Thermostat wiring diagram, voltages?

One of the main reasons I bought the Wyze thermostat was to use the Fan Cycle function, so I need the green hooked up. We use a wood pellet stove for the majority of our heat and being able to cycle the fan 10 minutes per hour works great to circulate and even out the heat from the wood stove in our house.

First of all, what’s wrong with reverse polish? Those were the best calculators!

Second … you’re going to label the ownership of a $50 thermostat as a “risk” … because “once the company is gone” there will be no app support? I’m sorry but not only are you being mellow dramatic about this, but you’re also investing all of this negative thought and energy into a scenario that has no guarantee of ever happening, and statistically speaking, it has almost zero chance of happening at all.

Wyze is probably the most advanced and cost-effective technology company I have ever seen in the United States. They have the engineering standards of Apple, but they sell their products at Dell prices … these guys aren’t going anywhere because they put out the best quality electronics this side of the planet at insanely low prices and their marketing is working … no … if a company like this is ever at risk of going away, it would be because they have been so successful, that a larger fish would try and buy them out at which point the new company would be obligated to support everything that Wyze put onto the market.

When was the last time you got burned by an electronics manufacturer in the United States? Maybe you’re all pent up because you blew a tube in that Fisher stereo system you still have in the den … Maybe you can’t play Exodus anymore on your Commodore 64 because they had the audacity to succumb to an emerging industry that their products couldn’t compete with … and now that $300 you spent in 1982 was just a total waste and had you known better you wouldn’t have taken on that “risk” in the first place…

Since when has consumer electronics EVER been an investment? Don’t tell me you haven’t dropped $50 on going out to dinner and a movie … were you taken advantage of then too?

Tell you what … go to Amazon and find me one smart thermostat that can do what the Wyze can do for less than $100 to $150 … then come back and tell us how much of a financial risk you took in purchasing this product.

Heck, I almost want to buy it from you just to keep you from irresponsible posting in the forums … what is it about speaking negatively about people in public that works so well for you?

There is NOTHING wrong with this thermostat … and it’s not a crime for an electronics manufacturer to keep their documentation simple … because it will work for the majority of their customers and it won’t freak them out by bombarding them with engineer speak that only confuses the majority of people. The intimidation factor of technobabble is one of the main reasons why people don’t try to better their lives in the first place with cutting edge technology like this … I think Wyze deserves some credit for the insanely thoughtful, thorough, and accurate engineering that they invested in this product (and all of their products). It looks elegant, it has functionality in the areas that make a difference … it has features that a smart thermostat should have yet sadly none of them in this price range do have …

Wyze stepped it up and raised the bar for their competitors … they are winning the battle because their products work at an amazing price and they are built like mac trucks! … their competition will get eaten alive once this catches on… mark my words! I’ve been a technology buff for over 30 years and companies like Wyze are diamonds in the rough … you really should give credit where it’s due instead of shouting that the sky is falling … cause it’s not!

Making an educated guess here, but the choice to use 24 volts AC for HVAC control - given the era of when that decision was made … which Im thinking was probably just before the transistor was invented … would have been the right choice since 24 VAC has been a common voltage for driving relays and even starting motors… it’s much more resilient to wire oxidation and when it comes to moving electricity over long distances, AC is the optimal choice by far since I2R losses are significantly lower in AC than with DC and those control wires - depending on the size of the house or the industrial building could be a substantially long run of wire … obviously with todays electronics, even a low 3 volt DC line over twisted pair would be ideal … but were still dealing with technology that started taking a foot hold back in the 40s and 50s and theres still a ton of it out there…

I’m not sure I agree with you on the whole chopping into the device to find its 5 volt pickup on the circuit board … power supplies tend to be a balance point in a circuit for overall current flow and in the elimination of transient current and voltage spikes which are normally handled in the power supply portion of the circuit. It would be much safer to use an external 24V AC source to power the unit if it cannot be powered from the existing wire … its always best practice to keep a device running as it was designed to run rather than hacking inside it and bypassing what the engineer did… thats more of a spit and duct tape approach and has a much higher risk in terms of causing damage (or fires as you pointed out). If you can learn which two pins need the 24 VAC to power … then using a simple 110 to 24 VAC wall adapter would be the safest way … assuming it cannot be powered by the means that the manufacturer is wanting it to be powered.

Also wanted to comment on what you said about a ground wire … with AC … ground is not your return … your return as I’m sure you know … is the other lead on the transformer that is providing the voltage in the first place. Alternating Current taps off of a transformer and earth ground is only used in AC circuits with appliances to keep them electrically protected so that if one of the AC wires inside the appliance should happen to get loose and touch the chassis … when the chassis is grounded to the earth then if a human touches it, there will already be a path for the electrons to travel to the earth through the chassis ground where if it were not grounded to the earth and a human touched the chassis with the busted wire in it, the electricity would seek the path of least resistance to the earth and it would find it through the person who touched the appliance … so for AC, earth ground is only used for safety, not for the circuit path.

This is not the same for DC … as we can actually use Earth ground in DC as part of a circuits path if we chose to do so … but AC current only flows back and forth from one side of a transformer to the other. In Home AC, one side of the transformer is the black and the “return line” is usually white with green being earth ground but playing no part in the path of electron flow except when something goes wrong.

Thanks for the info re RH not being used by Wyze in spite of standards that define it is related to heating circuits and RC being related to cooling circuits. I wired as depicted and it works fine.

For clarification, I have a very old furnace without a circuit board. It has a standalone transformer that connects directly to the gas valve with one lead passing through a two-wire thermostat.

Adding a 3rd wire into the mix and interconnected everything as depicted in this (revised) sketch makes this thermostat work with my arrangement.



It is possible to wire it into an RV without an adapter. I just wrote a write up on it if you want to see how I have mine setup. The one thing that I haven’t added yet is that you need to select boiler, radiator, or other, otherwise the AC fan will come on with the furnace. Check it out and let me know if it works for you too.
Wyze Thermostat in an RV | Cole Family Adventures

Thank you. I hope it continues to work for many years. My concern is two fold. First is the switching requirements of of DC over AC. Second is the current draw of different AC and Furnace units. The first may be of no concern as I appears the switching in the T-stat is solid state but that make the second concern more important. In my search for reasonably priced parts to convert to 24vac input to 12dvc output it is difficult to find relays rated for dc switching where the coil is powered by 24vac. I was going to try using one only rated for AC but just haven’t found the time. Did you happen to check the current draw of the AC and Furnace trigger wires? With a fractured fibula I find myself with some down time and will do some testing here also. Thank you again for being willing to test it out using 12vdc.

Great questions. I haven’t measured the current draw, but that actually sounds like fun so I might report back with some stats. That said the signal relays used are ac/dc relays that look appropriate for switching the DC furnace. Here is the datasheet for the relays that they use if you are interested. All that said take this as an opinion and not me saying that nothing could possibly go wrong.

Thank you. Is that data sheet for the relays on the wyze Tstat or the AC/Furnace? I didn’t see them on the tstat but only looked on one side of the circuit board. Didn’t want to break anything pulling off the dial.
That datasheet is for the relays in the wyze.

1 Like

Awesome, thanks. I just did some testing with an inexpensive Craftsman clamp on amp meter. These are my findings, your mileage may very.
Yellow 0.1 amps
Green 0,08 amps
White 0.15 amps
I have a coleman Tstat with unkown brand of roof mounted AC (only has one speed) and a propane furnace (identifying stickers and marking are either warn or missing). We only recently bought the trailer.

1 Like

When you mention *** Do not connect the Blue Wire to O/B *** what is O/B?
Sorry for my ignorance. In your link I think you say to connect the blue wire from the RV to the C terminal on the Tstat.

Wiring Color | Function | Thermostat Label
Green – Fan High –> G
Gray – Fan Low –> Not Connected
Yellow – AC Compressor –> Y1
White – Furnace –> W1
Red – 12 VDC + –> RC
Blue – 12 VCD – –> C


*** Do not connect the Blue Wire to O/B *** It will blow fuses if you do.
Your devices all share a common ground on the trailer and do not need this to be connected. The thermostat is setup for AC power and does not handle the DC ground properly.

Duh, Sorry, I now see an O/B terminal on the Tstat.

Yeah, You can learn from my mistakes on that one.

Pile of shame. :laughing:

I just installed mine and got this error message. I clicked through and ran through the test procedure in the app and everything seemed to work. Do you know if there is a way to constantly display the ambient temperature?

You can click skip. The RV system works a little differently so it is not being sensed.

Thanks to the feedback provided here, I’ve updated my article to include the new details and the screenshots for setting up the thermostat in the app. Please let me know if there is anything missing. I hope it helps everyone.

OK, had some issues last night. The first time the heater was called to run I realized the AC was running also. I updated the firmware with no luck resolving the issue. So next I deleted the tstat from the app and tried to re pair this time omitting the yellow wire from the set up process but when it went to find the device on the network it would not pair/find. Prior to this I could always access the tstat from my phone. This morning I found that the green wire goes to the AC fan not the furnace fan so anytime it calls for heat the AC fan comes on also. Remedy for now was to remove both the yellow and green wires so now only have heat. Also can only control it manually from the tstat. Still can’t get it to pair. Pic from original installation, “Yellow” wire edited.

Did you select “other” or “radiator” in the setup? I kept running into that issue as well. On a home furnace/AC system it runs fans for both systems so it thinks it needs to do that on our setup as well. Telling it to use it as a radiator lets it know that there are no fans involved. The RV furnace controls its fans on its own as soon it comes on so it doesn’t need an additional signal line.

As for re-pairing it if you press and hold the tstat button it will eventually ask you if you want to factory reset. You need to do this before it will let you pair it again. It is also under settings if you can still get to that screen on the tstat.

Think we have success. Thank you so much for all your help. One more question I don’t believe anyone answered when I asked before.

Is there a way to get the Tstat to constantly display the ambient temp?

Awesome, I glad it worked out. I haven’t found any way to have it always on. It only shows up when I walk by. You might be able to do a feature request. I think that would be a nice option so I can see it across the room.

1 Like