Underfloor heating and solar thermal

Hello and good day,

I would like to inquire about your experiences regarding heat loss. I have 6 tube collectors on my roof facing south. The yield and the system itself are working very well. Now, I have partially turned on the heating for a few days. The flow temperature of the underfloor heating is between 24-28 degrees depending on the outside temperature. I do not consider this to be particularly high. On sunny days, the storage tank (hot water and underfloor heating, 1000 L) is heated up to 60 degrees. When I look at the display in the morning, the storage tank loses over 30 degrees of heat (but not the hot water, of course). What are your experiences? Am I worrying for nothing, and is this completely normal?

Best regards.

PS: I will of course be happy to introduce myself and complete my profile later.

I don't have solar thermal, so I can only say something about the pure flow temperature (VLT) of our heat pump.

I have set a flow temperature of 24° at 20° outside temperature and a slope of 0.2.
That means at 10° outside temperature, the flow temperature should be 26°, at 5° outside temperature 27°, and at 0° outside temperature 28°.
I have disconnected most of the ERR and thus kept the heating circuits continuously open.
However, I am currently testing again. Last year, I had the curve set 1° higher for the entire heating season.

So your 24-28° is nothing out of the ordinary.

Hello Musketeer, thank you very much for the feedback. So the flow temperature. I would also consider it quite normal as a "layman". What irritates me a bit are the 30 degrees of heat loss per night. This causes the following: On a super sunny day like yesterday and today, the system barely manages to heat the temperature to 53 degrees from 3:00 pm... so for the hot water demand. ;-) the next morning again 28 degrees...... is the heat lost somewhere due to a wrong setting or does the underfloor heating really consume that much?

I can only help you to a limited extent with that question. However, I do not believe that heat is lost, and the heating system should actually not turn on at more than 28° VLT. I have no empirical data due to the lack of solar thermal systems.

I suspect that the pump for the underfloor heating may not run or only rarely run during the day, or that most of the heating circuits close the ERR due to solar radiation. When temperatures drop at night, the ERR then perhaps open and all the water is mixed so that a lower average temperature is established.

On sunny days, the storage tank (for hot water and underfloor heating, 1000 L) is heated up to 60 degrees. When I look at the display in the morning, the storage tank loses more than 30 degrees of heat (not the hot water, of course).

The temperature difference of 30° in 1000 L of water corresponds to approximately 35 kWh of energy, which in turn roughly equals 3.5 m³ of natural gas

Best regards

Hello and good morning,
exactly these values fit. At least with regard to solar. For example, the system managed about 30 kWh yesterday and 33.5 the day before. I think this is a good value. Does anyone happen to have comparison values?
My main concern was whether this "loss/consumption" is completely normal or if I should be worried? To be honest, I am currently testing something with the heating to find the appropriate values. Last night, I changed the Temp.-Adjustment value from originally 1.0 to -1.0. Due to this change, the loss dropped to 9.0 degrees (instead of about 30) per night. Let's see how this now affects the room temperature? Best regards