Circulation pump capacity and overflow valve

Hmm, there’s just nothing more to say about that old pump that sits in the indoor unit. And no matter what I set, it’s only the above-mentioned liter numbers. What puzzles me is that the pump then only runs at around 60% of its capacity. In hot water mode, it pushes about 1100 liters around.

Merry Christmas to everyone. Can you tell if the heat pump control even demands the full power from the circulation pump? Does the heat pump heat directly into the heating circuit and switch for hot water using a three-way valve? What kind of heat pump do you have, does it modulate its power?

Air-water heat pump Vaillant Arotherm-Split with indoor unit 3.5 kW heating capacity, the system runs directly into the underfloor heating but has the mentioned bypass valve installed and an 18-liter inline buffer tank. Connected is the heating circuit distributor (14 heating circuits) with 28 mm copper pipe laying distance everywhere VA 10. ERR not functioning or disconnected.

Modulating?
What pipe size do the heating coils have?

Yes, the air-to-water heat pump modulates, the heating circuits have been installed with 16mm PEX pipes.
Calculated heating load is 3.2 kW at -12°C and the underfloor heating is designed for 30°C flow and 25°C return. Of the 3.2 kW, approximately 750 watts are ventilation losses, and the controlled residential ventilation was not considered in the 750. Therefore, the actual heating load should only be 2.8 kW if a heat recovery efficiency of 50% is taken into account for the controlled residential ventilation.

With what "percentage" power is the HUP controlled by the heat pump? Can you manually control it at 100%? My heat pump also regulates the power of the HUP to achieve the optimal temperature difference for the best efficiency at the current heating output. Usually, it only demands 600 l/h, at the beginning of the heating cycle with higher power then about 900-1000 l/h. At 100% HUP power I would be at 1800 l/h. However, I calculated 1200 l/h with NAT. installed 17mm pipe. I do not know the control of the Vaillant, but I can imagine that here too the HUP power is adjusted to the current heating output.