Repair the heat pump for €5,000-7,500 or replace it with a new heat pump?

I seriously wonder what is meant by that for this price.

I don't know how it is with Viessmann, with Nibe an additional heat exchanger and a few 3-way valves are needed. But I was offered that for 4k in 2022. According to the installer, a dew point sensor is not necessary

There is news:

1) A neighbor with the same heating system and bypass valve has the same problem with far too many cycles.

2) A neighbor with the same heating system, without a bypass valve, but with a hydraulic separator, does not have the problem with the cycles, but has the problem that he generated 2.7 times as many kW of heat per year.

This leads me to the following conclusions:

1) The installing company had no clue and messed up in three households.

2) The problem with the two heating systems with bypass valve is probably a bypass valve that is opened too far.

The plan is now as follows:

1) Next Monday, the German sales department of Ecoforest will come and replace the compressor.

2) Afterwards, they will check the bypass valve. Ideally, they will find that it was completely misadjusted. In any case, it should be turned as far as possible to the closed position. (If overpressure problems occur again, it can be opened a bit again.)

3) In the following weeks, I will do a thermal balancing in the house myself. I have a neighbor who will show me how to adjust the flow valves. Then everything will be set so that the valves are as open as possible, but adjusted so that the same temperature of 22.5° is reached in every room. Then in the future, all room thermostats can remain fully open permanently.

4) If there are still many cycles, I still have the following measures in reserve for further optimization:
a) reducing the capacity from 3-12 kW to 3-6 kW or 3-9 kW for heating and/or hot water
b) increasing the differential temperature from 5° to 8° (or 10°)
c) lowering the heating limit to up to 12°
d) increasing the pool heating time from 15 minutes per hour to 30 minutes per hour

A buffer tank will not be installed in the house, or only if none of this helps.

What do you think about it?

Oh dear, it gets even more complicated:

Both neighbors do not have an overflow valve like I do, but a hydraulic separator.

It remains puzzling to me how such different results can occur with the same construction:

Neighbor 1:
- few starts
- excessively high amount of generated heat (factor 2.7)

Neighbor 2:
- excessively high number of starts (factor 5)
- low amount of generated heat

There is nothing to say like this. More information about the houses is needed to be able to estimate whether the 2.7 times consumption is realistic.

We now have an offer for a Daikin Geo 0.85-9.1 kW with 180 liters of hot water and a 300-liter buffer tank for €21,500, with a 35% subsidy the price remains €14,000.

Alternatively, compressor replacement for €4,800.

I might also ask if it’s possible to remove the buffer tank (possibly retrofit it later) and go with the Daikin Geo 0.85-7.5 kW, then the price would decrease.

We now have an offer for a Daikin Geo 0.85-9.1 kW with 180 liters of hot water and 300 liters of buffer storage for €21,500, with 35% funding it remains €14,000. Alternatively, replacement of the compressor for €4,800. Maybe I can still ask if it is possible to remove the buffer storage (possibly retrofitting) and go for the Daikin Geo 0.85-7.5 kW, then the price would decrease.

I don't think the offer is bad at all... The 180 liters should be integrated. Whatever. I would also remove the buffer and choose the smaller variant (even if both have the same modulation limit of 0.85 kW).