What flow temperatures are you currently running?

Buy an IR thermometer and check the spread on each circuit. What I realized from this is that the HTHK, which was demonized as a short circuit, had a spread of 5k. That’s why it runs at maximum flow in my bathroom. Only then do I reach 23°C. You have to tinker with the UWP for a very long time before you get a perfect result. By perfect, I actually mean damage control of the underfloor heating installed by the heating engineer :p

Currently, AT is just hovering around the heating limit - at least for new buildings during the day - so an adjustment/optimization of the underfloor heating/heat pump is almost excluded. The suitable time/temperature for this will still come…

Base point/desired temperature is at 21°C if both are the same.

At least with Stiebel Eltron, this is not the same. While the base point only shifts the heating curve on the Y axis (1K change base point = 1K change heating curve setpoint), the desired temperature changes the setpoint disproportionately.

But in any case, I would initially experiment with the two parameters (above 0°C, I believe).
Otherwise, in winter, you will just keep increasing the slope again.

So the desired temperature is apparently a parallel shift with Vaillant, meaning the entire heating curve is raised. I haven’t figured out a way to increase the base point yet.

That is also my understanding of the desired temperature at Vaillant and is also described somewhere in the installation manual or user manual.

Although both documents are a huge disgrace in their vague description of the relationships.

However, there are the menu items minimum/maximum heating circuit temperature.

I haven't tried it yet, but if the Vaillant heating curve is based on 20°C flow temperature at 20°C outside temperature, wouldn't the specification for minimum heating circuit temperature, e.g. 22°C, be basically a floor point increase of 2°C? Although I rather suspect that it simply adds 2°C to the target flow temperature in general, according to how I have come to know the Vaillant controller so far.