Thermostat Wiring Question

I’m looking into getting the Wyze Smart Thermostat. Going through the checker, putting in how the wires appear at my thermostat, they say it’s not compatible. Right now our HVAC setup is a gas-furnace only, but we might be putting in A/C next year.

At the thermostat:

B, O, G, Y, W, Not Used, R, Rc. Four wires and a jumper: Blue to B, Green to G, White(ish) to W, Red to R with a jumper between R and Rc.


Y, W, R, G, C. Two wires: White(ish) to W, Red to R. Blue and green wires are right there at the furnace, but are not connected. It’s weird that there are unconnected wires, right?

But if I swap B with Y (or C) in the checker, it works.

Am I out of luck, or can some re-connecting of things make this happen?

Thanks for any help!

The color of your blue green wire at your furnce is a bit faded.
normally, Green color wire is connected to fan on/off/auto.

if it is not connected, then you can use it for C wire (power to thermostat) and Y terminal for A/C (some higher end A/C has two stage Y1 and Y2).

W is for heat… with a capacitor, this is not a two stage nor it has DC motor that can control comfort mode).
it should be ok.

but if you are going to Upgrade your furnace future. get at least 6 wires thermometer wiring.

Yeah, that wire is a bit faded, but I think it’s clearer after the wire nut outside of the furnace (I have a picture of it, but I didn’t upload it to imgur because I’m lazy). In person you can see the difference.

A/C will be the only upgrade to this in the future - Wife and I just bought the house, and I’m pretty sure the furnace is brand new, just the wiring might be old.

surprise the techn fid not connect green. you use blue for C . but make sure it is tag as C. black usually for C.

I think that thermostat was connected by the people flipping the house, as they might have thought B for blue, not knowing that B is for heatpump stuff (which we very much do not have). Just a theory though…

I could, in theory, connect (at the funace) green to G for the fan and blue to C for common, leave white and red the way they are, and all would be well, right? Or would everything explode?

Welcome to the Wyze community @asibulsky!
Please check your thermostat wires in the compatibility checker:

I noticed that you have 4 wires connected to the thermostat but only 20 on your control board. Is there anywhere else the wires go?

The wires don’t go anywhere else, the blue and green wires are wrapped around the sheathing for the set of four wires, inside the furnace.

Hi. Did not want to create a separate discussion about wiring so I’ll write here.
I have a pretty old analog thermostat that looks like this:

Here is an internal part of this thermostat:

It has two wires (both are white) and it simply connects them together with the help of the mercury reservoir. The voltage between two contacts is 12 DC.
Is it possible to use Wyze thermostat as a replacement for this one?
Thank you in advance.

P.S. Forgot to say that this thermostat controls the furnace (on/off). There is no cooling, only heating.

I think the real wiring with color code is behind the thermostat unit.
you need to relevel if you take it out.

since both white,. you need to find out at your furnace control board which wire is carrying power.

look at your furnace board is more informative

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These two wires create a circuit. When physically connect them the circuit closes and the furnace starts to work. Basically what thermostat should do is to close the circuit when the temperature drops below the curtain level. The question is how to connect those two wires to the thermostat and will it be enough voltage (12VDC) to power it.

You should be able to connect them to the control board and use the Wyze thermostat. @WyzeChuan can confirm this.

Thank you for the answers.
Probably it will be impossible to connect it using only two wires like in my case. These two wires is simply the broken circuit that closes when the temperature reaches the certain low point. I saw video with explanation that with Nest E thermostat it is possible to replace my old one but it will work in a pulse mode to power the thermostat itself and I’m afraid it will be not good for the furnace.

I am trying to figure out if my system is compatible with the Wyze Thermostat.

Where I am getting off the rails is that I have a common R/RC wire.

It is an electric heat pump with 2-stage heat.

The terminal order is (left) Y1, Y2, W3, W2,G, RH, RC/R (Right ) L, C, O, E, W1, B, H.

Not sure what this Pulse power mode you refer to is ? ( but I am in UK not US)

I don’t think that will be the case unless its something your boiler ( sorry Furnace ) is responsible for

The Nest E is specifically intended to replace a 2 wire thermostat
The part (grey circle) which replaces the thermostat is battery powered - so no power is required from the system/house
Its boiler control switch is just a relay

I have Nest E installed in the UK and it replaced a very similar 2 wire thermostat
Might be worth double checking that

Looking at your wiring, yes it is compatible. Do you have the model number of the thermostat?

The thermostat is a Hunter 44860.

Thanks for checking.

And thank you all for the input.

Here’s what I’m seeing with that thermostat,
Y1 is for A/C
W3 is for Heat which can be W1 instead
G if for Fan
R is for Power
C is for Common
O is for your Reversing Valve usually energized in cooling mode
E is for Emergency Backup Heat strips.



Now I understand! I believe that I misunderstood @triadsharp when they listed the terminals, I thought that all had wires connected.

Your thermostat is compatible as @Brian mentioned!

@Brlepage it was a little confusing at first I agree, I read it the same as you. Then digging into the picture and the picture of the manual, it made sense. :grinning_face_with_smiling_eyes:


Thank you @Brian and @Briepage.

Key takeaway is that it is compatible and treat the RC/R terminal as an R terminal.

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