Any TRV suggestions?

Yep I’ll share all my rules etc - just need to sort out how I deal with “Away” mode with the Nest, which I’ll hopefully get sorted over the next few days :slight_smile:

I have 2 nests - have a few rules tied into away mode already. What probs have you got?

Managed to set up an mqtt/sonoff - flashed ota with Tasmoto. I like it!!

Hi all, very new to this, I’ve been thinking about this for a while, looking for a cheap solution, was looking at this thread and have a question.

If you need to run power to the trv, why use the sonoff, couldn’t you just go back to a relay board?

Sonoff is just a cheap relay with some clever firmware onboard

Guys, thanks for all the posts above, just been fighting with TRV’s and would rather cook my own solution!
@Confused - Could you do your writeup :slight_smile: - avid Sonoff user here!
Also does anyone know of any PWM models so one can reduce the flow instead of On/Off - Have a nodemcu unit that i have almost fully working to control PWM gating so if someone finds a PWM model !
Any links to what models of actuators you are using - please do post, all the ones above are unavailable.

Thanks !


James - I use on / off via a Sonoff and a £12 trv - I switch on when temps are 0.5 below target and off when temps reach target.
My one room cycles once per night, the other, three times - but it’s more than sufficient - wouldn’t bother trying to be any more granular

Cool, which trv are you using ?
I have been looking for some mains powered ones - threr are lots - not sure which to trust (have 14 rads to wire up!)

£12 that’s very cheap

FWIW I have 1x Devolo (Was my first TRV) which is really good at keeping temp (The variation is very small) but was an absolute PITA to get included and installed. Like hours and lots of cursing. It also feels a little less physically robust than I feel it should. It does report back temp, so not a complete

I also have about 4x Eurotronics Spiritz TRV’s. They feel better built. Way easier to access the battery compartment, the display is clearer, controls are better. It also reports back temp. And was way easier to include.

I really like this idea. Looks cheap, reliable, platform independent and easy to realise.

I think Confused/Garry Mitchell’s idea of DIY modulation is really cool. From what I understood the valve is controlled by a wax expanding/shrinking depending on whether power is On or Off, taking approximately 3 minutes in total to go from fully expanded to fully shrunken. The time it takes also depends on ambient temperature it seems. Mind you, it’s close to the valve, so it the ambient temperature there might range from 15C to 50C/85*C, depending on max supply temperature of your boiler, heating on or off, and heating duration. This might really be of influence. But you could imagine something like this.
Mode 0: Sonoff Off
Mode1: Sonoff alternating 45s On, 135s Off (alternating for as long as valve should be open)
Mode 2: Sonoff alternating 90s On, 90s Off (alternating for as long as valve should be open)
Mode 2: Sonoff alternating 135s On, 45s Off (alternating for as long as valve should be open)
Mode 4: Sonoff On

Not sure if it works. And not sure if the Sonoff and the Actuator will like the alternating treatment, but it could be a solution… The lower your boiler supply temperature, the less you will likely need this modulation option.

Numbers above all based on 3 minutes to go from fully open to fully closed. You can check how long it really takes for your actuator by just turning it on without it being mounted, and just see how long it takes to fully expand/shrink. Once in the middle of the room (+/- 20C) and once while placing it on a tea towel or something on top of the radiator fully opened (>50C)

@Confused Thank you very much for sharing! Some questions though: Do you know what’s the Central Heating (maximum) supply temperature in the case of this image:

The fluctuation of 1*C are quite large…

And what’s the latest news? Still happy with your setup? Did you tweak it?

@dabachata The Operation you described above is common in professional room temperature control. I have a LCN System installed (from German firm Issendorf) which uses 230V (AC) thermo-electric control for radiator control and under-floor heating valves (called LCN-AVN). These valves are controlled by the control module, which could be parameterized to a mode called “PPS” (german: Puls-Paket-Steuerung / engl: pulsed packet control). this mode is an adaption from PWM for AC voltage. You specify a time frame (less than the maximum open/close time of the valve) and the control calculates the on- and off-time of the output for the valve.

For your example it is
Mode 0: 0%
Mode 1: 25%
Mode 2: 50%
Mode 3: 75%
Mode 4: 100%

The LCN system calculates the on-/off-time via a regulator with a resolution of 2% or 0,5% (dependend of the module)…

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I have used exactly the same solution. Thermal actuator normal closed and Sonoff.
I control 6 radiators around the house with mysensors temperatures and humidity sensors in each room.
I control the target temperatures and times with node-red and the ramp thermostat node.
I have all the different profiles for each room in a json file the node-red read and applies the profile to the node according to the day of the week and/or house mode (AWAY, HOLIDAY…)

Very reliable and I have touched any of the devices for months.


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@vzorglub You use simply On/Off and not the above mentioned “Puls Paket Steuerung” / “Puls Packet Control”?
Sounds like you have City/District Heating, right?
Do you know what the heating water supply temperature is? (The temperature of the water before entering the radiator.)

I’m very interested to know the temperature fluctuation you experience with this setup. So say your target temperature is 19.C, how much does is fluctuate around 19.C once the temperature in the room is already near target (e.g. target 19.C, range 18.6C-19.7C) Depends also on the temperature of the heating water flowing through your radiator, so that would be great to know too.

@imhofa Great to hear it already exists :slight_smile: Means that the alternating treatment doesn’t really hurt the component, otherwise it wouldn’t be used in professional setting :relaxed:

The valve are simply on/off
There is an offset of +/- 0.5 in the thermostart rules in OH and I don’t vary more than that
We can’t feel it

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@dabachata The difference between the two mentioned methods are:

simply on/off -> bang-bang control (german: Zweipunktregler)
The control switches on and off at the given temperature and Hysteresis. E.g. turn on below 20°C and turn off above 21°C. This results in full flow or no flow for the hot water. The Regulator process is perfectly described on Wikipedia:–bang_control

Pulse Packet Control:
Electrically (for the switching relay) the stress is the same as for bang-bang control, because you also switching more often (about every 2 or 3 minutes). But the hot water for the radiators are more in continous flow with this Regulation, because the hot water flow is nearly constant over time if you are in the area of the set point temperature.

bang-bang control is easy to implement and don’t need any further knowledge of technical details (e.g. does not care about opening/closing time of the TRV) but results in a bigger error signal around the desired set point.

Pulse-Packet-Control is not that easy to implement, because you need the additional time-based on/off cycles and this time base must be suitable for the used TRV. The result is less error signal around the desired set point and is more convenient for the central heating system.

I’ve done a write-up of what I’ve done here:

That image may be from when I had a 0.5 degree hysteresis - I’ve dropped this to 0.2 now as my wife was coming to me as it was dropping down to the bottom of that degree swing and saying “is the heating broken?” - she’s complaining a lot less now it’s a 0.4 degree swing!

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You state the followingh about your Nest : which I’ve disabled all the smart/learning stuff on, and am simply using it like an On/Off switch

How do you just turn it on/off? Is there a switch that you can trigger to start heating or do you set a higher temp on it?

I have not set any scheduling, disabled home/away mode, and I simply send it one of two desired temperatures - in my case it’s 15 and 24.

When I send 15, it’s “off” - but if the temperature does actually drop this low in the room where the Nest is located, it will switch on, and the radiators in the house without individual control will come on to stop the whole house getting too cold.

When I send 24, it’s “on” - the maximum any of my set-points in various rooms are is 22, so 24 should be enough over this that it won’t turn off again unless I ask it to.

You may need to amend/tweak this to suit your own house and the room your Nest is located in.

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We offer a similar solution with the 24v versions of those actuators, with a local small relay, but we run a 24v power & data bus cable as discreetly as possible around the property.

That same bus data line then links into the Velbus glass control panels for full temperature target control.