ᐅ Ground Source Heat Pump – What to Watch for When Reviewing a Quote (Single-Family Home, New Build, KfW 70 Standard)

Hello everyone,

We are planning to build with a general contractor (single-family house, about 136 sqm (1463 sq ft), gable roof, ≤KFW70) and would like to enter the final negotiations with the last 2 or 3 points.

The construction descriptions each list ground source heat pumps (brand name + buffer tank), but without much detail. I would like to ask for your recommendations in this area.

Since brand names probably shouldn’t be mentioned here:
A brine-to-water ground source heat pump with a COP of 4.7 is specified (integrated domestic hot water tank of 185L (49 gallons)). Additionally, a buffer tank, probably between 200 - 300L (53 - 79 gallons), is planned.

1. Is this combination reasonable?
2. What should generally be considered with heat pumps? I definitely want to install a heat meter and a separate electricity meter. What else should be taken into account?
3. Which combination do you consider the most practical (e.g., size of the buffer tank, etc.) for a household of two people (both working, possibly one child in a few years)?

Thank you very much in advance,
Lacos

First of all, the question is how high the heating demand is and whether it can reasonably be covered by a heat pump...

If not, you will be building a money pit... even though the glossy brochures promise a lot, not everything is as it seems...

I would question the usefulness of a buffer tank. Otherwise, I am convinced of brine heat pumps, as they are likely to be a sensible investment given rising energy costs.

With a heat pump, I would rather use two separate tanks... one for domestic hot water and one for heating... otherwise, it runs continuously at full capacity...

Why should it be running at full capacity all the time? Only if it was incorrectly sized...

My ground-source heat pump is currently still operated purely electrically with a 9kW (12 hp) heating element to drive out the residual moisture from the screed. With the 9kW (12 hp) heating cartridge, we manage room temperatures over 30°C (86°F). If it runs at full capacity during normal use, something was planned wrong.

Quote from another forum: ...no matter how you do it later, make sure the domestic hot water tank is separate from the heating storage tank. I made a big mistake with this because in the stratified storage tank, the different temperature layers kept mixing, causing the heat pump to always operate at a high performance level. Only since I properly separated the tanks has everything been stable.