Should I buy those Zigbee thermostats

Hi folks,

Getting cold again, so the wife again starts asking to have some smart radiator control. She has been asking me this already for several years in a row, so should make some time for it. Have been asking already in the past questions about this in the community, but I hope that technology has grown meanwhile...

  1. I need to control quite a large number of radiators, so should be a bit affordable.
  2. Should work even in rooms where I have bad WIFI signal. So I was thinking about using a Zigbee mesh network, so I can communicate over larger distances.
  3. And it should also work when Node-RED should become unavailable for some reason.
  4. It should be as low power as possible, to avoid having to replace batteries continously.
  5. Of course it should be controllable by Node-RED.

Found these Zigbee 3.0 thermostats:


Would be nice if anybody could have a look at let me know if they fullfill all my five wishes.

Or if anybody has a better idea, then please shoot ...

Thanks a lot!!

Hello Bart :wave:
Keep in mind that battery operated devices both in Zigbee or Z-wave meshes are not repeaters within the mesh. So your plan will only work if you either already have a zigbee mesh up and running or of you plan to add mains powered devices like plugs and lightbulbs at the same time.


Ikea also has a standalone Zigbee repeater available I think. And dont forget to check the compatibility of those thermostats if you are planning on using something like zigbee2mqtt.


Hi Johannes,
Thank you very much!!!! Somebody told me that in the past, but I had completely forgotten about it...
Back to the drawing table tonight ...


What makes you think they can be controlled by Node-RED? They appear to use the Tuya app so unless the API is published (and possibly a secret key), I'm not sure how you would do that?

We have a Drayton Wiser system that also uses Zigbee TRV's though with only 3 LEDs for display. The wall controller replaces your normal heating controller and talks Wi-Fi on one side, Zigbee on the other. Batteries last anywhere from 1-2 years somewhat dependent on how far from the controller they are, a repeater would doubtless improve things for the furthest ones. They use AA batteries.

While the Wiser system does not have a published API, somebody reverse engineered it. So I can send and receive data. the API isn't that nice and takes some time to get your head around but it is OK. I query the controller for all data every minute and then use Node-RED to sort things out including creating a diff object so that I can see what changed.

I got the Wiser system because the TRV's are 1/2 the cost of the other similar systems. While they work OK most of the time, I do have to occasionally remove and completely reset the TRV and then set it up from scratch again. Not sure why, possibly the drive motor isn't quite powerful enough.

If I were doing it again, I would bite the bullet and pay for the Honeywell Evohome system instead even though the TRV's are so much more expensive.

Oh, and I should say that the Wiser and Evohome systems were my shortlist because both can operated without the cloud though both do have a cloud which is useful. Evohome does publish the API.

Oh no, I was not sure about it. That is why it was on my bucket list with 5 requirements...
Thought that perhaps all Zigbee devices where controllable by Node-RED via a gateway/hub.
So again good to new, and glad I asked it here in the forum :+1:
Since I want to do everything via Node-RED, this is not the way for me to go then.

So the Wiser TRV's are also Zigbee, but those can be controlled via Node-RED (as I can see in your tutorial).


This is very interesting information, because the batteries is what is making me doubt about whether I should go wireless or not...
Can you give some ideas of distances versus battery life?

Hmm, hard to say really. I actually don't pay a lot of attention. I try to remember to check all of the battery levels at the start of the cold season but quite often I forget and the family eventually tell me that their radiator isn't working :rofl:

Bearing in mind that the controller is on the back wall of the kitchen and the furthest TRV is 1 floor up and about 8m horizontal away through at least 1 old brick supporting wall and 1 old plaster wall plus the flooring. The old brick is harder than breeze block, very dense. The Zigbee is actually much better than the WiFi reception.

I don't think I've ever had less than at least 12m of battery life but I certainly don't really measure it.

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Don't forget to checkout the connector comptability.
Quickly checking the documentation it seems to support a number of connection types (see screenshot below).

I am just mentioning as I bought a while ago the following radiator thermostat

for which I needed to buy the following adaptor separately:

That project has been put on hold as I got problems getting a raspberry pi to reliably connect over bluetooth to the device. There were also range issues (it only seemed to work when the raspberry pi was very near the device)... and then summer came and the immediate need of the project stopped.

In the UK, you will only likely come across 2 different connectors and the Wiser TRV's come with both.

Yes, I am not a fan of bluetooth.

Yes, but Bart and I live in Belgium. The connector types in Belgium might be different from what is commonly used in the UK. I think it is good to check upfront. Anyway, I had to buy an adaptor in order to be able to connect my radiator thermostat.


Same here... For the fourth or fifth time already ...

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I personally use tado as they were the only company that worked with my quite old gas boiler directly in addition to radiator valves. Unfortunately you missed prime day because that’s when I always bought all my tado components for half price because they are quite expensive otherwise.
The tado components are very nice both from quality and a usability standpoint. There is a direct node-red integration although I use them via the openhab binding.
The big caveat here is that you are dependent on there web servers as there is no local api. It’s the only component in my home that is not 100% local but as I said above I didn’t have much choice because of my gas boiler. Keeping that in mind they had a great track record for me over the last three years where there was only one major outage for half a day over that period but even than local control will off course still work.


Very useful tip again! My god, why do these manufacturers always make it so complex...

Hi Bart, what boiler controller do you have? Does it have a standard mount like the UK ones do?

The backplate looks something like this:


If you do then either the Wiser or the Evohome controllers would fit straight on that. I fitted the Wiser one myself and it took me longer to convince myself that it really was that easy than it did to actually clip it to the existing backplate. :smiley:

Do you mean that you need to plug the controller into the backplate of your boiler. And then the controller communicates with the thermostats and controls the boiler directly? Hmm, that makes sense indeed that you have some kind of plug and play system.
Until now I was thinking of Node-RED acting as the controller that communicated with the thermostats...
I assume that the controller:

  1. Measures the temperature from the thermostat.
  2. Compares this temperature to the set point.
  3. Calculates the time the heater should remain switched on to maintain the requested temperature.

So I'm looking for a way to measure and control the temperature via Node-RED, without third-party controllers or servers...
It would be a real personal failure for me, if I'm not able to accomplish this with only Node-RED :wink:

Yes. Our boiler is slightly older and doesn't have the fine control that newer ones have, but that is also standard and if your boiler has it, the controllers will use it too. On the Wiser system, each TRV signals to the controller what % heat it wants and the controller consolidates all of the requests and, if above an internal threshold, it demands heat from the boiler. Our boiler is a gas combi but I think other types may also be supported.

No, and if you did that, you would need to be incredibly careful. Also, your insurers and the local council would probably not be happy. Really, these things need to be certified. The systems already have a lot of "smarts" built in including weather sensing. The Wiser system is actually quite basic, the Evohome is a lot smarter I believe.

You can have many stand-alone thermostats. We have only 1, in the bathroom where there is no TRV on the radiator and where we also have under-floor heating (electric so not part of the Wiser system). The thermostat also measures humidity.

Most rooms just have the smart TRV on the radiator. This senses and reports temperature of course.

The thermostat/TRV actually does that locally and, as mentioned above, reports its "demand" requirement back to the controller.

There are 2 modes on the Wiser controller. The simple mode (the only one when we started) simply measures the combined demand and controls the boiler accordingly. Works pretty well but you have to manually allow for room/building warm-up time. The other mode was introduced about a year ago I think. It uses weather information and learns the characteristics of your house so you set when you want a room to be at the chosen temperature instead of when you want to start the heating (the normal schedule) and it works out when to start the schedule.

Each room has its own schedule. Of course, you can override the schedule either by twisting the TRV to give a 30min boost/cool or via the app. Or via Node-RED and the REST API of course.

There is also an away mode that turns everything off but has a minimum temperature so that you can prevent the house from freezing if you are away in the winter. It is great to be on your way back from holiday when it is colder and to just turn on the heating from the car.

You will loose some of the ML smarts that way but certainly the Wiser and I believe the Evohome will continue to work perfectly without the remote server. If you are in the house, the app first tries to connect via the cloud and if that fails, it tries to connect locally so you can still use the app even if you block cloud access. But of course, using Node-RED, you connect direct to the controller.

You can't really do without the controller box though as it ties everything together and provides the REST API and the Zigbee interface.

As mentioned, personally, I would not want to build my own home heating controller. There is too much at stake (e.g. lives as well as the house and potentially your neighbours houses and lives). Really not worth the risk for the low cost of the controller. You would almost certainly invalidate your house contents and your building insurance as well. Indeed, in most parts of the world, it is probably illegal? Just like you have minimum certified building codes for electrics.

In my case the boiler is heating 2 circuits which both have their own pump (these pumps are not part of the boiler).
One of the pumps I can switch on/off through a relay. This relay is controlled by node-red.
If I switch it on, then boiler will sense that water temperature drops and it will start heating. The pump will pump the heated water to all open radiators in the house until node-red switch off the pump.
So I am not directly controlling my boiler but indirectly via an external pump.

Julian, very nice info!! I'm now starting to see the big picture (finally...).

This is not something I had expected...
If that is the case, I will certainly take it into account. But can you explain why there is a danger issue??

That is indeed more difficult to setup...

Is it possible to do this setup in Node-RED (because I prefer to use the Node-RED dashboard for everything) and send it to the controller via the REST API?

Mine is 17 years old and works fine, so I'm not going to replace it soon ...
I have no time yet to study it in detail, but this is from the manual:


So I have a wall-mounted thermostat on the upper floor, and one on the ground floor. These are connected to "TA". When we need heat in one of the rooms:

  • we need to turn the thermostat higher, which activates a rely to activate the pump (which is not included in the boiler).
  • we need to turn the thermostatic valves on the radiator higher in the room that needs to be heated.

I want to automate this: replace the thermostatic valves on the radiator by wireless ones. As soon as minimum 1 thermostatic valve tells Node-RED that it needs heat, then close a relay on the TA pin. So then I'm also rid of the wall mounted thermostats, since Node-RED simply opens or closes a relay to get the same effect...

I assume I have a similar mechanism compared to my fellow countryman @janvda ...

If you mess up, you could, for example, ask the boiler to continually apply heat - while the boiler should (and will) have built in safety, do you want to rely on that? The risk might be low - I'm not an expert so I couldn't say - but the impact could be very high.

Bottom line, for goodness sake take this thread with a healthy dose of scepticism all round and check with a professional first :smiley:

It absolutely is. I wouldn't say it is especially easy and I've not yet bothered but it is about this time of year and correspondingly in Spring - when weather conditions are changing - that I most think that it would be nice to have alternate schedules I could simply swap in and out. Not sure what it is like on the Evohome but on the Wiser, schedules are done via the app and it is a bit of a pain to have to go through and change every room for every day. At least you can copy 1 day's schedule to any/all of the other days but you can't copy between rooms in the app. It would be relatively easy to do in Node-RED though once you've got your head around the rather complex schema.

You will see that the connections are the same as the image I shared so it is indeed a standard boiler backplate. The difference with a smart system is that you can ignore the NOTA about the roomstat. You only have a roomstat where you don't have TRV's. We used to have our single roomstat in the hallway near the kitchen which is where the single radiator without a TRV is - you are supposed to have 1 radiator without a TRV so that there is always some outlet for heat if things go a bit awry and the roomstat is supposed to be near that rad. If ever we have to take that rad off, I'll put a TRV on it now though since we have a fancy rad in the bathroom that doesn't have room for a TRV. Actually though, with a smart controller, I don't think you actually do need such a rad anyway any more since the smart TRV's seem to fail open and the controller would fail with the boiler off.

So if you didn't want the expense of a smart heating system (though really, the main expense is the TRV's anyway, the controllers aren't that expensive). I guess you could add some smarts by replacing the roomstats with Node-RED and sensors. That wouldn't be so bad because you are keeping your other controls fairly vanilla & keeping the whole control system simple.

Just make sure that when the system fails (as it inevitably will at some point right?) it does so with the TA connection open not closed so that the boiler turns off.

There are certainly benefits to having an integrated smart heating system and I wouldn't want to go back. Having the smart TRV's on each rad is really nice and the house as a whole has a much more balanced temperature now. I know that, for some people, smart systems save money, I don't know that that is the case for us but it certainly makes the house more comfortable.

I should say that our house was built around 1900 and we are on a hill with exposure from both north and south and we are in the north of England. 2 of our outer walls are stone, the rest brick. Let's just say that it is a "challenging" and expensive environment to heat to the requirements of SWMBO :smiley: We do now have additional insulation in the breakfast room (north facing and very exposed) and the living room (also north facing with one of the long walls solid stone/rubble) which does really help.

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Good one!!

Has been noted!!!!