Heating power percentage and calling for heat

The API exposes a heating power section:

   "heatingPower": {
     "type": "PERCENTAGE",
     "percentage": 33,
     "timestamp": "2022-03-11T07:15:43.873Z"

This is presumably used to render the 1/2/3 flames in the UI. But my heating system is just a plain old boiler that only supports binary calling for heat/not calling for heat states. Does anyone know at what percentage value the system will start calling for heat from the boiler?



  • Did you manage to find an answer to this? I just bought a new thermostat and it's trying to heat my house at 17%... but that doesn't seem to have any effect on my boiler that just have an ON/OFF status.

    Is there a way to change tado's behavior to work with this kind of boilers that don't support heating power?

  • Is the thermostat holding the temp plus or minus 0.5 C ish, if so that’s relay control…..

  • It's the first time of the season the temperature has dropped below the defined temp. And yes, it has dropped less than 0.5 C below the desired temp, but tado reports will say that it has been heating for almost an hour when it's not true, the boiler never actually started heating

  • It did not drop much below 20 C and eventually raised. The fact that Tado reports the boiler firing is false, it does not send an on signal to the boiler until much later. It Is how the non opentherm/ebus control works. Not transparent.

  • I have 10 SRT's 1 Wireless Thermostat and 1 Wireless Temperature Sensor over 9 tado° rooms.
    5 of my SRT's have no Zone Controller and are therefore INDEPENDENT.......which means that they CANNOT "call for heat" from the boiler......however tado° still classes this as gas usage.....utter rubbish......therefore any data provided can only be at best..... a "guesstimate" and when you consider that tado° has absolutely no idea of my household configuration etc...... then any estimate of predicted usage is likely to be "smoke & mirrors" (imho)
  • Seeing that these IQ reports are part of their premium paid features, they should really put more effort in providing better information
  • andyblac
    andyblac ✭✭✭
    edited November 2022

    @GrayDav4276 and to make it worse, if one of your SRT's is open due to low temp, Tado˚ system thinks it is still calling for heat and using gas, when in-fact it's not using anything at all, as your other WTS's are not calling for heat, at least it used to work this way.

  • @andyblac
    I thought that I covered that in my previous post......if I didn't.....then can I say that I totally agree with you 🙏
  • cbd20
    cbd20 | Moderator
    I've noticed an interesting (and annoying) quirk so far this heating season relating to the heat requests from the smart radiator thermostats (SRTs). I've had tado installed for a number of years in a relay configuration and this is the first year I've noticed this particular problem...

    As has been observed here, a single room making a low heat request will typically not fire the boiler at all. However, if several rooms are calling for low heat then the boiler does indeed fire up.

    However, in my case for this heating season a low heat request doesn't actually open my valves enough on the radiators to actually allow any hot water to pass through. What then happens is, because several rooms are requesting low heat the boiler fires up but then tado keeps periodically calling the boiler because the rooms requesting the heat never actually heat up. Eventually, tado will notice those rooms not warming up and increase the heat request and the valves then open enough to allow hot water to enter, but this can take up to an hour for tado to notice!

    I have several non-tado equipped radiators so the heat always has somewhere to go, but it's a waste of gas, as the rooms actually requiring the heat aren't getting satisfied.

    I believe this relates to one of the SRT firmware updates released earlier this year, where it was stated on this forum somewhere that their developers realised in "most cases" they don't need to open the valves as much, and this helped battery life. However, clearly with my specific valves, there's an amount of movement required before it opens at all, so it's having a negative effect on how my system operates.

    I've been in contact with support and they've tried a couple of times to change the minimum opening parameters on the SRTs (which to be honest I wasn't aware they could do, and am still sceptical as so far I've not seen any improvement).

    It's an ongoing discussion with them at the moment.
  • @cbd20
    You could always try removing the batteries from the SRT for 1 minute....and then go through a full mount and calibration.....not sure if this will help, but it's possibly worth a shot.
  • cbd20
    cbd20 | Moderator
    @GrayDav4276 yup tried that and the two times tado have allegedly "updated the opening parameters" they've remotely forced a recalibration too. Sadly no difference.
  • @cbd20 Same problem here. I have all-but-one radiators with SRTs. The one has a standard valve because I don't have the loop with a pressure valve. Pretty much anything under 15-20% heat usage by SRTs won't get any hot water to my radiators.

    The annoying fact is that that radiator is in a hall which is now the hotest room in the house...
  • cbd20
    cbd20 | Moderator
    @Hiavata I've had my radiator thermostats installed for just over 2 years and this is the first time I've really noticed it - but I'll caveat that by saying I'm watching my heating system like a hawk this year to monitor how much it's costing me, so possibly I'm just being more observant this year.

    As said above, I've got an open discussion with tado support about it. They've tried changing the minimum open percentage of them remotely twice - at least that's what I was told. The valves did recalibrate after each attempt but sadly it hasn't made much difference.

    All of mine are fitted using one of the adapters with the pin extenders. They've now asked me to try a different length pin extender to see if that makes a difference.

    I guess the thinking is that my particular valves have got a certain amount of movement before they actually start to open. By trying a shorter extender pin I guess they're hoping it'll actually be too short to completely close the valve in the first place, and therefore it'll be closer to the opening point earlier in its travel.

    I can't convince myself that will work, but I'm intending to try it at the weekend when I've got time to experiment.
  • Mine is the same.

    Care and protect racking up heating hours when the boiler isn't on. It's a joke.

    The logic is basically wrong when they call for heat. They turn down the radiator valve too far. I'd try them on independent. Or calibrate them and unscrew them on the mount a few turns as that also increases the minimum open amount but I generally found the Tado worked this out and just stepped back even more so the gains were minimal. I definitely find independent works better.

    If they call for heat and don't get it (because they can't turn the boiler on) they turn up the heat demand more so it works better when they actually get it as valve is more open. I find a temperature range is fine rather than constantly flip flopping between 2 tight values in a room. A 2c difference between warmest and coldest is generally ok. 1.5c is better but most of the time you don't actually feel it being too cold until just before the main thermostat gets down to the trigger temperature.

  • cbd20
    cbd20 | Moderator
    Just a quick update on this. I finally got round to trying a shorter pin extender in the adaptor for my radiator thermostats. Unfortunately the pin was then too short, and the thermostat was unable to close the valve enough. This led to the opposite issue of the radiator heating up even when not requiring heat.

    I've reverted to the original pin extender.

    I personally don't have an issue with a single radiator requesting low heat and not firing the boiler. Yes, it erroneously adds to the Care & Protect screen but to be honest I more or less ignore that anyway. It'd be simple for them to fix that if they really thought about it, but that's a separate discussion.

    The issue I have is when multiple radiators request low heat, because that does actually fire the boiler but none of the requesters actually get any of the requested heat as they haven't opened enough. More of an issue this year when gas prices are what they are.
  • Hunter
    edited November 2022

    I am also in the situation where hardly any wave 1 triggers get water to my radiators despite triggering the boiler many times. I await a response from Support.

    on the plus side they work better than the hive units.

    The only solution here is to adjust the logic to open the valves more at low demand. Placing shorter extension that make the valve not close leads to a scenario of the valves not closing on demand, which will be rubbish and just like my old hives.

    or abandon wave 1 boiler triggers……currently my system doesn’t respond to them anyway apart from wasting energy and the control has not suffered.

  • Jumping in on this thread as I’m observing the same behaviour! Lots of single 1 bar requests and no demand from the boiler, yet a couple and the boiler kicks in and overshoots. This is using Opentherm connections too, something isn’t quite right. I agree with others, be it that fuel prices weren’t through the roof, I wouldn’t be constantly checking my care and project and smart meter usage!

  • Hunter
    edited November 2022

    was grateful to get an event timeline from Tado for my system for a few hrs that I noticed this behaviour. Basically confirms that every 20 mins I get a boiler start for 4 mins with what are closed valves. Seems the logic is that Tado turns the boiler on for a set period at a set frequency and wind up the valve until it adds heat. These valves need to start at a wider opening point at first boiler activation……..I await a solution. A PID controller is not mean to maintain temps below setpoint and in fact it is not even doing that in reality.

    “10:10 November 11, 2022, the temperature is slowly dropping, target temperature is 21 degrees, room temperature is 20.8 degrees.

    Relay inside the Wireless Receiver is activated for 4 minutes, Smart Radiator Thermostat is opening the valve slightly more. 

    Room temperature is maintained at around 20.84 degrees, so the relay activates again at 10:30 again, it is active for 4 minutes, providing the radiator with enough heat to maintain the temperature.

    Relay is activated at 10:50 again, and again for 4 minutes, maintaining the temperature which is now 28.5 degrees.

    Room started dropping to 20.82 degrees, so the Smart Radiator Thermostat opened the valve slightly more again, and the relay activates again at 11:10 and is active for 6 minutes, but now with the Smart Radiator Thermostat allowing a bit more temperature into the radiators.

    Room temperature successfully increases to 20.92 degrees, but does not overshoot.

    This event repeats itself until 12:50, when the temperature reached 21.2 degrees.”

  • Just had a email from support, they have adjusted the opening of the valves for low heat demands. Not sure from the email if that was for me or everyone but will be testing….

  • @Crash_Evans yeah I agree. It feels like something has broken in the logic of Tado to me. I'm not using OpenTherm and constantly getting huge overshoots of temperature. 0.3 degrees above target temp and boiler still on 100%.

    It would be much better if the logic for this kind of stuff was made open-source so bugs can be found and fixed. Wasting tons of gas at the moment with a house too hot that I didn't ask for.

  • "was grateful to get an event timeline from Tado for my system for a few hrs that I noticed this behaviour. Basically confirms that every 20 mins I get a boiler start for 4 mins"


    I've observed the exact same behaviour with my own system. I can't speak for the closed valves on initial boiler firing. I've certainly suffered the same in the past and complained at the time - around a year ago, maybe. Supposedly they applied some adjustments, but I've never bothered to confirm any improvement in operation. However, if the heating is off overnight I can see a burn time of anything up to a solid 40 minutes to bring things up to temp, but there really doesn't seem to be any sophisticated AI or learning here - it's more just trial and error, four minutes at a time, until it starts working. FWIW my boiler takes 20 seconds from relay click to burner firing, so my system only gets 3:40 heat every twenty minutes when up and running throughout the day. Exceptionally it might run a bit longer, possibly on colder days.

    But, with all that said, I've been a bit creative with my system configuration to avoid closed valve syndrome and to improve boiler/system efficiency....

    Of nine radiators, only one can fire the boiler - the bathroom. Just yesterday I dismounted the SRT from this rad so that when the bathroom needs heat it will absolutely receive heat and not block it. All other rads are independent, with several set to temperatures that are comfortable, but likely to leave the rads often needing a little extra heat and with valves open. So my set temperatures are really temperature limits rather than temperature targets.

    Thus, whenever the boiler is running there are usually a few rads with open valves, the bathroom fully open, so the heat can always circulate, the whole house gets heated instead of an individual room, one at a time (with a closed valve) and the 9 kW minimum output from the boiler can be dispersed more effectively through several rads at once.

    Here's how things are looking right now, with all valves except one open for business.

  • andyblac
    andyblac ✭✭✭
    edited November 2022

    @eezytiger slightly off topic... But whats the Auto-Assist icon you have in the app for... I don't see it in my App, but when i go to Settings "Auto-Assist" it states that "Auto-Assist is included in your tado˚ Starter kit.

    is anyone else missing this or is it just me ????

  • eezytiger
    eezytiger ✭✭✭
    edited November 2022
    @andyblac Auto Assist is a paid for feature to increase automation and provide additional data of questionable worth. I subscribed for my first year with Tado, but have not renewed.
  • andyblac
    andyblac ✭✭✭
    edited November 2022

    @eezytiger I have it FREE as I purchased my tado˚ system back when it was not a subscription service. I.E i get Engergy IQ, GEO Fencing etc..., There is no option for me to subscribe as it already included, yet I don't have that icon

  • Sorry, I cannot edit my previous post to add an image, no idea why. That's Tado community forum for you. Anyway, here's the gist.

  • @eezytiger OK now it makes sense, that is where you subscribe to it, and as is FREE to me, i don't need that part of the App. Thanks.

  • Anyone having this issue, I have reduced my useless boiler ignitions to from several to a one or two via intervention from support. I have fed back that I would like further increased SRV position at low heat demand settings to further ensure that each boiler ignition has a purpose. If you have it support can indeed help.

  • I've just had my minimum burn time increased, effective today. I'll see how it pans out.

    As for valves closed when boiler is lit - still a problem. I'm still experimenting, but the bathroom is the only room that can fire the boiler. Last night I discovered boiler on and no flow through the bathroom rad. This is completely useless. Any time an SRT DEMANDS (not requests) heat, it should be fully open. No sense in any other state.

    So I've dismounted the SRT from the bathroom rad.

    In fact, today, I've gone a step further, as an experiment. I've set all independent rooms to 25C, to keep them fully open throughout the day. When the bathroom needs heating the whole house will be heated - the Heat Geek scenario of maximising emitter volume/area - which will contribute to heating the bathroom from the landing and adjacent bedroom. If any room gets stupidly hot then I can tweak things, but right now I'm simply observing what happens. Some radiator balancing tweaks might be in order, but that remains to be seen.

  • Hunter
    edited November 2022

    @eezytiger Min burn time is that for digital or relay? That would also be an improvement for me on relay. 4 mins is short to spin up your boiler and reach flow temperature. That said lower flow temp being a generated at low heat demands mimics load compensation for relay. Was confused at the difference around demand verses request, is the controller more polite ; )

  • andyblac
    andyblac ✭✭✭
    edited November 2022

    @eezytiger this is why I started a suggestion requesting "call for heat via schedule", so we can set our TRV's to be independent via Schedules, and call for heat when required. WE NEED better control over "CALL FOR HEAT" IMO.

    CALL FOR HEAT should be just that, FIRE THE DAM BOILER wether is it 1 bar or 3, the TRV should be FULLY OPEN, and if using Digital link the "demand" is controlled via the call demand 1,2 or 3 bars.

    Tado needs to stop messing about with the TRV open position, after all the why we have "lockshield valves"