tado short cycles my boiler, and it's getting on my goat
Hi folks.
I have a fairly simple system - a single tado thermostat, hooked up to a Grant condensing oil boiler. No rad stats, no multizone, no nothing. This system works great, but tado is doing something wrong.
Example: I've been out all day so the Away temp has dropped to 17C. I come home, tado recognises this and returns the set temp to 21C. Boiler fires, runs for 5-10 minutes, then tado turns it off! I don't understand why tado is turning the boiler off when the termostat temp is now only 17.5C and there's still 3.5C to go.
Example 2: normal day, been home and working from home upstairs. Come downstairs where it's colder, so heating is set to go from 20C to 21C at 4pm. Boiler will run for a little while just before 4pm, then turn off. It'll take it to 4:30pm to get to temp because of this on-off-on-off short cycling.
How can I convince this "smart" thermostat to keep the boiler on until the set temp is reached, rather than running the boiler for 10 minutes, turning it off for 5, back on for 15, off for 10, ad infinitum?
Or do I box the whole thing up and get something different?
Comments
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Is the Tado thermostat located close to a radiator / heat source ?
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No, thermostat is at the opposite end of the hall.
Point is the thermostat is not reading a high temp, it’s just the system seems to want to turn the boiler off for no particular reason I can fathom. I hear the boiler burning, then the relay clicks and off it goes. Heating Light is out on the tado box. 5 mins later it clicks back on, boiler fires, rinse and repeat.
I’ve checked the setting on tado, it’s set for S-plan which I have. My boiler is relay controlled, it does not have any of the variable cycle stuff, it’s as simple as it gets - mains is supplied to the boiler and pump and they both come on until the system water gets to 70c, when the boilers thermostat turns it off.0 -
@ZStationUK I have the similar situation like you encountered but using opentherm/digital control and all i can say,after 6 weeks of discussions with support and trying even to set Tado correctly and stop push my nerves to the limit,i have gave up!!! Dont see the smart in Tado as long as i have similar situations like yours,1.5°C below set point and Tado fire the boiler for short then off and took more then 90 min to reach and close the gap of 1.5°C bettwen set and actual temp. Then again same situation repeating all over! Not to say that boiler pump still operates for nothing when boiler not fired and the noise is very frustrating,did not understand why the boiler pump run with water at 25°C?? Only Tado knows!!
There is something strange and weirdo in the Tado soft or maibe too advanced for the boilers soft,even if my boiler is 2019.
Finally, i gave up with opentherm/digital and i have changed Tado to relay on/off and let my boiler to control via weather compensation software build in(Viessmann) and as long as the boiler is in control and Tado just an EXPENSIVE on/off THERMOSTAT is fine,at least have a use and i can control my heat system via internet.For the next winter i will consider somethings else to buy if Tado dont improves or match better with the boilers soft or functionality. Imagine what a burden if i had bought the TRV's like i was intended!
Maibe you can check if the thermostat is set on correct settings,see the installer menu and be sure u are on RO1( if to your boiler not necessary a different set) and operation is on/off relay,try to speak with support(it is slow,i know!!) and ask them to change the on/off fire cycle period and also time period,they can adjust this. Maibe will work better for you and have some peace of mind!
Good luck!
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@ZStationUK You’re confusing some terminology. Smart thermostats use TPI algorithms to turn boilers on and off, but this is not short cycling. Short cycling is when the boiler heat output exceeds the heat dissipated from the radiators. If the radiators are only giving out 10KW of heat then a large boiler has to periodically shut it self down until the excess heat is removed from the system. This is usually achieved by the pump running for 5 minutes with the burner off. A thermostat cannot force a short cycling boiler to keep running.
With a temperature differential of 4°C I would expect Tado to be using a TPI value of 100%, meaning the boiler is permanently on. I wonder if the on/off cycling you have is down to the boiler and not due to Tado’s algorithms. You can check the TPI percentage in the Care & Protect menu. If the Tado TPI value is inappropriate for the 4°C temperature difference then customer support may be able to tweak the algorithms for you.
Note that most oil boilers do not modulate their output, meaning a 21KW boiler will produce that much heat all the time. This differs to a gas boiler that may modulate its heat output between 5-21KW. So oil boilers short cycling is quite common, regardless of the thermostat technology used for controlling the system.
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Thanks for that. I didn't know the exact terminology, but it's not the boiler "tripping off" due to overtemp. I hoped my explanation of the symptoms would have been clear - it's like going to the doctors, you can only describe what you see/feel.
My issue is tado is just turning the boiler off after 4 minutes. I hear the relay click, the Heat light goes off on the tado box, boiler stops.
The boiler only runs when the pump runs, that's how its wired and plumbed, and that's how every system I've come across here in N. Ireland is done. Power from the timer goes through the thermostat (these two replaced by tado in my case), to the motorised valve. The switched contacts on the motorised valve powers up the burner and the pump. The motorised valve controls the 'direction' of the water, either to the hot water cylinder, or the radiators. There is no option to run the pump alone.
Example noted this morning:
Target temp changes to 21C. Room temp 20.4C. tado calls for heat for just over 4 minutes then stops calling for heat - boiler stops. Radiators have gone from stone cold to a slight warmth at the top upstairs, downstairs are still stone cold. 19 minutes later, Room temp is now 20.2C, target temp is still 21C. tado calls for heat again, runs boiler for 9 minutes then tado stops calling for heat. Rads are now starting to get lukewarm.
As for the TPI value, it's at 100%. Care & Protect says it's been heating for 6 hours 16mins today. It's 13:27, and the boiler has actually been running for about 40 minutes early morning, 20 mins mid morning. I've no clue where it gets 6.25hrs from.
I have been in contact with tado support, and they've changed the minimum run time on the boiler to be 20 minutes, and I'm giving that a go. At least with 20 mins run time, the boiler has a fighting chance to get the radiators heated.
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Based on the times you’ve given for the radiators to get warm it does seem like your system needs extra time to heat the home, and is not the short cycling I referred to. Hopefully the change to the minimum run-time will improve things.
In my opinion the heating runtime is a bit misleading as it does not reflect how long the boiler is actually on for. If the system is running at 10% for 8 hours then 8 hours is reported, the same as if the system was running at 100% for 8 hours.
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I am watching this, I too have an oil boiler now and I thought it was funny the boiler went off and on all the time but I had thought it was the boiler hitting target temperature rather than tado doing it. We had not long moved in to the house and it was my first oil boiler so I was unaware what normal lengths should be.
I am also a bit concerned about if it causes any extra wear and tear on the boiler/pumps with the constant flicking on and off.
One thing I also notice that happens every few months is tado will turn the boiler on and leave it on until I manually reboot everything to try and clear it. It has happened when we have not requested heat/water as well.
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I think I have the same issue too. I've had Tado for ages and it's been mostly fine until recently. It turns the boiler on for a bit and then turns it off. I've also noticed that the status shows 'heating' when it's doing no such thing and the boiler has been off for hours. I have an old non condensing gas boiler. The afternoon schedule change is often totally messed up. It's supposed to be warm by 5pm. The status says it's heating but the boiler isn't on. Then it turns it on for 2 minutes and wastes a load of gas as none of the radiators get warm. Then it waits ages and does it again and then by about 7pm it's the right temperature. Meanwhile 20 minutes on the manual setting would have got it up to temperature so if it had started and ran when it first did the early start it would have been fine. It's not the boiler over heating as there are plenty of radiators with a few that have no valves or are on full as the main thermostat temperature is the right level to get rooms warm and putting it on manual it just gets on with it and gets the job done. Which rather defeats the idea of having a smart thermostat.
Strangely the schedule changes and heating behaviour is fine when the one smart room thermostat is calling for heat. That works perfectly. If the main hall tado is wanting heat it messes it up for some reason.
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I solved the issue. I sent the whole tado kit back to Amazon (well past the return date, thank you Amazon!), and replaced it with a Hive system. Which "Just Works(tm)".
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I am having the same problem on a newly installed tado wireless v3 thermostat and controller. the system is an old gravity fed non-pressurised system with a hot water cylinder and old non-condensing boiler. with the old honeywell thermostat the boiler would run continuously untill it reached temp and then dump excess inti the hot water cylinder. However with the tado, it only runs in 2 minute cycles when getting up to temp, even though the app and controller both say they are "heating" they clearly arent.
It used to take 20-30 mins to get up to 20 degrees from 18, now it takes hours of cycling. this cant be normal? we have normal trvs on all rads - currently set to 4/5 or max - no smart ones or other zones.
Any ideas? do i have to sign up to the monthly subscription to get the stats to fix this?
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Start a forum thread.
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Hello,
I have the same problem with an old non-condensating non-modulating gas boiler. It turns on for 2-3 minutes and then turns off even if the desired temperature is still far from reach.
It keeps doing these on/off short cycles all the time.
Is there any way we can make tado not turn off the boiler until it reached desired temperature?
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This sounds like the boiler stat is cutting out when it reaches the set temperature? Possibly lack of water flow, e.g. due to a faulty pump, bypass or valve. Is this an S-plan or Y-plan? Boiler type ? Do you have TRVs on all rads? Are the rads getting hot? Do you have an external bypass?
Suggest that you get a professional to look at the problem.
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