Wyze system utilizes the cooling circuit RC and C to close the loop for power (24v).
@GarrettC I think this is the same for you.

I have a two wire heat. And I was scratching my head for hours trying to figure it out. Then I Did the tutorial for the last time and noticed that they had us label the RH as RC. Then I hooked it up this way and it turned on.

If you don’t have that hooked up this way it will not power on.

I have another issue happening but I won’t bring that up here lol.


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Ah, that makes sense. I must have made a mistake during that part. Although, since RH is typically for cool and RH is typically for heat, I wonder if that is the reason several people posted that their AC was running when the thermostat is calling for heat?

Yes I think so.

The app was said to have a swap feature in settings of the thermostat (swap cool for heat)

I’m going to try my android phone to see if it’s in those settings. It’s not in ios14.

For most air handlers that have heat and ac, you have one power source and it’s usually RC. Then the corresponding wires for heat W1 and a/c Y would trigger the respective systems. C is the common/ neutral wire of the same power source.

The Wyze thermostat uses RC and C for powering itself.


Thank You !!
I’ll try that as soon as the replacement arrives to replace the “32” display

Rc=Rh, that did it. There is no internal link, it has to be done at the thermostat.Why they don’t simply provide a wiring diagram is beyond me, and then they force me to watch sophomoric videos and paste stickers on wires grrrrr.


Excellent information. I am trying to use two of these thermostats in my RV which uses a 12dc system. If this is hi jacking please delete or move.
My plan is to power the Wyze Tstat with a stand alone 24vac transformer. From the Tstat output to three or four 24vac relays to switch on power from the 12vdc system to the Heater and A/C units. I think it’s seems fairly straight forward also a bit bulky and spendy. Hope my description is clear and concise.

I suppose someone makes a 12VDC to 24VAC converter. I would use Jameco, most of the electronics I get on Amazon are Chinese junk, utter rubbish. I can’t imagine there is much current draw so anything should work.

The Rc pin is the switch. C is return. Don’t hook up the green wire, the thermostat turns on the fan early for some reason known only to Wyze.

Can I jump the RH to the C to supply power to the unit?

I was unable to find a 12vdc to 24vac converter, thats why I opted for the stand alone 24vac transformer (120vac to 24vac) will only work when on shore power or through an inverter.
One of these:

Three of these:

C, (blue in my system) is the common. Put a VOM on it, depending on your furnace I believe power comes up on W and goes out on Rc. A thermostat is just a switch, except they need power to run the DC electronics in the logic and wifi circuits.

Green is the fan, if you connect that your fan will not be delayed when the furnace starts, most furnaces do that internally, waiting for the heat exchanger to warm up before moving air. Wyze turns the fan on early using the green wire, it is very annoying. Probably for safety/liability.