Wyze Thermostat C Wire

awesome clarification! I didn’t think about the adapter basically nullifying the independence of the fan itself. ( haven’t had to use an adapter, yet)

that’s a great explanation…definitely bookmarked.

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I think what people forget is that in order to work with the widest selection possible of HVAC equipment the manufacturer of a thermostat is constrained by what’s already in people’s homes. After all they are only selling the Thermostat to you, not the HVAC system.

So for that reason the wiring requirements and methods for aftermarket thermostats are pretty well known and thoroughly constrained. The value being brought to the table is not how to hook it up, it’s adding intelligence to a “dumb” system or more flexibility to controlling it and scheduling it.

And frankly Wyze does a pretty good job of that. Their take on setting temperature is unique. And their scheduling and inclusion of remote sensors certainly brings value.

But the “nuts and bolts” of hooking a thermostat up are fairly standard. Now on my system a multi stage heat pump with an AC compressor using a reversing valve I had to set additional values in my previous Honeywell thermostats and my current Ecobee thermostat to get the system working.

Presumably Wyze also supports such programming steps.


@rbruceporter, you are correct sir! Power needs to be brought to the thermostat, either by a real C-wire or some other means. I just wanted to make sure @EyeInTheSky understood that an option was available that did not require running another wire in the wall. I do agree that the best option is a C-wire.

As you had said in another comment, there are options.


While the Wyze thermostat does use a C wire, it is not required. Telling people to fish walls to run a C wire is simply unnecessary.

The adapter does use the fan wire to substitute the C wire but it does not limit fan control. I’m am using the adapter and still can run the fan independently. I am right now as a matter of fact.


Yes in some control boards you can continue to use the fan independently, not all however.

And a C wire IS required. Either a physical wire you add or have already or a repurposed fan wire via the adapter. But no matter how you slice it a C wire IS required.

I did not EVER say that you need to fish a wire in the wall. That is indeed one way but it is not required. I reacted to someone else that was complaining there were not enough instructions on how to do that.

You are suggesting the need to add a C wire, which is not necessary.

Even your 1st response suggests adding a C wire, not necessary.

You can spin it however you want but a C wire is not required at the thermostat. Yes, the adapter is a alternative as it connects the C Terminal on the control board to the adapter. The bottom line is that you don’t need a C wire at the thermostat.

Unfortunately I believe you are mistaken

From the support documents on the thermostat.

Power source:

  • 24VAC through C terminal
  • C-wire adapter included
    • The C-wire adapter (included) enables you to power your thermostat without a C-wire.

Power consumption: <3.5VA

An actual physical C wire running from the control board to the thermostat is not necessary no. The adapter repurposes an existing physical wire already running from the control board to the thermostat. That repurposed wire is connected to guess what? The C wire terminal of the thermostat!

So indeed, a C wire is indeed required. This is not spin it is an actual electrical requirement. And again it is not unique to Wyze.

Haha, C terminal & C wire are 2 different things. yes the short 6" wire between the control board and the adapter is technically a C wire.

But when people post a question asking if a C wire is required they are asking if it’s required at the thermostat to see if their wiring is compatible with the Wyze thermostat. This is a pre install question, converting the fan wire to a C wire using the adapter is part of the install.

Wyze included the adapter so that those without a C wire can still use the Wyze Thermostat and making the install easier. Responding by suggesting that a C wire should be installed is not making the install easy.

Again, anyway you slice it a C wire is required. :slightly_smiling_face:

I made no such assumptions but I am sure some folks will. Just as likely some folks will interpret your statement as there is no need to power the thermostat :blush: at least not with a wire connected to the C terminal. Must use batteries! (Which is an option with some smart thermostats to get around the need for a C wire).

I never said there is no need for power at the thermostat.

I acknowledged the thermostat uses a C wire, but a C wire at the thermostat is not required.

You know as well as I, that people are asking if a C wire is required (at the thermostat) to see if their wiring (with no dedicated C wire) is compatible with the Wyze thermostat, and I stand by my answer, NO. I’ll be sure to clarify my response that you don’t need a C wire but Wyze includes a adapter to make it work.

Suggesting someone run a new wire because they don’t have a existing C wire is [wrong]. Why not tell people to use the adapter?

So @EyeInTheSky you don’t need to fish the wall & install a C wire or buy anything. I have the exact same wires as you, and using the adapter that Wyze included and my system is fully functional.

MOD NOTE: Post edited to conform to the Community Guidelines.

Ok, so, if I do not have a C wire present in my existing thermostat/AC system, which I do not, then I need to connect the C wire coming from the WYZE C wire adapter to the control board on my AC unit, correct? At that point, this C wire ONLY exists from the AC unit control board to the WYZE C wire adapter, correct? From there the WYZE C wire adapter basically simulates a C wire or does whatever it does to “create” a C wire to the WYZE thermostat, correct?

That’s correct, during install the guide in the app will show you.

Ok, cool! What’s the orange wire for that’s attached to the C terminal? So, it turns out that I do have a C wire on the wiring board of the AC unit, but when I trace it out, it goes up towards the top of the unit. It does not trace back to my existing thermostat. Heck, I don’t even know what the C wire is for. Can you please advise on what to do in this situation? What do I do with the C wire in this case?

The additional red wire on my C terminal I believe is going to the AC condenser, but I haven’t traced it out. It’s a 2 wire cable and the other wire is connected to Y which is for cooling. I’m no HVAC expert, I’m assuming when the thermostat calls for AC, this wire triggers the outside condenser.

On yours, if you have a wire on the C terminal, I’d just leave it connected and add the wire going to the Wyze adapter.