Boiler doesn't stop after schedule
Hi,
I have recently gone from a Honeywell CM907A to the Tado smart thermostat.
The installation went well as far as I can tell. I had 4 wires, Blue, Red, Yellow and Green/Yellow. Only the Blue and Red looked to have been used, going to A and B on the old thermostat.
As per instructions B (red) went to NO on the new thermostat, and A (blue) to COM.
If I recall correctly green/yellow was screwed into the wall, and yellow was loose and tucked away.
I've been having some issues since it has been installed and set up the scheduling. At 10pm the radiator temperatures are set much lower. However I can still hear the boiler whirring away. It's like the thermostat still requests hot water but not necessarily for radiators, reaching 80+ degrees...
In order to fix it I change the season on the boiler, as soon as it changes off winter the boiler calms down, and I can rotate the season back to winter and it remains dormant. Tado doesn't attempt to get hot water again.
Either there's a setting on my boiler, or the thermostat doesn't correctly tell the boiler to stop, potentially one of those 2 wires? Thankfully I'm often in the same room as the boiler but can be 40+ minutes after the schedule change before I realise and have to cycle the seasons as a bandaid fix.
Any ideas of what I can do?
Comments
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While typing that up I did a test.
I did the Boost Heating to all rooms option. This set the boiler running within 2 seconds. I then resumed the schedule, rooms were all currently much warmer than the target. The boiler went quiet after about 2 minutes. But it did work. It just doesn't seem to do it normally, or at least not all the time for some reason.
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You don't say which boiler you have, but I guess the issue is more about the boiler than about Tado. By the sound of it you have a combi boiler and Tado simply opens or closes a relay to turn the boiler on or off. (If I've misjudged your setup then the rest of my response may not apply.)
But while that's all that Tado can do, your boiler might have other ideas. Taking my own combi boiler as an example, every time the boiler stops burning gas the pump will continue running for a further five minutes to carry residual heat away from the heat exchanger. Only after that five minutes (configurable in boiler settings) will the boiler go quiet. The boiler then goes into anti-cycling mode for a period of minutes (variable and configurable) before it will fire up again. Tado can ask for heat, but the boiler won't start up again until it is good and ready. This is not the problem you describe, but I mention it for completeness.
And, depending on how many rads are "on", how cold it is, how insulated your home is, your boiler's capability to modulate to low output and your setting for the CH water temperature the boiler might shut itself off of it cannot control the heat and would overheat of it did not shut off the gas. If this happens it will go into the five minute pump mode, plus anti-cycling, and only then fire up again once it has cooled enough - assuming Tado still wants more heat.
Further to that, my combi has the option of a "comfort" setting for the hot water. Periodically the boiler will fire up to preheat the water within the boiler for the taps so that there is less delay in getting hot water to the taps. So the boiler might be doing things with the water, independent of Tado and the heating. Once I discovered this feature was enabled I turned it off, with no negative outcome for comfort.
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