Is a buffer tank useful in a heat pump?

So you have 170m² of heated area with screed. If you assume 100kg/m², that is 17t of "buffer mass." If you now add 500l, that is about 3% more. Now you could assume that it therefore has the capacity to extend the cycles by 3%. I can't imagine that this brings any benefit. It is more important here to go back to all the settings and also open the valves on the ground floor.

Actually, only a properly large buffer tank for the heating remains as a solution for a messed-up heating design. With a 3kW lower modulation limit for the well-insulated house, the heat pump can’t help but cycle heavily, so you can almost watch it aging to death (keyword compressor starts).

I would actually work with two separate tanks and as soon as the heat pump needs to be replaced, switch to a significantly smaller unit and disconnect the heat pump buffer again.

So you have 170m² heated area with screed. If you assume 100kg/m², that’s 17 tons of "buffer mass". If you now add 500l, that’s about 3% more. Now one could assume that it has the capability to extend the cycles by 3%.

I can’t imagine that this does much good.

More important here is for everyone to check all the settings again and also open the valves on the ground floor.

Hm, these two opinions somehow contradict each other.

More importantly, everyone should check all settings again here and also open the valves in the EG.

But that doesn’t help in autumn or spring when the 3kW minimum output for the house is simply way too high. Just like in the last few days. The heating system can’t get rid of its far too high output at all.

Basically, I agree with you that a heat pump should run without a buffer. But the heat has to go somewhere.

But that doesn't help in autumn or spring when the 3kW minimum power for the house is simply far too high. Just like in the last few days. The heating can't get rid of its far too high output at all.

Basically, I agree with you that a heat pump should run without a buffer. But the heat has to go somewhere.

If a buffer helps, I am happy to install one. RotorMotor says it doesn’t help.

>>>

The heat pump shows the following annual balance:
Heating 12,740 kWh
Cooling 1,850 kWh
Electricity 3,180 kWh
Annual performance factor: 4.6

I am currently querying the data shown by the identical, faultlessly operating heat pump of the neighbors.

But the heat has to go somewhere.

Yes, into the 17t screed.
Of course, you need a few cycles a day, but that's no problem if you use the 17t as a buffer.

If a buffer helps, I'd gladly install it. RotorMotor says it doesn't help.

At least physically, the 3% more mass doesn't bring anything at first.
But it could be that the heat pump is badly configured or can't be configured any better.
And thus, with a buffer as a hydraulic separator and its own mixing module, the cycling is reduced.
However, the efficiency will then suffer significantly because you would/must operate the heat pump with much higher flow temperatures.

But as I said, first focus on the control system.

1) House & heat pump are 7 years old. Heat pump used to make 24 starts per day, now the compressor is broken, I have already discussed all that. One solution option is a buffer tank. Since I don’t want the discussion to get out of hand and I specifically want to learn something about the buffer tank topic, I formulated the request this way.

Or instead of €5,000 compressor replacement, rather a new, better dimensioned heat pump? What would that cost (9,000–13,000 euros plus installation)? What delivery time would we have to expect? (In other words, how long could we not shower?)

Honestly? Put in a heat pump suitable for the house. Your basic situation is that you are driving a worn-out car with a residual value of €6,000. The engine breaks down and you put a new engine into the old car, which also drinks fuel endlessly, instead of buying a brand new car for €9,000. Spend €200 on a proper heating load calculation and have a new heat pump installed for you – brand basically doesn’t matter. Even if the initial investment is more expensive. Heat pumps of that size should cost between €6,000 and 9,000 for the material + installation (but more than taking down, putting aside and reinstalling + screwing on is not necessary).