[Released] Launch an external temperature sensor for the Smart Radiator Thermostats



  • Treefitty
    edited October 2019
    @Mjjjo i understood it that you set up the thermostat first and then the SRTs should see there is a stat when you set them up and use it to call for heat. However I am not 100% sure in that.

    What I’d do know is that SRTs can be linked to set off a specific smart thermostat. So if like me you have two Valve controlled zones controlled by two smart thermostats the SRTs will use the relevant smart thermostat to open the relevant valve supplying that SRT and call for heat.

    You can not do this yourself however you have to get support to do it for you.

    In essence from what I understand the SRTs, smart thermostats and extension kits connect to the bridge. They back end systems decide what’s happening and then act accordingly. If you don’t have a smart thermostat or extension kit all they can do is operate the valve. If you do they can signal the smart thermostat or extension kit to call for heat but they obviously have to know it’s there for that and which one to use. Additionally the smart thermostats can call for heat manually with no connection because they are in essence just like any other thermostat and can be made to call for heat directly from its own controls.

    Hope that helps
  • Vertigo
    Vertigo ✭✭✭
    edited October 2019

    BTW, I may have a complicated and clumsy work around. Using openhab. Im just starting to get in to it, and its not for everyone, but it can connect to most things, so just about any smart sensor should work, and also to Tado.

    For tado it can read most things including current temp (hey, who knew, the SRTs do give a read out with 1 decimal place!) and target temp for each device. It cant set everything, so no away/home override :( but it can set temperatures, so it should be possible to script something that takes the room temperature sensor, compares it to the tado sensor, and if the tado sensor reads a lot higher, and the room sensor is below the target temperature of Tado, then increase the target temperature by a few degrees until the room sensor measures you achieved your goal.

    You may be able to do the same with IFTTT.

    Edit: the script would have to remember the original target temperature and set it back after it accomplished its goal, and this may cause problems when the Tado scheduler changes (you can not read the schedule afaik) so ideally you would account for that too. Or just do or duplicate the scheduling for that room in openhab/IFTTT. Not ideal, but perhaps better than freezing.

  • I fear they are going to take all the good ideas and release them in a new V4 update and charge for the privilege! They haven't changed one thing in over a year. Surely they wouldn't make that mistake again? Would they?

  • What about wireless tags and IFTTT?
  • Signed up just to comment here. +1 tado! Especially when you are unlucky and have a radiator place up at the ceiling. I need an external thermostat to place lower in the room!
  • kkupe
    edited November 2019


    It's needed! Happy to see it is one of the most requested ideas.

    As I know putting a Smart Thermostat wirelessly to each room is not possible because extension kit only allows one device to connect wirelessly. And it is more than €100 because you have to buy also extension kit. This is what I am told via a support chat conversation. Correct me if I am wrong.

  • +1 It would be a great addition to an already impressive system.

    Can we at least know if you have something of the sort on the road map?

  • where is TADO on this? do they ever read or reply in this Forum?

  • We 100% need this! Hoping for a response soon Tado, but not getting my hopes up.

  • Hi all,

    I wanted to run an idea with you.

    Do you think would work to leave the NOT smart valve to the radiator and the SMART on the night table.

    and switch ion and off the radiator via the smart thermostat in the living room when the SMART valve in the bedroom reach the desired temperature.



  • @Mrpinty You'd have to set the bedroom's SRV as being in the "living room" zone as you can only set one "temperature measurement device" per zone. Then this would mean that the living room wouldn't heat up if the bedroom was already at temperature.

    You can, however, buy a 2nd SRT for the bedroom and place it on your night table and set it as the bedroom zone's measurement device. This solves the issue for less money than buying a full extra thermostat.

  • andreig1978
    andreig1978 ✭✭✭
    edited November 2019

    Hi Luca,

    You would probably get into a situation where the smart TRV (used as a thermostat) will request heat causing the boiler to fire and the NON smart TRV will decide it is warm enough and switch off the radiator.

    As @jcwacky already said it can be done with two smart TRVs because they synchronize.

    Or we can keep pushing for an external temperature sensor to avoid using TRVs as paperweights 😄



  • Another idea, suggestion Tado are still ignoring.

    Anybody else feel like the bought the wrong product
  • Anybody else feel like the bought the wrong product

    Yeah, me. Contemplating switching to popp/lc13 z-wave TRVs on home assistant. But clearly thats not a solution for everyone.

  • +1

    Overall I'm impressed with Tado, it's significantly better than having a non-smart system. But the "temperature offset" feature is far too simplistic to deal with the problem of measuring temperature right next to the heat source. It works well in some of my rooms, but in others the true temperature offset varies by up to 6 degrees throughout the day.

    The cheapest solution is to buy an extra TRV, tape it to your wall and use it as the heat source. Obviously this is a complete waste as the main function of the TRV is being wasted. Tado's suggestion solution is even more wasteful however, requiring a device that costs £40 extra to do the same job.

    Tado - Please create a simple thermostat by taking the valve components out of your TRV. It should cost less than the TRV and still have plenty of margin left for you.

  • +1
    However we all know tado will never do it. A simple software futures takes YEARS if at all to be produced what for a hardware device.
    Second why would they bother producing a cheaper sensor when people are buying their overpriced STRVs or even worst the Smart Thermostats? It's clear to most of us, but not Tado.
    To another post that was asking where is Tado on this topic? - The ONE part time employee involved with reading or eventually replaying to post on the WHOLE community portal is off sick.. Yeah it is one person logging in with different names!
  • With all TRVs the inherent problem is where the temperature is measured. Setting an offset is not a solution but an unsatisfactory work round.

    I have sacrificed a Tado TRV to act as a remote sensor and room primary measurement device that sits on my bedside table.

    So clearly Tado *could* produce a remote sensor slaved to a control-only TRV. This would be an ideal solution, separating for example the head from the TRV body at the cost of an additional sensor battery and WiFi electronics.

    I think Tado are well aware of this but the additional tooling and production line costs are prohibitive so it is unlikely to happen. Perhaps someone knows of a similar system that has such split sensor/control TRVs?

    I ask because Tado clearly have a product roadmap and business model that is geared to maximising revenue from their already sunk investment. I would bet their R&D guys are frustrated, if indeed they still have such a department. However the evidence is Tado do not have the desire to invest in improvements at the moment or are so secretive they will spring a surprise in the future.

    I see the answer as market pressure. I will abandon Tado as soon as I can get an equivalent system with a decent app/graphics, remote sensors and complete preferably open system with control in my hands (i.e. no data held by the manufacturer).

    Tado should go open with their protocols etc., produce hardware only and let others do what they are unwilling to do.

  • Nicely described, very important request.

    I think most important things have been said here, I have nothing to add.

    Looking forward to see this coming, will absolutely buy it for a reasonable price.

  • Vertigo
    Vertigo ✭✭✭
    edited November 2019

    For about 10 euro you can buy wireless temperature and humidity sensors. eg:

    All thats needed is software support for third party sensors, or heck, tado can just rebadge them and sell them for 30 euro, no tooling necessary. They can do the same with window/door sensors, surely works better than the software detection, and they cost like 5 euro.

    Alternatively, you can already do this yourself if you really want using home assistant, provided you have a sonoff or similar rf to wifi bridge and you dont mind doing everything in home assistant, forgoing tado app and functionality.

  • I would be happy to go the home assistant route with a remote sensor but I would be concerned about what goes on behind the scenes with the Tado system.

    Presumably schedules and settings are held by Tado. I also presume Tado sends control commands to the boiler and TRVs based on sensor values, the boiler state and the schedule. It is the algorithm that does this that would need to be programmed by the user.

    As a retired software engineer that doesn't frighten me but I would need to know how the boiler is controlled. I don't mean the protocol but the rules.

    The danger is mis-programming and having an inefficient system or worse. This is not a trivial exercise.

  • Vertigo
    Vertigo ✭✭✭
    edited November 2019

    If you use tado's wall thermostat (and/or extension kit) to control the boiler, even with home assistant you wont get control over the boiler algorithm, it will still be tado's. You basically gain control over its temperature setting. Just like when manually adjusting the temperature on the device when its in away mode or offline. Hysteresis or cycle limits or a PID loops, if any, those will still remain whatever tado programmed in the wall thermostat . I dont think those are rocket science, but unless you plan on building your own thermostat, its not our concern.

    Do note that you can disconnect from tado cloud by using the homekit protocol in home assistant, gaining you direct control over the temp settings without going through their cloud cloud. What you would lose is the weather/sunlight compensation factor and those things. I honestly do not think they make a big difference. Prove me wrong by pulling the ethernet cable from the bridge or asking a homekit user. I think a bigger gain can be had doing things tado currently does not seem to do. Like looking ahead in the schedule and if a lower temp setting is coming up in a few minutes, already allow a larger downward hysteresis. You cant control the hysteresis directly but you could fudge that by adjusting the temp setting more gradually.

    And of course, depending on your family situation you might save a lot more by doing stuff like creating different home/away zones for different people or using actual window/door sensors rather than tado's open window guess work. And create your own home/away logic and geolocation solution.

  • With Nest you get 3 temperature sensors (T5001SF Nest Temperature Sensor) for less than $100 place them around your house and control the temperature in every room. and they are small, not the big thing that is Tado thermostat.

    Sure Tado will do the same thing ASAP not to lose customers to Nest: right Tado?

  • they could just allow us to setup a custom hysteresis for each room, without asking for even more money.

  • Agree with most comments.

    +1 for thermostats independent of valves without the cost of the full wall thermostat.

    I would also suggest room temperature could be controlled by more than one TRV instead of a selected device as now. Often the temp gradient from one side of a room to another (even more so for a zone eg bedroom and dressing room) could be used to balance out the impact of localised heat on TRV sensing. No new hardware needed, just a little code.
  • We should celebrate the 100th up-vote.
    Who's bringing the champagne?
  • Heya all,

    Some very sensible suggestions and findings here... indeed a simple external sensor would be most welcome in order to accurately heat certain rooms. Mine are mostly fine since checking with an external sensor, but our bedroom is off by -2 to -3 degrees when close to my target temp and i also get the weird offset when things are off and cool down in the morning as the OP has shown.

    So, do you think Tado could calibrate and apply a curve of sorts to the offset? So, we set a min and max offset for when it's off and settled and for when it's on and heating?

    For mine, i'd like the offset to scale down back to zero when it's cold and scale up to -2 or -3 when it's heating closer to a nice temp of around 20.


  • This would also probably work for me too. I still prefer the external temperature sensor solution but your proposal is definitely better than the simplistic offset sulution we have now.