Experiences with brine heat pump

Cold (preferably dry) air is best for drying.

Hot (dry) air, if your statement is supposed to be universally valid. I don't know the special case of screed drying that well and am not sure which boundary conditions have to be observed.

It should not, it is about [Bautrocknung]. There you get warm (not long) dry air by heating cold dry air, that is better than with cold humid air..

Definitely ask the heating company whether and how the screed heating can be done with the heat pump - and with which settings (e.g. heating rod continuously on, etc.). There is a defined annual extraction capacity. If this is significantly exceeded and the system was, for example, designed exactly (as it should be) or marginally, the probes could potentially be damaged.

cold dry air heats up

Then it is warm, phew, lucky. We agree. The rest is also true: It is cheaper to heat dry air than moist air. And cold air contains less water at the same relative humidity than warm air ... But the higher the temperature of the drying air, the faster the drying. This effect also outweighs the relative humidity of the fresh, not yet warmed drying air significantly.

Then it is warm, phew, lucky. We agree. The rest is also correct: It is cheaper to heat dry air than moist air. And cold air contains less water at the same relative humidity than warm air ... But the higher the temperature of the drying air, the faster the drying. This effect also outweighs the relative humidity of the fresh, not yet warmed drying air.

Well, you also have to change the air because it becomes moist during drying. It's not just about drying, but about possibly removing many 100 liters of water, and air doesn't absorb that much. If you warm cold air, you get particularly dry, warm air; especially because here in Germany when it’s warm, there is almost always quite high relative humidity (even this summer with us usually well above 60%). So for drying, cold autumn-spring weather is actually best here. Because if you warm 8-degree air with 60% humidity to 30 degrees, that’s a very good approx. 17%, then the air can absorb a lot of water.

What I am still interested in are the maintenance costs... How high are they? How often does maintenance have to be carried out?

In another thread, something was read about 250 EUR/year. I can't imagine what is supposed to be maintained for 250 EUR. The heating engineers always argue with "almost" no maintenance costs?!