Strong fluctuations in temperature

frederikmennes

I am using tado in combination with an Elco Straton boiler. The temperature in the rooms shows very strong fluctuations, and deviates from the temperature set in tado. This is the case in all rooms.

In the graph below, the set temperature is 19 degrees, but the temperature fluctuates between about 16 degrees and 20 degrees. It seems like the heater only works when the temperature has dropped sharply, then works for a while, and then turns off again until the temperature has dropped sharply again.

Does anyone have an idea what could be the cause of this?

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frederikmennes

Thanks for your feedback. However tado has been in use already for several years. I suppose it should have learnt the characteristics already?

johnnyp78

There might be an issue with your boiler if this has started happening recently.

frederikmennes

It’s actually been like this for a while. I believe the tado system was not properly set up by the original owner.

pcone

Looks to me like it's not triggering the boiler (perhaps this room is set to 'independent', and thus whilst it will open the valve, it's not actually pumping hot water through the radiator).

You can see from the graph that the valve is fully open (the darkest grey colour) but the temperature still falling rapidly for a couple of hours, before then suddenly rising. I suspect it only heats when another room requests heat. Does the radiator get hot when the temperature is falling?

wateroakley

I’d agree with the analysis from pcone. The graph looks like an ‘independent’ room setting with a different room/device ‘calling for heat’, four times a day, for about one hour, around 4 am, 10 am, 4 pm and 11 pm? Start by looking at the room settings.

pcone

@frederikmennes : Out of interest, are the spikes in temperature at the same time every day? Also, are they at the same time in every room?

Does the boiler have any other controls (like an old timer, old thermostat) or is it just controlled by Tado?

frederikmennes

Thanks @pcone and @wateroakley for your feedback. Answering your questions:

• The radiator does not generally get hot when the temperature is falling.
• The room is not set to "independent".
• The spikes in temperature were quite consistent during the past weeks.
• To my knowledge the boiler is only controlled by tado.

I would like to add that the temperature fluctuation was completely gone today (see today's graph below: the temperature is consistently around 19 degrees; there is an increase around 8 PM but that was intended).

The outside temperature today was lower than in recent weeks. The outside temperature today was about 0 degrees, while it was about 10 degrees in the past few days. It was also colder in early December, and then the temperature fluctuations were also gone.

Could it be that there is a wrong setting somewhere that causes the heater not to work properly at higher outdoor temperatures?

pcone

I suspect there some setting on the boiler itself then. Does it have an external temperature sensor?

frederikmennes

@pcone yes, the Elco Straton uses an external temperature sensor, namely the Siemens QAC 34 (see here).

johnnyp78

So you’re using weather compensation and Tado? Sounds like you need to tweak the weather compensation curve (or just remove Tado and use that).

frederikmennes

@johnnyp78 Thanks for your feedback. Do you mean I should remove tado entirely, or can I also just disable the weather compensation functionality of tado?

johnnyp78

The weather compensation is nothing to do with Tado. You have an external sensor installed. Your boiler is responding to that. If it were me I would pick one or the other but you may prefer to keep both.

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