What flow temperatures are you currently running?

You definitely need to take action. Before optimizing heating costs anywhere, you first need to get the cycling under control. Falling temperatures have nothing to do with it. The hysteresis is far too low and/or the system is messed up, for example by a buffer, bypass valve.

Do you know what caused the high power consumption starting at around 04:45 AM?


From the net, a "specialized" forum. And yes, assuming the compressor as an "irreplaceable" part or total loss if that thing breaks down, such a system has this kind of lifespan.

Today I will probably get between 25-30 starts at 9-14°C AT.

A little was already clear beforehand that the heat pump is oversized.

Let's see if I raise the energy integral even further.

At what value are you currently?

From the net, a "specialist" forum. And yes, assuming the compressor as an "irreplaceable" part or total loss if that thing breaks down, such a system has such a lifespan.

So rather a random estimate than a verified value from test series.
Are there even any results for the current series with the currently used refrigerant?
Such a compressor seems to cost 1000€.
Very annoying but not irreplaceable.

I still agree with you that it's better to reduce cycling first and then look at efficiency again.

A bit was already clear beforehand that the heat pump is oversized. Which value are you at then? So rather a random estimate than a verified value from test series. Are there even results for the current series with the currently used refrigerant? Such a compressor seems to cost 1000€. Very annoying but not irreplaceable. I’m still with you that it’s better to reduce cycling first and then look at efficiency again.

An oversized heat pump leads to short cycles. However, if the underlying underfloor heating is reasonably well adjusted, it should not per se cause a “short circuit” that would cause the return flow to spike, thus falsely ending the cycle too early and then turning on again shortly after a drop in return flow. In my opinion, this effect is greatly overrated, or it is more likely that the heat pump simply has trouble getting rid of the heat it produces. These are rather botched installations, e.g., with buffer tanks or bypass valves. In the simplest case, the ERR are closed so that no heat is taken off. Blabla random estimate. These are transported empirical values that, by the way, do not apply exclusively to heat pumps. But feel free to present your studies, good luck. Then maybe you’ll also understand why your cost estimate is “a bit” off ;-). A broken compressor is a total loss. Why, someone else can tell you.

Blabla arbitrary estimated value. These are transported experiential values, which by the way do not apply exclusively to heat pumps. But go ahead and set up your studies, good luck. Then perhaps you’ll also understand why your cost estimate is "a bit" off ;-) A broken compressor is a total loss. Why, someone else can tell you.

Why so unobjective? I think it is right and important to critically question not only the manufacturers but also any statements posted in forums. Besides, "experiences from a forum" contradict your statement "in theory." The entries with "100,000 and even after 120,000 no problems yet" are easy to find. But maybe the systems simply haven't existed long enough to be sure that perhaps even 200,000 is not a problem?! Or rather laboratory tests from the manufacturer/test institutes. One manufacturer, for example, names a total runtime of 40,000 hours as the expected service life. Another manufacturer of compressors specifies a design for 150,000 starts. In that case, 20 starts during the transition period would be no problem. When it gets really cold, the heat pump will get rid of its energy then and run longer. Regarding the Vaillant with the refrigerant, however, I can’t find anything concrete.

I become unreasonable when users in forums want information handed to them on a silver platter that they could easily find out themselves (you managed that now) and then complain that it’s not good enough quality. Then do it yourself or pay someone. This is a user forum.

Which ones do you need/would you like? I think since with heating curve 0.16 only 3 cycles in 24h occur, I think it is already well set. Changing from 0.16 to 0.1 changed the temperature in the house by 0.1 degrees

You came from heating curve 0.3… and now even 0.1 is sufficient. 0.3 with room setpoint 20 degrees probably results in the same flow temperatures at 5-10 degrees outdoor temperature as 0.1/22. It gets interesting at temperatures below 0 degrees. You keep fiddling with the volume flows constantly as well. I have been running 0.15/22 in my 130 sqm semi-detached KfW60 house (with an unheated utility basement underneath) for years. Without solar gains, the room temperatures are usually at 22.5. 17 heating circuits: bathroom 2.5 l/min, the rest 1-1.8 l/min. Bedroom 0.5. Volume flow switch 63/2. Heat load calculation 5.9 kW.