Launch an external temperature sensor for the Smart Radiator Thermostats

I'm very happy with Tado overall, apart from the performance of the Tado Smart Radiator Thermostats. I’m finding that due to the way the Tado Smart Radiator Thermostats work, they heat up a room very, very slowly, and sometimes fail to get a room anywhere near the desired temperature. I've noticed that after they turn on the radiator, they seem to then quickly turn it off as it thinks it’s reached the target temperature, when in fact it hasn’t and it's just due to the proximity of the temperature sensor to the hot radiator.

I performed a test with the bedroom in our house, it’s a simple rectangular room, measuring about 3 x 3.5 meters with a single radiator. The doors and windows were kept closed throughout:

The room was at 19ºC at 11:30 am and I set Tado to heat it to 22ºC.

The radiator heats up, but the SRT temperature sensor quite quickly reads 22ºC so Tado turns the radiator off. However, the room is actually only at 19.5ºC (measured on a 2nd thermometer elsewhere in the room), right next to the radiator it is 22ºC but not elsewhere in the room.

You then have to wait for the temperature by the radiator to cool down (about 30 mins), before the radiator will eventually heat up again, but then the whole cycle starts over again with the radiator quickly shutting off.

This means it takes a very long time for the room to get to the target temperature (and sometimes not at all), as the radiator keeps getting turned off before the room temperature is anywhere near the target temperature.

After 6.5 hours the room had still not reached its target temperature of 22ºC and is only at 20.5ºC at 6 pm, because Tado kept prematurely turning off the radiator.

Please see this graph:


Which shows the 22ºC target temp in green, the actual room temperature (measured by another thermometer at another point in the room) in orange, and the Tado graph showing it constantly turning the radiator off.

You can see from the graph that this isn’t simply solvable by setting a “Temperature Offset” in the app, as when the radiator isn’t warm the Tado thermometer more accurately represents the room temperature (and is often actually under-reporting it, not over).

However, to see what would happen, I went ahead and set an offset. As the Tado was effectively over-reading the temperature by about 1.5ºC, I set an offset of -2ºC. I then left it for over 2 hours to settle, and this was the result:

As you can see, an initial boost helps gradually raise the actual room temperature, but as it still quickly turns off the radiator, the actual room temperature only reaches about 21.3ºC, still not even close to the 22ºC target.

A side effect of this offset was that the next morning, when the radiator had been off overnight, Tado thought the room was at 16ºC when it was actually at 19ºC, and caused it to needlessly turn on the radiator. So as you can see adding an offset doesn’t solve the issue and actually introduces more problems.

In my opinion, the SRTs need to be much, much cleverer, learning the characteristics of the room and then ignoring any initial overshoot in temperature to allow the actual room temperature to get to the correct level.

Either that or Tado need release a small, cheap (~£30) temperature sensor that can be placed in the room away from the radiator to give much better results. I know you can use a Tado Smart Thermostat, but at £100 these are too expensive to put in every room.

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  • mw9342mw9342 ✭✭✭

    ..................+1

  • +1 - the Smart Thermostat is too expensive to use for this role, and there are rooms where I would never want to have a display or control interface (kids bedrooms!)

    A simple remote temperature sensor at a reasonable price would be great.

  • +1 - external temperature sensor would be ideal.


    We have odd shaped rooms with varying temperature profiles.

    It would be better for us to have a sensor near where we need it and slave it to the TRV.

    Ideally the room would either average between the TRV and the remote or use the remote sensor.

  • edited February 27

    +1

    This is exactly what is causing me to put off buying Smart Radiator Thermostats. I had wondered about the sense in placing a thermostat so near to a radiator (let's be clear, nobody recommends placing a room thermostat near a radiator) and I have heard tales like this elsewhere.

  • Hey guys, I’ve been having the same problems as you have described in one of my bedrooms.

    Been experimenting over the last few weeks with various things as it’s been driving me mad as to why the TRV was calling for heat so often, now I think I’ve found a solution as results look very promising, at least for me anyway.

    The room in question is a small box room 3.3 x 2.4m with a single panel rad 600 x 900mm.
    The TRV is (was) fittted vertically with a -3 deg off set to achieve required temp on the other side of the room, measured using an electronic weather station remote senor that has only a 0.3 deg difference to the TRV.

    Today I turned the valve and TRV so it’s horizontal, what a difference this has made.
    Off set from TRV removed, temp even across the room and boiler on a lot less often.

    I would show you screen shots of the graphs but at the moment I can’t copy them to this thread.

    Hope this helps.
  • jcwackyjcwacky ✭✭✭

    @MarkC That's a good tip (if you're in the position to be able to change the valve that is). I too noticed that even moving the TRV a small distance from the radiator had large improvements. I think it also varies on your radiator type. If you have a new one, with the side panels, even these can help stop some of the heat coming out sideways towards the TRV. I was going to experiment with adding a small reflective panel between the TRV and radiator.

  • I like the idea of a cheap room stat, I would buy them if reasonably priced. I have 11 x TRVs and would like to add perhaps 3 cheap stats for the most used rooms.

  • AdzLillAdzLill ✭✭✭
    +1 for this....

    I work in the HVAC industry and wouldn’t ever dream of placing a temp probe right next to your heat source.

    I’m having the same problem and this solution would fix the issue. No way am I going to spend another £99 on a smart thermostat when I’ve already spent £59 on a ‘smart’ radiator stat.

    COME ON TADO
  • I think 2 point calibration for the temperature offset might help here - an offset at high end to ensure the room reaches the target temperature and an offset at the low end to prevent premature turn on

  • @GJWalsh started this thread requesting 2-point calibration. @jcwacky, I suggest you have a look because it would circumvent the unwanted consequence of setting a large offset that you both have experienceed:

    "A side effect of this offset was that the next morning, when the radiator had been off overnight, Tado thought the room was at 16ºC when it was actually at 19ºC, and caused it to needlessly turn on the radiator. So as you can see adding an offset doesn’t solve the issue and actually introduces more problems"

  • Absolutely +1

    I also reported it to customer support and they told me to purchase a thermostat for each room. It's crazy but is the only way at the moment, so +1 also for GJWalsh.

  • Without wishing to confuse, I’d also suggest the algorithm should take into account measured temperatures from all/multiple smart radiator thermostats in a zone. Different radiators will warm up a different rates and this may enable the system to learn better and “balance” the heat output across the zone to avoid hot/cold spots. Throw the data into an AI engine!
  • I've also got this problem on vertical valves - it does not affect my horizontal valves. I've got a vertical in my bedroom and typically I hear it come on, and within 5-10 mins it goes off again... The radiator is barely warm and it's gone off because its been influenced by heat from pipe / near radiator edge. I've currently got a sock wrapped around it to try and stop this!

    Suggest "damping" the reading somewhat after calling for heat as currently its not handled well. Of course trying to isolate the temp sensor from the radiant / conducted heat would help, but will never be the whole solution.

    Perhaps allow setting a deliberate "overshoot" so heating comes on at set point, but doesn't go off until set point + overshoot. Not ideal, but easy to do in software.

    A cheap external sensor would also be useful approach, but think software fixes most applicable to greatest number of users.
  • jacoscarjacoscar ✭✭
    What about an external (wired) cheap temperature sensor to be connected to the smart trv?
  • I believe they do a remote thermostat which I assume could be placed the rooms, but these are priced at around £100 each, 3 bedroom house, 2 WC's,1 kitchen, 1 dinning room, living room, hall.
    So taking into account of the original cost of the tado, £200,the TVRs x8 and extra remote thermostats x8 it would cost a fortune, and never recoup the saving from the heating.
  • @c12ble

    The only Tado product that I think qualifies as a remote thermostat would be an 'additional' smart thermostat.

    Unfortunately the way this currently works if either the additional thermostat or a smart TRV calls for heat then the boiler would fire up. Furthermore if the TRV decides it is 'satisfied' then it would locally turn off the radiator regardless of the temperature reported by any smart thermostat.

    For this to work Tado would have to add additional software support to tell a TRV to ignore its built-in thermostat and instead to base its behaviour on a specified external thermostat which might be a standard Tado additional thermostat. (Hopefully Tado will add support for either generic smart thermostats or release an additional product which is a stripped down thermostat and hence much cheaper.)

    Even if a new cheap external thermostat was provided it is not an elegant solution in that it is yet more devices to setup and more batteries to worry about. However at least it might be possible to only have one per room even if a room has multiple radiators. Arguably this approach would be beneficial also for those people with wooden radiator covers. I would presume a wooden radiator cover would result in distorted readings for both vertical and horizontal TRVs.

    This hypothetical external thermostat would have to be ignored by the boiler itself i.e. the master smart thermostat and/or extension module and purely used by the TRVs. Otherwise you would end up with the current situation of it potentially calling for heat when the TRVs report satisfied. The boiler then would be heating the water in the pipes but not the radiators and still wasting energy.

    It seems there is a genuine problem currently here at least with vertical TRVs. If Tado cannot solve this purely in software by clever compensation calculations then cheap external thermostats as above seem a good solution. It could be an additional source of revenue, either by happier customers or by selling these hypothetical sensors.

  • jcwackyjcwacky ✭✭✭
    @jelockwood
    “Unfortunately the way this currently works if either the additional thermostat or a smart TRV calls for heat then the boiler would fire up. Furthermore if the TRV decides it is 'satisfied' then it would locally turn off the radiator regardless of the temperature reported by any smart thermostat.”

    Incorrect. When you add an additional thermostat to a zone, you set which device should be the temperature measuring device. Each zone only uses one device’s temperature reading and ignores the others.
  • jacoscarjacoscar ✭✭
    @MarkC when you say horizontally, do you mean at the bottom of the radiator but pointing sideways (so you just reversed the valve body) or pointing towards you?

    I’m fitting new pipes and I’m trying to figure out the best way to orient the TRV (still have to buy them); also my Trv will be at the top and not at the bottom of the radiator
  • jacoscarjacoscar ✭✭
    I’ve just asked tado which valves are better for room temperature measurement (vertical vs horizontal) and this is the reply


    We spent considerable time on this, which is why the Smart Radiator Thermostats have 2 sensors, one near the outside edge, one near the valve, to differentiate what the source for a change in temperature is. We have found that this works very well for nearly every installation so far. We are also looking into alternative strategies for the few corner-cases though.
  • jcwackyjcwacky ✭✭✭

    the Smart Radiator Thermostats have 2 sensors, one near the outside edge, one near the valve, to differentiate what the source for a change in temperature is.


    Interesting! This is the first I've heard of this, thanks for posting. Upon inspection of the SRT I can only see a hole for one temperature sensor, on the top, above the display. So I wonder where the 2nd sensor is.

    Also, thinking about it, with the sensor on the top, centered above the display, with a SRT which is to one side of the radiator, this isn't the furthest distance from it. You could rotate the SRT 90º clockwise (if on the left of the radiator) or 90º counter clockwise (if on the right) and this would result in the sensor being even further away from the radiator. So could be worth a try if you don't mind the display being harder to see.

  • FrankFrank | Admin

    Hi jcwacky,

    The second sensor is inside the body of the thermostat, located so as to measure the temperature of the thermostat / valve.

    BR

    Frank

  • [quote]Either that or Tado need release a small, cheap (~£30) temperature sensor that can be placed in the room away from the radiator to give much better results. I know you can use a Tado Smart Thermostat, but at £100 these are too expensive to put in every room.[/quote]

    +1 to this. In the Z-Wave world there are plenty of temperature sensors in this price bracket, so I think it's reasonable to expect something similar from tado. If tado don't want to actually develop and sell such a product, then at least make it possible in the software for us to link a Z-Wave device (perhaps through integration with SmartThings).

    As others have said, this is something that is holding me back from going out and buying multiple tado smart radiator thermostats, so this is costing you sales guys!

  • I was thinking; instead of a 100£ Tado Thermostat, you can use another Tado TRV just to measure the temperature: you can assign multiple TRVs to a single zone and decide which one will measure the temperature; obviously both will open and close but only one (the one NOT measuring the temperature) will be on a radiator
  • jcwackyjcwacky ✭✭✭

    @jacoscar Correct, I did this for quite a while, I had a Tado TRV sitting on my beside table, and it worked great to avoid the problems I mentioned above.

  • So, we just tried our Tado system last night when the temperature dropped for the first time since installing it a month ago. Radiator’s went on for 10 minutes Tado thought the temperature was 24 degrees. A room thermometer said it had got to 21 degrees. I can see this being a problem in the winter months.

    It’s only numbers so you should just be able to turn it up, but the limit is 25. So that’s out too.

    I can see the radiator thermostat’s being removed from some radiator’s to improve functionality. Which defeats the object.
  • jacoscarjacoscar ✭✭
    edited August 16
    I just changed half of my radiators and altered the piping as well; I now have the flow entering the top of the radiator and the return coming out at the bottom at the opposite side (this is the most efficient way and also how the radiators are tested for their power output); so on these radiators I’m using horizontal valves at the top (pointing towards the center of the room)
    They work ok, but they would work even better with the valve pointing towards the corner of the room.

    I also tried installing my vertical Tados on my older radiator (with bottom connections); it didn’t work; I even tried insulating the pipe below the valve, insulating the side of the radiator, but it didn’t help.
    I ended up inverting the TRV bodies so that the Tado head is now horizontal (pointing towards the corner of the room, but still at the bottom of the radiators); it doesn’t look nice, but it works

    Conclusion: always mount your Tados horizontally unless you have an additional thermostat in that room
  • I will love to have a Tado Remote thermometer so i can set one of my Radiator Thermostat to use the temp from the remote thermometer sensor.


    Reason is the i have 1 Radiator thermostat close to a pc, and when i use my pc, the thermostat thinks it's 28-30 degrees, but the room is maybe only 20-21 degrees. The thermostat will never turn on, when i use my pc. So if Tado made a remote thermometer, i could use the temp from that to control the radiator thermostat.


    It will be amazing if Tado could make something like that one day :)

  • Good afternoon all.

    I am newbie so please apologise my dumb question hereinafter and maybe wrong thread I entered.

    Just installed Smart Thermostat V3 and 12 SRT V3 as well. Met with most of earlier mentioned issues but I think it is too early for evaluation. One thing however is creating my headache. I can do whatever with SRT in any zone, boiler just ignore any signal for heating. I can only wake up my Junckers-CerapurComfort-28 (CW400) by activating temp on Smart Thermostat - the main controller. Seller told me I must contact TADO (that I did few times..) for remote activation of zone heating. Was he correct by saying this or I have done something incorrectly during installation/adoption process?


    Thanks and cheers, Marian

  • Good afternoon all.

    I am newbie so please apologise my dumb question hereinafter. Just installed Smart Thermostat V3 and 12 SRT V3 as well. Met with most of earlier mentioned issues but I think it is too early for evaluation. One thing however is creating my headache. I can do whatever with SRT in any zone, boiler just ignore any signal for heating. I can only wake up my Junckers-CerapurComfort-28 (CW400) by activating temp on Smart Thermostat - the main controller. Seller told me I must contact TADO (that I did few times..) for remote activation of zone heating. Was he correct by saying this or I have done something incorrectly during installation/adoption process?


    Thanks and cheers, Marian

  • +1!

    With this feature, I just would change everything regarding heating to Tado.

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