Radiator Valves

I’m looking for options for radiator valve control. I’m fairly open as long as it’s control over the radiator valve and not some other smart home system.

I was told that OH supports ZWave and thus ZWave Danfoss (and others) valves. However when I went to look at these valves the ones I found were thermostatic valves which accept a “setpoint” temperature remotely and then themselves try to maintain that temperature. That’s not what I want. I don’t care what temperature it is beside the radiator, that’s pretty useless to know or for that matter to operate it’s valve from.

I assume I could set the setpoint to MAX when I want it on and MIN when I want it off.

I’m not completely against using 240V electrical actuators and running power to the radiators I want to control. In fact I kind of like the robust simplicity and no batteries to worry about.

So what are my options?

Get separate valve and temp sensor. All products to combine these will work the way you say you don’t want them to. You can get valves meant for underfloor heating and mount them on your radiators.

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You can keep your set temp at max and turn it off completely when some other sensor tells you that you’ve reached desired temperature… i use multiple sensors, and temperature that valve reads is only one of the temperatures for that room… it’s not the one triggering the device off…

I’d suggest the 4 wire 24v versions, with microwitches to confirm the valve is fully open, which in turn could signal the Heat Call of your boiler / heat source.

Then your choice of relay array to operate them.

Obviously, I’d suggest Velbus relays and Thermostats.

But I’d also suggest Robot Electronics IP relays.

See here:


Thanks, these look grand. One worry I had was a lot of these valves are £50-60 which would be too much to get one and find out it won’t work for me, but the ones you link are cheap enough to have a hit or miss once.

I’m not sure I need the 4 wire and I note they only come in normally closed. Part of me thinks I need normally open. This is based on a design choice I made which is to keep my home automation ‘transparent’ to manual intervention. If I switch off the automation I can still use the heating as it was originally intended. Not sure how far I will get with this before something prevents it, but it currently still works. Although thinking about it, unless I find valves which have a manual, mechanical override I would still need to power the relay (not difficult) to turn a radiator off.

Much like the thread linked by @vzorglub above I will most likely be using SOnOff relays with custom firmware, so I do still have the manual button to open/close the radiator. I suppose it just comes down to whether the valves will spend their time mostly open or mostly closed. I could mix and match. The bedroom will very likely spend most of it’s time closed, but the living room will probably spend most of it’s time open. The hallway I might just leave manual and open as “base heat”.

I also don’t believe I need the 4 wire for feedback because my heating system has a locked open radiator in the bathroom, so even if all actuators are off and it takes 3 minutes to open one, the heating will not be upset if I command it on before the valve opens. Also I don’t think I will actuate all of my valves, I’m going start by actuating the ones that cause me bother, in that rooms get too warm because I’m trying to heat one other room with the whole heating, but if I shut the radiator off manually that room gets too cold, triggers heating, but the heating can’t heat it. Stuff like that which I’m currently facing.

How sure are we that these will be a simple swap for a “normal” thermostatic valve? I am about to have my heating converted from oil to gas and the company doing the job is intending on putting in thermostatic valves, which I hate by the way, but I either let them put them in and swap them (they quoted something like £14 per valve) or I ask them to not put the actuator heads on the rads I want to automate.


I rarely pay more than £15 each for them.
For example, this 24v 2 wire version

As for fitting them, the emmeti ones have an M30 thread, which is common for ‘most’ TRV bodies.

Just watch out that your plumber doesn’t use Drayton TRVs, as they tend to be M28.

You can get M28 actuators, they’ve just a little more expensive

I think it was because I was seeing the smart valves with thermostat etc. ZWave and others.

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One solid bit of advice that was given out on here some time ago was…

“Let openHAB2 control a thermostat, rather than being the thermostat”

On a slightly sore point (for this forum) I probably won’t be using OpenHab for heating control. As a professional software engineer I already invested more than a few hours in my own system which I hope to keep, but I still find OpenHAB interesting and the community is superb.

My present system can currently raise demands for independent rooms but filters those demands as it only switch the boiler on/off. For rad valve control I’ll still keep that setup, but allow the independent room demands to carry on to control the radiator valves. Need some logic in there to “relax” the valves when possible so they aren’t kept powered when there is no need.

What I mean is, if a radiator with a normally open valve has been shut as to not heat that room while the heating is running, when the heating is shut off, that valve can be allowed to power down and open. Then again it might be sensible to assume these valves are designed to be powered up for long periods of time and probably don’t consume much.

Let them fit the trvs. The actuators are then a straight swap. If one fails you can always put the trv back on temporarily.


So excuse me for thinking out loud or brain dumping here and keeping things abstract, so this could be implemented in OpenHAB or not in my case.

The “system” based on data, times or day and other conditions raises the following demands:

HEATING livingRoom
HEATING office

So logic says,

if demands with type HEATING length > 0
   command heating ON  for five minutes [1]

for each radiator actuator
   if actuator zone is in heating demands
       command actuator open for 5 minutes

Does anyone see a problem with using the rad valves this way? Demanding things on for a period of 5 minutes, btw, means nothing actually has to be switched “off”, it will naturally time out if not refreshed. It also means the valves can’t be toggled on/off/of/off repeatedly and provides natural hysteresis.

[1] - I have planned logic for later which will detect if only the living room is requesting heating and in that case and only that case the system will command (via IR sender) the electric wall heater/fire to come on. If more than one room demands heating the main boiler will be used

You need to be aware that these actuators take 3 and 5 minutes to fully open.
You can get normally closed ones, they are usually £1-£2 more expensive than the normally open ones.
They operate with a kind of wax inside that expands with heat generated from a resistance inside, the wax takes time to expand, hence the delay. They use about 5W when in operation.

That’s good to know. With my heating what usually happens is the demand, once raised, will sometimes fluctuate on and off a few cycles as the temperature bounces around the trigger, but as the first 5 minutes hasn’t expired before it triggers again the actual heating just stays on. Usually by the time the heating begins to have an effect the demand is constantly being raised. The same can happen with the demand dropping off at the temp rises.

So I would expect the same to happen with the rad valves, in that they will probably stay on for longer than 5 minutes, although… I do see “pulsing” of the heating which means it does only run for 5 minutes and shut off once or twice an hour, but I think that’s just it working as I intended. As to whether “as intended” is the correct way or not, that’s another question :smiley:

5W doesn’t sound like much, but with 4 valves for 24 hours that’s a quarter of a unit, 4p (for me).

That’s why you’ll have to choose carefully between the NO or the NC valves depending on how much use the radiators has.

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