Hello everyone,
I have a small problem and would like your opinion.
House details:
Semi-detached house with four occupants
142 m² (1,528 sq ft) living area
335 m² (3,606 sq ft) plot size
140 m² (1,507 sq ft) usable area for ground baskets
Solid clay soil
We hired a construction company to build our semi-detached house. We bought the house with KfW 70 standard, underfloor heating, and a ground source heat pump, for which I pay an additional €15,000.
They initially told us that they would try to install the heating system using a deep borehole and probe, but they weren’t sure if that would work because we are building in an area where drilling permits are most likely not granted, as it is part of the Carolinen Brunnen water protection zone. However, they said using ground baskets would be 100% certain, and those would be installed instead of drilling.
It turned out that drilling is not allowed, so 19 ground baskets with a diameter of 45 cm (18 inches), which the heating installer produces himself, are to be installed at a depth of 6 m (20 ft) with a spacing of 3 m (10 ft).
The air-to-water heat pump was supposed to be:
Viessmann Vitocal 300-G, BWC 6 kW
Now, while excavating the basement, they found a layer of shale stone at about 3 m (10 ft) depth, and suddenly they say they cannot drill into this layer. The heating engineer told me today that he wants to discuss the option of an air-to-water heat pump instead, to see if it might be suitable for us.
He said he would choose the market leader for air-to-water heat pumps, which is:
Mitsubishi Zubadan PUHZ-HRP71VHA2 8.1 kW
Additionally, I would pay €2,000 less for the heating system.
He also explained that the air-to-water heat pump is, compared to the ground source pump, more efficient because it can operate down to –20°C (–4°F) without needing an electric heating element. The ground source heat pump, on the other hand, was not sufficient during freezing temperatures like we had last year, and then the electric heating element has to kick in, which can cost several hundred euros over a two-month frost period in winter.
He also calculated that, with an annual heat demand of 15,000 kWh and an electricity price of about €0.15/kWh, I would pay approximately €600 per year for the ground source heat pump and about €780 for the air-to-water heat pump. Compared to gas heating at around €1,200, this is still a saving.
So much for the background, and now my questions:
Thanks a lot!
dimah
I have a small problem and would like your opinion.
House details:
Semi-detached house with four occupants
142 m² (1,528 sq ft) living area
335 m² (3,606 sq ft) plot size
140 m² (1,507 sq ft) usable area for ground baskets
Solid clay soil
We hired a construction company to build our semi-detached house. We bought the house with KfW 70 standard, underfloor heating, and a ground source heat pump, for which I pay an additional €15,000.
They initially told us that they would try to install the heating system using a deep borehole and probe, but they weren’t sure if that would work because we are building in an area where drilling permits are most likely not granted, as it is part of the Carolinen Brunnen water protection zone. However, they said using ground baskets would be 100% certain, and those would be installed instead of drilling.
It turned out that drilling is not allowed, so 19 ground baskets with a diameter of 45 cm (18 inches), which the heating installer produces himself, are to be installed at a depth of 6 m (20 ft) with a spacing of 3 m (10 ft).
The air-to-water heat pump was supposed to be:
Viessmann Vitocal 300-G, BWC 6 kW
Now, while excavating the basement, they found a layer of shale stone at about 3 m (10 ft) depth, and suddenly they say they cannot drill into this layer. The heating engineer told me today that he wants to discuss the option of an air-to-water heat pump instead, to see if it might be suitable for us.
He said he would choose the market leader for air-to-water heat pumps, which is:
Mitsubishi Zubadan PUHZ-HRP71VHA2 8.1 kW
Additionally, I would pay €2,000 less for the heating system.
He also explained that the air-to-water heat pump is, compared to the ground source pump, more efficient because it can operate down to –20°C (–4°F) without needing an electric heating element. The ground source heat pump, on the other hand, was not sufficient during freezing temperatures like we had last year, and then the electric heating element has to kick in, which can cost several hundred euros over a two-month frost period in winter.
He also calculated that, with an annual heat demand of 15,000 kWh and an electricity price of about €0.15/kWh, I would pay approximately €600 per year for the ground source heat pump and about €780 for the air-to-water heat pump. Compared to gas heating at around €1,200, this is still a saving.
So much for the background, and now my questions:
- Is the cost difference of €600 versus €720 plausible?
- Does anyone know the Mitsubishi air-to-water heat pump and, especially, how is the noise level? The heating installer told me it is not disturbing if the unit is installed outside. I have triple glazing and so on but am not sure if the unit is loud because I have read differing opinions online.
- Is the pump really powerful enough to operate reliably down to –20°C (–4°F) without issues?
- Would you accept the deal with the €2,000 discount, or do you think it’s possible to negotiate a better deal with the company?
Thanks a lot!
dimah
Häuslebauer40 schrieb:
Don’t trench collectors have a significant disadvantage? Could it be that they actually remove heat from the ground, causing conditions similar to Death Valley, where not even the grass grows properly? A trench collector is not a miracle solution either. In fact, errors in source sizing are still made today. If the ground source is designed too conservatively, it can overload the soil, resulting in excessively "cold legs" that negatively affect vegetation. A similar level of effort that is required for evaluating climate and performance data with an air-source heat pump is also necessary for sizing the ground source in a brine heat pump system. Best regards.