Simple Remotely configurable thermostat for modulating Gas boiler

Hey guys,

I’ve just installed OpenHab in order to monitor my solar inverter. I really liked the platform and was looking to expand it a bit by controlling the heating at my house.

I live in the Netherlands and have a Kombi Kompakt HRE modulating boiler with an old mercury based HoneyWell thermostat in the living room. From what I understand it’s wired directly to the boiler and simply instructs the boiler to heat based on the target temperature.

Now I was looking for a simple Wifi thermostat to replace it that would allow me to simply change the set temperature using OpenHab, while also allow for manual control. I’ve been searching for a while, but I’ve been struggling to find a fitting solution.
I though my requirements to be pretty simple:

  1. Local API not connected to cloud.
  2. Able to remotely set the temperature and get the current info.
  3. Drop in replacement of my existing analog thermostat.

I’ve found some options, but none that fit this criteria:

  • Nest seems to work out of the box and fits point 3. However it’s a bit expensive and I don’t really require all it’s feature set.
  • Anna Plugwise fits 1 and 2, but seems to require a module directly connected to the boiler which just seems overkill for my setup.
  • I’ve found this Moes which seems to fit all criteria, but also seems to be a bit obscure. Couldn’t find any good documentation or reviews on it.

I would be really grateful if someone could provide some insight/recommendations/ideas on what seems to me (at least) a very simple project.

My apologies if this was already asked, I did try to search it for some days, but couldn’t find any similar topic.

Thanks in advance,

What other technologies or protocols are you running with openHAB? Does the thermostat have to be WiFi? I’m not sure any WiFi ones are strictly local-only out of the box…

Thanks for your reply. At the moment I don’t really have anything yet (except for the inverter binding which works through WiFi). This would be my first integration.
You are right of course, it doesn’t have to be WiFi. Just assumed it would be easier…

In general, a WiFi solution will be cheapest, a Zigbee solution more expensive, and Z-Wave even more expensive.

Zigbee and Z-Wave will certainly have local-only control, but you will need to use a hub or a dongle to translate either protocol to something that openHAB can understand.

There are native openHAB bindings for Zigbee and Z-Wave. There are many who use zigbee2mqtt, and then the openHAB MQTT binding.

For Zigbee, the following page lists devices that are compatible with zigbee2mqtt, and may also work with the openHAB Zigbee binding. Because zigbee2mqtt is compatible with so many devices, I tend to use this list as a defacto list of available Zigbee devices. Remember, though, that you will need something to sit in between a Zigbee thermostat and the device running openHAB, to perform the protocol translation.

I don’t know of any such list for Z-Wave. However, I actually use this Z-Wave thermostat and relay. It’s essentially a relay, and a remote (battery powered) thermostat. You pair them to each other, so they can operate in isolation of everything else fails. If you then have a Z-Wave hub/dongle you can also control the two devices via openHAB. There are other options available though.

I’m not sure how you would get away with not having something directly connected to the boiler, at least via wires. At some point, when retrofitting, a relay will probably be involved.

I’ve never looked for WiFi thermostats, but as I said before I’ll be surprised if you find one that’s available out of the box with local only control. I’ll be interested to see what others recommend!


Makes sense. Thank you for the insight and references. Still need to go thought all of it.
I was actually taking a look at that Z-Wave thermostat and relay that you recommended. It’s branded different here, but it’s the same.

I think that this Plugwise WiFi thermostat can maybe fit the bill. Seems cloudless, simple to install and with an open(ish) API. At 100 Eur the price is not bad either.

but seems to require a module directly connected to the boiler which just seems overkill for my setup

I’m not sure how you would get away with not having something directly connected to the boiler, at least via wires. At some point, when retrofitting, a relay will probably be involved.

I just meant that since the OpenTherm or OnOff wiring is already done to the thermostat, all the functionality could be implemented there, instead of, for instance, that Plugwise example that requires a wired module near the boiler that it is in turn wired to the thermostat.

Looks like if you’re in the same network it might be cloudless, but when you’re away from home does everything go through

Looks like an interesting product. Bear in mind you also have to install the included gateway.

I didn’t see anything about this, except one reference to OpenTherm - is that what you mean?

Ah, understood!

I’m still not sure. I’ve been reading the manual and other threads and although it supports remote access (so obviously some sort of remote service involved), it could just act as a sort of proxy. At this store they seem to reinforce it and also in this discussion.

Not really, but there are already 2 bindings on OpenHab that seem to work locally. The one I mentioned before and this for their older products. I think the API is not public but someone must have reverse engineer it.

I noticed and actually it triggers the system designer in me that they chose to do it this, but they must have their reasons.

They do have other products to extend the solution to a multizone one using multi wireless (ZigBee) thermostats and Thermostatic valves. I’m currently considering weather I should get this one for know (cheaper) and consider extending it in the future or just bite the bullet and get the beginning of a multi zone system.

Do you have any thoughts on the energy saving potential of multi zone systems?
Three floor ground house. Get’s a bit chilly here in the winter (-10, 0) and gas bill can be around 300 EUR in the worst month.


I’m afraid I don’t have anything useful to share on this topic! Whenever I’ve run the numbers, it’s never made financial sense to do anything smart. I look at using smart devices to improve quality of life, rather than save money. Of course, your experience may vary: if your heating is on 24/7 as standard then the gadgets may save you money quite quickly! The best way to save money in my country is to change energy supplier frequently…

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I have just swapped out all 11 of my old mercury thermostats and made my own wifi thermostats with a sonoff basic and a dht11 temperature sensor. It works really well and cost less than 20 euros each. You just need to flash tasmota onto the Sonoff and then solder the temp sensor the the spare gpio on the board. I’m not an expert at home automation but can now control each room separately at different times of the day with Alexa routines, eg I turn off all the groundfloor heating at 10pm and just have the heating working in the bedrooms, then at 6am I turn off the bedrooms and then heat downstairs, or I have a games room for my boy, he gets home from school at 3pm so the routine starts at 2 pm til 7 pm or if the front window is open you can have a rule that will turn the heating off for that room and turn back on again after 20mins when the window is closed and the heating has levelled out. Some of the rooms have a second temp sensor on the other sonoff switches that are connected to lamps, this way you can get an average room temperature reading.

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Oh, cool! I’ve also made these modules (DHT22 instead of DHT11, but otherwise the same). What cover have you got over all this?

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Really cool, thanks for sharing.
May I ask how this all integrates with heating unit (boiler??).
Are all the thermostats connected to a central boiler via the On/Off switch? Or is there any central control?

the mercury thermostats are just switches with normally 3 wires, 2 positive and 1 ground, the 2 positive wires are either switching on or off. You already have the controls switching the boiler on or off, so all you have to do is update the room thermostats.

Please make sure you turn off the electricity before messing with them.

As I mentioned before you need to flash the sonoff switches with Tasmota. This allows the switches to be controlled via Openhab using MQTT. This probably the hardest part, i’m more than happy to help. There’s lots of info on here for flashing tasmota, I use taspmota 6.5 if you scroll to the bottom of the page you fill see a file called sonoff.bin thats all you need, forget the rest.