Awesome diagrams! That was a huge help! I really wish Wyze would just explain how the thermostat works rather than trying to dumb it down and leaving us all to figure it out on our own.
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Thanks to everyone who already figured this out and shared!
If you have a 24v two wire, heat only system…
C and Rc - These connections are used to power the thermostat. A 24v AC power brick can be used for this.
Rh and W1 - These are connected to a relay inside the thermostat. This is where your existing low voltage 2 wires go.
If you have a two wire high voltage system you will need to convert it to low voltage. The Aube Technologies RC840T-120 relay and transformer combination unit can be used. There are other threads explaining how to hook that up.
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Is anyone at Wyze is reading these comments?
The Wyze app both online and on my mobile device say the Wyze thermostat is not compatible with my old Coleman oil burner. Well I have news for them.
I wonder how many sales Wyze has lost because they failed to consult a knowledgeable HVAC guy for installation instructions for real-world scenarios.
There are so many posts that I suspect that they don’t bother trying to read them. There decided lack of incorporating input from end users is why they seem to take such a beating from users in the community.
Perhaps some oil fired systems were high voltage?
I also liked the idea about Wyze just telling us how the thermostat is wired and it’s needed input voltages and let us figure out how to use them.
ok, I also have a 2 wire system with 24v going across the terminals.
it seems to me, couldn’t you just jumper the the 24v power to the C terminal and that would do it ?
i wouldn’t think there is a lot of draw across the thermostat terminals. can anyone verify or explain why that wouldn’t work ?
thanks
Speadie awesome info. Here’s one for you. Bosch greenstar boiler. Clearly not designed to run with a smart stat, or even a thermostat for that matter. They want you to use their system and rely on OSA reset, which makes sense. No C wire. Thermostat input calls for a dry contact. No apparent LV transformer in the greenstar although there clearly must be one. Two wires. I have an external 24 v transformer. As currently wired the thermostat has power, will turn on the boiler (close the Rh - W1 circuit ), But it’s quite wonky - temperature reading wanders from 50 something to 68 over several minutes and is clearly not reading room temperature. If i set the temp above 67, it never displays a temperature higher than 66 and so the boiler runs. Until i turn it off with the Wyze. Wierd, i suspect a ground reference issue or something since im not supplying power to Rh.
I’m going to install an isolation relay as you suggested Thanks! i don’t need anything but heat on-off.
But wondered if you’ve run into this with Greenstar boilers and wyze or other smart stats.
The thermostat is sending power to a load on one of the wires, and the thermostat itself needs to stay powered while doing this. if you jumper R to C without a load in between them, you have created a short circuit. if you jumper C to the output wire, then when the wyze turns on that output, it creates a short circuit.
Keep it simple and remember that the Wyze Thermostat is but a fancy switch. You need to do only two things:
- Supply power to the thermostat.
It needs a power supply to function. In some applications, it can get this from the furnace; in others, it cannot. I supplied power to mine by running two wires from a 24V doorbell transformer in my attic.
- Connect wires from furnace to thermostat.
These are just the “switch” wires to turn on and off the furnace.
That’s it. It’s that simple. There are schematics in this thread, and there are a couple of good third-party videos on YouTube, but if you keep it simple and have a dedicated power supply (possibly your doorbell transformer, or one you can buy at your local hardware or even Amazon), you’re set. If you install a new transformer, just pay attention to the 110V wiring so you won’t get a nasty surprise.
Desert gecko - that’s what I’ve done and it doesn’t work.
The thermostat is powered from an external transformer via R and C.
Rh receives potential from this (R I believe).
RH and W are connected to the boiler. But the thermostat never sees W since it has a different reference - I.e. no way for the thermostat to create a full circuit using W.
All the boiler wants is W connected directly to Rh. A simple switch as you say. The thermostat does make that happen but since it doesn’t see W it doesn’t know a circuit has been completed and gets wonky. Basically Rh is getting potential from both the thermostat/transformer and the boiler (which has some kind of transformer in it somewhere.
Hence the isolation relay. Boiler references boiler and stat references stat. Everybody happy.
The relay ($15) should arrive tomorrow. I will let the board know how it goes. Is everything happy now?
Isolation relay works. Thermostat is now reading correct room temperature and turns system on and off as expected.
Thank you Speadie for the block diagram!
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I have seen people on videos who have purchased a 24 volt ac adapter to power the unit for a 2 wire system. They say it works well. But I need to know which wire on the 24v adapter do I hook up to the C on the unit. One wire is white and the other is white with a black stripe. Which one would hook up to C on the unit???
If you mean a separate 24 volt transformer is the “adapter”, and the wires are the low voltage side of the transformer, then it doesn’t matter. One wire to the relay and one to the thermostat.
Mark Case
It doesn’t matter which wire goes to C and which wire goes to Rc. It should be an isolated 24VAC output. You will need to connect the existing 2 wires for your thermostat to Rh and W1.
Make sure to tell the wyze that your “old thermostat” has the following wires in order for it to work properly: Rc, C, Rh, W1.
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Thanks for your help!!!: this was done, as per your instructions and it’s a success! At first it didn’t work then I connected the white wire to W2 which also didn’t work but then I connected back to W1 and went through the steps again and for some reason it worked that time
Great! Took me quite awhile to get it figured out but them it was simple.
Mark Case
Has anyone had the issue of boiler not turning off? 2wire system with tranformer wired rc,c,rh,w1.
Sets up fine but doesmt stop running and heating after passing set temperature. 2wires go straight to zone valve for downstairs(area im dealing with), and other two wires go directly to transforer
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Mine took rc and c from trans. And red on w1. Works like a champ
At first, I thought mine stayed on. Then I realized that a furnace has two controls: one for the burner and one for the fan. Just as the fan won’t come on until the heat exchanger gets hot, the fan won’t shut off until the heat exchanger cools down – even if the burner shuts off. This is how a furnace works.
Aside from this, we should also consider the thermostat settings. There are settings that keep the furnace from kicking in too often. My mind’s playing keepaway with me at the moment, so I can’t say what they’re called, What they do is allow the furnace to be on even when the temp isn’t precisely the number we set; they give the thermostat a small range to work with. Ultimately, this saves wear and tear on the furnace and also saves energy, when they’re set properly.
When using the adapter, what happens if you lose power, and when it comes back on, does it automatically get back online? Or is there any physical/manual intervention that has to be done? Purchased the tstat only to find out my system is a 2 wire (red/white).
Looking at adding this to a cabin so needing ease of use if the power goes down and especially when power is restored to get back online automatically.