Improvements required to Tado heating logic in relay mode.
Hello again all!
As users of Tado in a relay setup (no OpenTherm/no external modulation) will be acutely aware, Tado's default heating logic suffers from severe short cycling issues where Tado will fire the boiler for only a couple of minutes at a time in short succession, behaviour that has brought many of us here to these forums. Some have even had heating engineers tell them this short cycling was causing damage to their boilers. However after using the system for even a short time it is clear that there are further deficiencies that cause similar problems.
Currently Tado devices are not aware of any of other devices in the system and Tado devices are not aware of their own schedules. It has also become clear to me that Tado devices are not aware of changes to the parameters that govern their behaviour and don't take modified values into consideration. This creates silly scenarios like the following:
- 1 Thermostat will turn the boiler off, only for another device to immediately turn it back on again. If you have lots of STRVs that can call for heat your boiler might just never turn off as it bounces around to each device in turn, wasting fuel.
- A Tado device will turn the boiler on, seconds before a change in the schedule that will then turn the boiler off again.
- A Tado device will turn the boiler off, seconds before a change in the schedule that will turn the boiler on again.
The last point is what happened to me this morning: Tado turned on the boiler for 10 minutes, turned it off 30 seconds before the schedule changed and it tried to turn it on again (and couldn't because the boiler said no that's a short cycle - go away).
Along with the severe short cycling this behaviour is illogical, frustrating, damaging to heating appliances, and not befitting a "smart" device and makes Tado feel more like a basic connected device that doesn't have anything more than simple rules governing its operation.
The heating logic needs to be improved to finally fix the short cycling behaviour, make Tado devices aware of what is happening within its own ecosystem and programmed to behave in a more sensible way. It is very surprising to me that these scenarios were not considered when developing Tado's heating algorithm as it becomes evident that this will be a problem within a few weeks of using the system. It makes me wonder if Tado is using some off the shelf PID algorithm that wasn't further developed.
Good heating logic is the most fundamental function of a thermostat. If Tado cannot heat our homes in a sensible fashion that doesn't damage the thing doing the heating then I don't see how adding further features can take priority. My other ongoing suggestion of exposing advanced parameters to users can help us with the short cycling behaviour and more but will not prevent Tado from switching the boiler on and off in an illogical way with different devices or schedule changes. A smart thermostat system should NOT damage your heating appliance!
Comments
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Totally support this.
Tado should consider looking into this and not hide behind a generic response from the support team stating that "all features operate as normal and additional safety measures are in place to prevent excessive boiler wear and tear".
As other users have observed, quite often Tado will do its own thing which is contradicting and doesn't make sense, despite support telling them that it all works fine and as intended.3 -
A smart system is to save money not running the boiler on and off to switch back on for another room burning extra gas when it could have heated the second room at the same time whilst the boiler was running the first time. Get smart Tado and get this implemented.3
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My solution.…
- Request Tado to set a minimum burn time of 10 minutes.
- Ensure that the flow temperature is set appropriately to avoid thermal shutdown. Mine is set to 55C and will shut down once it's reached 57C. Most of the time my boiler will not reach these limits.
- Consider range rating your boiler output so that it only provides the heat required for your property and heat loss characteristics, rather than going full blast every time the boiler fires. I've set my boiler to the minimum output of 9 kW. It's still more than necessary, but way better than the 24 kW maximum that is the default setting.
- VERY IMPORTANT : Make as many rooms as possible "independent" meaning that those rooms cannot fire the boiler. They can have heating schedules set up as desired, but will only be able heat when the boiler has been turned on by another room. Choose wisely and this can be very effective.
For example, in my home I've been running my nine radiators and eight SRTs with only one SRT allowed to fire the boiler - the kitchen, which has 2.3 external walls and a partially exposed roof, plus two air bricks, and it's the coldest room in the house. All other rooms are set to "independent". By keeping the kitchen "warm enough" all the other rooms should also be kept "warm enough" without, themselves, forcing the boiler to fire. The temperature settings for the independent rooms become max temperature limits rather than temperature targets that must be met. This avoids needlessly overheating any of the rooms, although it's possible they won't all heat to the max limit all the time, for example during a big cooking session in the kitchen, which reduces boiler on time. If that's an issue then I can temporarily tweak something (raise the kitchen target temp) just to add a bit more warmth to the house.
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Just to add, here's an example of the firing pattern and flow temps for my boiler between midnight last night and 11:00 this morning. The boiler has fired 20 times in 11 hours, so about twice per hour, and it's only cycled this way because it is too powerful and cannot modulate to a sufficiently low output. It's not Tado's fault.
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I appreciate your inputs @eezytiger! I've also set my minimum firing time to 10 minutes (and minimum 20 off) which does solve most of the short cycling nonsense - however it should still be fixed at the source rather than this patch method, especially if they are not going to give us access to these parameters ourselves. I've also always had my only STRV to accept heat only, but that's because this setup works for me. Lots of people maybe can't or don't want to do that and still want a sensibly functioning heating system.
But this cannot help the problem that Tado devices pay no attention to what any of the other Tado devices are doing, or that it has no awareness of its own schedule. Personally I think this is poor from a system design perspective as in my mind these problems are incredibly obvious when you test the system in a normal fashion. Which makes me think either Tado was not correctly tested on relay systems or they are using some off the shelf packaged algorithm they didn't or couldn't develop further. Or they simply thought this was good enough and would just peddle the absolutely insane "tado° prevents your heating system from switching on and off too often, helping to protect your boiler" line that obviously isn't true at all 🤷♂️
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