What flow temperatures are you currently running?

Alright, so in simple words, no observation over longer periods. The well-known saying also applies here: "Pics or it didn't happen" Only in this case it must be: "Graphs or it didn't happen".

Has anyone of you ever observed the behavior of the systems and the associated temperatures in the rooms over a longer period of time? These snapshots don’t say anything at all. The flow temperature is constantly going up and down. That means it can have completely different values in the same house at the same outdoor and indoor temperatures.

Freely after Klaus Kinski. "I don’t understand the question." :D
Flow temperature is always up and down.

... The supply temperature is constantly going up and down. That means it can have completely different values in the same house at the same outside temperatures and the same inside temperatures.

what kind of control is that?

Although the flow rate (and thus the heating power) can vary
- depending on the number of rooms currently being heated -
with constant outside and inside temperatures, the supply temperature will usually be constant,
or it will be regulated to the target temperature as long as the current heating power is sufficient.

If the heat pump is return-controlled, then not at all. The supply temperature then depends on several factors. For example, current heating output/compressor frequency, volume flow, difference between return flow and return flow setpoint, heat transmission of the house. From this results the spread and thus the supply temperature. This applies to all Novelan, AIT, and I believe also Nibe. With these heat pumps, the control variable return flow setpoint is better suited for comparison.

The supply temperature is always up and down. For this reason, the meaning of the whole thread doesn't really make sense to me.

but with a constant outside and inside temperature, the supply temperature will generally be constant,

No, it is not, because it depends on what is currently happening in the house and also what has been going on in the last few hours. In addition, neither the inside nor the outside temperature is ever constant and they constantly fluctuate. A house is also not a laboratory object but is generally inhabited.

Indeed, flow temperature is always up and down. For that reason, I don’t really understand the point of the whole thread. No, it isn’t {flow temperature} because it depends on what is currently happening in the house and also what happened in the last few hours. Additionally, neither the indoor nor the outdoor temperature is ever constant and they constantly fluctuate.

I’m not sure if we’re talking about the same thing: Of course, the flow temperature oscillates with the hysteresis of the heat pump compressor around the target temperature. But this is generally constant depending on the slope and level of the control in relation to the outdoor temperature and indoor temperature. Today as well as tomorrow. Regardless, the flow rate of the heating water and thus the radiator temperature fluctuates. (Flow temperature and radiator temperature are NOT identical!) It may be that the control "remembers" the usage type of the rooms and "steps on the gas" upon activation to reach the target temperature faster. But these are all transient states. On average, in the steady state, the flow temperature will be constant depending on the outdoor temperature and settings.