Wired hardware components for smart radiators

Hi everyone,

I’m trying to turn a 158m² apartment into a smart home, step by step, and one of the things I would like to achieve first would be smart heating control. Currently all my radiators are equipped with simple mechanical / manually controlled thermostatic valves, so basically I start from zero, and I would be grateful for some advice about which hardware I should buy to meet my goals. What I would like to achieve is the following:

  • Temperature monitoring and recording: I would like to see the current temperature in each room on my UI (which, I guess, would be an OpenHab panel, or web interface), and also record how it changes over time. So in terms of hardware that obviously means I need a temperature sensor in every room. (Not all rooms have radiators - such as a storage room - but I still want to monitor their temperature.)
  • Setting target temperature: For those rooms which have radiators, I would like to set a target temperature. Ideally there would be two ways to do that: 1. centrally from an “all apartment UI” (could be some actual panel or a web UI) and 2. in the room itself (and then only for that room and not the others).
  • “Smart” target temperature regulation: For now it would be sufficient if I could set a time-dependent target temperature program, i.e., lower the temperature while I’m away for work, raise it when I return home, lower it further when I’m away for a longer period of a few days to weeks.
  • Failsafe mode (optional): In case my apartment loses electricity, but the overall house’s heating still works (like in case of a blown fuse in my apartment), it would be nice if the heating system would still be operable (radiator control keeps its current target temperature, target temperature can be manually adjusted at the radiator) as if it were an ordinary “dumb” mechanical / manual setup.

I guess all but the last item are easy, just the last one makes me wonder which would be the best setup, in particular because I would like everything to be fully wired, for two reasons:

  • No batteries: I have quite a few radiators, and having battery-powered devices attached to each of them would mean a lot of batteries to check and replace.
  • No wireless control: I have no wifi at home (but ethernet connectors in each room which needs to be wired up, as well of spare room in cable conduits) and no bluetooth devices either. I prefer to have wired connections only.

I don’t mind some dangling cables connected to the radiators, since there are nearby cable conduits anyway where they can just “disappear”. So far it seems that there are two standard solutions to achieve my goals:

  • Having temperature sensors in every room and electrically controlled open/close valves on every radiator, completely separate from each other (independent devices). So for each room I would get a temperature reading, and I could switch each radiator on and off by applying or not applying voltage to the valve actuator. Also each room would need an input panel if I would like to set the target temperature. The most simple way to connect them would probably to connect all devices to a common central control unit. But for the “failsafe mode” mentioned above it might be nicer to have, e.g., one Arduino or similar for each room with a backup power supply (USB power bank?), so that each room could still be operated on its own (provided the valve actuators don’t consume too much power). Without such a backup, all valves would just close (or open) until power is back / fuse is replaced, which could be unpleasant.
  • Having each radiator equipped with a thermostatic valve whose target temperature can be set both remotely and locally. That would actually be ideal for me, as far as I can see now. Basically it could work just like the “dumb” mechanical valves I have now, with the possibility to adjust them directly on the spot, but with an additional wired input channel to “turn the knob” remotely as well (and even better also with wired output channels telling me the target temperature, if somebody changes it locally, and ideally even the current temperature). Also it would be nice if they (mechanically?) kept their thermostat function if power drops. I have found quite a few devices which apparently work like this, but all of them are wireless, which means batteries + wireless control, and so they are off the table for me. (And I assume the thermostat / temperature regulation in those is also gone if batteries are empty?)

Does anyone have some suggestions or opinions on my setup? Suggestions for devices which could help me to build the latter solution, i.e., thermostatic valves with additional wired control of the target temperature (if possible still working as “dumb” mechanical thermostatic valve if power fails), would be most welcome, since I have not seen any such device (maybe there is none). But also any other advice would be highly appreciated.

Even though you may be right on this aspect, I must admit, it´s very seldom a valve is hanging (open or closed) as long as you remember to montion/exercise the valves (automaticly) once in a while.
Even if it should happen, if you monitor your temperature of the room, you could code an attention rule, if the temperature gets too high or too low. Or if you monitor the actuator, again you can code a rule to attention, if it´s open too long.
I would go for a central unit/control system. And then have the backup power added to this, insted of each individual radiator.

firstly I think 158m2 is quite small to overthinking your setup that much. How many radiators you have? why is actually a problem to have good old mechanical thermostatic heads anyway?

Issue with wired actuators is usualy these:

  • they are quite slow (full close - full open takes like 3-5minutes)
  • they are not cheap (indeed not all of them)
  • not all of them can be configured locally

I have a house with roughly 380m2 which has got 17 (i think) radiators.
When I was thinking about my heating setup, I’ve been considering changing my thermostatic heads for actuators as well, but for now I haven’t found product which would suit my needs and which would work in way I wanted. And as well costs would be too high in comparison what it can do. As well I was concerned about too often toggling my heating unit, so I do like better to have it run longer but steady than switching it on/off when some radiator think so…

So I’ve redesigned my rules and thermometers and groups to cooperate with good old mechanical valves, which are configured to comfortable temperature all the time (around 23 ish degs).

I quite understand your thinking, but really it’s not worth to do so in my opinition as your setup can efficiently work even with your current hardware. Its more about logic behind your rules, thermometers and other inputs.

You could exchange your good old mechanical valves with an electrical magnet-valve, if you think the acutators are too slow. Then it will open/close very fast. They come in all kinds of prices :slight_smile:

yes but (if technology is still the same as I know about) those makes sounds, which is something what you really don’t want at home at any time

5 radiators in 3 rooms on 2 floors.

My main reasons for making them “smart” / remote controllable / programmable:

  • I travel a lot and I would like to reduce the room temperature while I’m away, and raise it again before I return home.
  • I have a heated basement room for guests and events, which I cannot access myself (I use a wheelchair), so I want to control the temperature remotely (lower when it is unused, higher when it is used, depending on use - overnight stay or yoga class), but still allow people down there to adjust it locally with another input panel or similar.

Indeed, electromagnetic valves might be too noisy, especially in the bedroom. I’m not sure how much of a problem the switching time of wire actuators would be, as temperature probably changes slowly anyway and the target room temperature would be set ahead of using the room.

I’m not quite sure I get your point here. If I have only have manually operated thermostatic valves, what effect would rules, thermometers and other inputs have if there is no outputs, i.e., no active elements that could actually influence the heating and regulate the temperature?

I´m not sure you can get an electronic thermostat for radiators, which isn´t wireless. So I guess the only option is an actuator only… It can be a little noisy when it opens, which takes a coupple of minutes, (small clicks I assume). I´m not sure if there is any actuators which doesnt clicks.

I guess I’ll give them a try then. I actually have those in my office (and many other rooms) at work, so I can ask the building manager which type / specific model number they use. Here are hundreds of radiators, so I assume they chose an inexpensive one, and I never noticed any noise since moving into the new office 5 years ago when the building was finished. So I assume I could use those also at home.

Btw I just noticed Salus has made a new fast very low energy actuator. I´m not sure if they can fit on a raditor though. But since they are self-balanced, and opening takes aprox 30 seconds, it might be worth a try if anything else fails. They come on both 230volt as well as 24volt. They´re quite expencieve though :frowning:
Type/model is: THB23030 (230volt) and THB2430.

Salus would have wired room thermostat (230volt and 24volt) with option of programming as well.

Well radiators but no radio and no batteries AND no sound - that’s a problem. Everybody to have a retrofit scenario like you uses radio controlled thermostats so there’s essentially no (mainstream) vendor to offer wired thermostats.
You have two choices:
A) deploy wireless thermostats but omit batteries and instead “fiddle” connect them to 3.3 or 5VDC power lines (to match battery voltage). Noise usually ain’t a problem.
B) deploy dumb valves used in underfloor heating and daisy chain them to an actuator of your choice. There’s systems to run on 24VDC or 230VAC but few actuators to run on 24VDC so I’d suggest the latter. Note they’re silent but binary (open or closed only) and you need to do the programming in OH yourself then, and you will also need OH-connected temperature sensors for this to work.
These valves are available as NO (normally open) for your “out of power” scenario or as NC. In theory there’s also valves that can do 1…100% but I wouldn’t use those as they are way more expensive, less reliable and programming is much more complex. Don’t underestimate the effort to get that right.

I have deployed both in my home, using MAX! thermostats on radiators and dumb valve/actuators on underflooring.

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they are not dumb, they are quite smart, but indeed you cant change them remotely.
but… is it a problem?

Yes indeed I got your point what you wanna do, but there is no valves which do the job properly as such, you simply have to sacrifice something, either battery or sound or local adjust etc.
I’m not convincing you to not to do it, but more like giving you some thoughts because I was at similar pathway.

Setting manual valves to certain level so non of your rooms will be cold as hell or hot as hell and then set certain measuring points and rules and time schedules can do basically what those “smarts” do as well.

If you wanna have one room heated to 25 while other at same time to 13 and next day other way round it definitely won’t work, and you need smart ones…, but other than that regular setup can cover all variety of situations just fine

The Salus ones look quite nice. But I guess something simpler and cheaper would do… Apparently the size is standardized to M30*1.5mm, which is what I find for most suppliers.

I guess I would go with B, since A would still need some way to attach a wire for remote control. With B, I can probably decide whether I connect them directly to OH and do the temperature dependent switching logic in OH, or have, e.g., an Arduino per room that does the switching logic, and have OH talk to the Arduino to set / read target temperature, read current temperature, read valve status etc.

In my case yes, it is, because 1. two radiators are physically inaccessible for me and 2. the remaining radiators are inaccessible while I’m traveling. Exactly as I explained.

As far as I see, having 1. an input panel in each room to set the target temperature in that room only and 2. using the binary NC or NO valves that mstormi mentioned (and which I have in my office) would do the job for me - no batteries, no wireless control, no noise, both remote and local control.

What kind of valves are you talking about? The ones I have are simple mechanical thermostats. A knob one can turn from 0 to 5. No measuring points, rules, time schedules or any kind of electronics inside.

Some or all of this may be appropriate My Central Heating Solution using Thermal Actuators

Yes - I’m using mostly WiFi stuff, but these could be replaced with non-WiFi (or, add a WiFi network purely for IoT) options - like a Raspberry Pi with multi-channel relay board hooked up to the GPIO instead of my Sonoff 4ch devices, as just one example of how to remove a WiFi component.


if those are thermo valves they close itself when room temperature is high enough (setpoint) so water flows around (2 pipe system) and open itselfs when temperature is below setpoint, so water can flow in. There is indeed no electronic needed as this is based on physics.

Anyway, as you said you need smart electronic ones, that’s fine

Indeed, that sounds like the kind of setup I would choose (except for replacing wifi with wired components, but indeed, that should not be difficult). In fact, I have read your post before posting this topic, and it was one of my sources of inspiration for the “one room is one temperature zone with a sensor and some actuators” way of solving things.

Of course, that much I know about thermostatic valves. What I meant is that there are no “time schedules” (which you mentioned in your post) or anything like that. So no chance to change the setpoint from its constant value unless I physically access the device.

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that’s why am talking about complex system. valves itselfs are not so crucial.
if you like, take some info in post of mine

Which indeed can be way different from your situation and that’s fine

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Thanks for sharing your setup as well. Indeed, that is quite a different situation. In my case I have no access to or control over the central heating unit. This is a building with around 20 apartments and central heating, so the only point where I can control something is the radiator valves.

I just noticed that your link to the actuators seems dead… They look like EAZY Drive Series 1.1 to me - at least as far as I could figure out.

ah, I’ve missed this bit somehow… then yes, your approach is the only possible tho

It appears so - the actual item isn’t too critical, it’s an M30 threaded, NC (Normally Closed), 230v 2-wire Thermal Actuator.

Here’s an alternative which is what’s throughout my new house: https://www.amazon.de/gp/product/B01HBCW5ES/

No all of these you can buy are radio controlled and don’t have wire inputs. ZWave or proprietary 433 or 868MHz. With a radio gateway or Zwave stick you can remote configure and override target temp from OH.
On B you can do OH on top of Arduino but doing so is over the top. Keep it simple.