Recommended thermostat devices?

Good morning everybody,

I recently moved into a new home. I am now living in a 71qm loft. Unfortunately isolation is pretty bad… but I’ll improve that soon :stuck_out_tongue:
I got OpenHABian running on a RPi3+ and have some Philips hue and “some” Xiaomi products connected. My next planned step is to install thermostats to control heat. What devices are recommended for this? :slight_smile: Thanks in advance!

Heating is a complex, usually underestimated topic with no quick-and-simple solutions.
There’s no such recommendation, and as you can attach almost everything to openHAB, you would need to be more specific what you expect them to be. That’s why we dislike these types of simple but widely open questions.
So: how many controllable heat sources do you have and of what type are these ? Radiators or others, too ?
Other HVAC devices to affect temperature ?
Thermostats are to be just dumb valve opener devices ? To include thermometers and the ability to set a target temperature and have thermostats regulate that ? Sub-system to include advanced stuff like close-valve-if-window-opened ? What’s your programming capabilities, will you be able program your heating control loop in Xtend ? Do you have access to the boiler controller and/or pumps ?

Oh, sorry. Seems I really did underestimate this ^^,

I got radiators, 5 of em. I got temperatur sensors in my space and got also have contact sensors on my windows (not all of em right now). My programing skills should suffice to create a working system I think… I have no Idea about Xtend though and as I rented the appartment I have no access to the boiler controller and pumps. All I got are the radiators, my openHAB and the devices connected to em.

Ok so it’s a typical rent-a-flat scenario. Yes this needs to be checked first as there’s a fair amount of unbelievably naive queries just looking for some device without explaining the environment and functionality they’re after. I should have even asked more questions such as “type existing devices” and “power available at radiator locations” and more.

As you already run temperature sensors and window contacts, you’ll want to reuse those instead getting new ones. What sort of devices are these ?

I’d suggest looking at the MAX! system. Cheapest among alternatives but rather solid in mechanical terms.
There’s window contacts and display/panel units available, too.
But get a bundle with the maxcube (gateway unit) right away, too, instead of trying with a CUL RF unit as some people do (former FHEM users, usually).

You can either use the MAX! GUI (you have to use it to setup devices anyway), have the MAX! system work on its own and just display states in OH, or you can override using setpoints in OH GUI and making use of your own temperature sensor values and implement the control loop in OH rules.


Have a look at my My Central Heating Solution using Thermal Actuators thread - might give you an idea of what’s achievable :slight_smile:

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Yeah that’s another possible solution. But those actuators you show are actually meant to power floor heating.
That is what I’m using as well for my floor heating house level, and as the OP and me already have temperature sensors it’s as simple (as far as HW is concerned) as to connect these valve actuators only.

But there’s two major differences usually found between radiators and floor based heaters:

  1. you need power at the radiator locations (while floor heating actuators are usually located in some utility room)
    Sorry to tell but your picture showing that SOnOff is pretty ugly, noone will want to have that in a loft …
    and no, it’s not easy to hide that well without (re)decorating walls etc.
  2. you don’t have a handle at the radiator(s) to quickly manually override your target temperature, and no display (sure these you can add in some way or another, but in my proposed MAX! solution they’re already contained).


They are ‘standard’ Wax Thermal Actuators, originally designed in Germany by a great chap called Micheal. (What is shown in the link is a copy)

‘most’ underfloor heating manifolds valves use an M30 thread and a piston with ~4mm travel.
Which curiously is the same valve arrangement found in Thermostatic Radiator Valves.

There are M28 versions out there and Micheal’s company provide a huge range of adapter rings for other valve bodies.

I have a range of clients who have UFH manifolds for ground floor heating and TRV units on radiators on other floors. (With one client running his radiators from manifolds for reduced cabling and only tiny lockshield valves on each radiator)

All of these are controlled using identical WTA, with either 24vdc or 220vac switched power.
I also use the 4 wire variants, using the microswitch circuits to call for heat from the source, to prevent pumping into a closed system.

This also helps as the microswitches don’t close until the valve is fully open (if the valve jams, the microswitches don’t close) AND after power down, the microswitches open about 3 minutes before the valves are fully closed again, which helps with pump over run to allow for boiler cooling and prevents kettling.

Taking it a step further, I provide a boiler heat call interlock, so that valves (and pumps) can be cycled during the summer months without calling for heat, so that when the winter returns, there is less likelihood of any valves being jammed.

Obviously this is a totally wired solution, so not ideal for a retro fit or Rental tenant situation.

I do like the Max! System, but as it’s wireless, it’s not something I’d ever use. (Just my business policy)

Yep - as I said in that thread, running it like that was totally temporary and ugly, because I knew I was moving, and wanted a proof of concept so when I install in the new house, I can do it neater!

As @MDAR said, these actuators fit perfectly onto thermostatic radiator valves - M30 thread - and as @BlaXun has temperature sensors already, there’s no need for any products with their own temperature control built in :slight_smile:

Someone with a little extra time can make a solution like mine that looks much prettier - mine could have been improved greatly by running the mains cable along the wall in some mini trunking, and securing the Sonoff behind the radiator out of sight, and would have been “rental friendly” :slight_smile:

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That is EXACTLY what I did!!
Well… Almost. I was able to neatly pull out some skirting boards and run wires behind them. Not everywhere though. The rest was done with mini trunking.

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Would love if you could show some photos in my original thread! :smiley:

Well all three of you are brexiteers while the OP is German so maybe our sense for aesthetics is just a different one (:wink: ) but either way mechanics are different over here.
But yes, you can get these actuators with adapters to any sort of valve.
And yes, the OP can use that on his radiators as he doesn’t need (additional) temperature sensors. I even meant to confirm that in my post.
Still, I’d always advise not to take this route to operate radiators in a rented room (a single one, even).
My points were on
a) the need to deploy power cables (mains or 5V or whatever) which are typically not present at radiator locations in a retrofit, let alone renting scenario
b) the need to go wireless (for the same reason and BTW wireless is a fine if not to say perfect match when it’s inside a single room)
c) the common requirement to still be able to set the target temperature using a manual handle (and display, eventually).

EDIT: oh, and d) I guess you never had to convince a real German HVAC craftsmen :tm: or landlord to be allowed to apply smart tech, you lucky ones

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BTW, check out MAX! system installation and configuration walktrough .

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Oh I know that pain :frowning:
Dutch commercial landlords aren’t any different. Especially when “energy consumption cash backs” are involved.