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
Hello,
- What is the actual energy demand for heating and hot water?
- What is the required capacity for each?
- Which climate data are relevant for the location?
Possibly a horizontal ground collector (trench collector) could be an option, which does not require 3 m (10 feet) depth :-)
Best regards.
dimah schrieb:Those are quite helpful, but:
....Details about the house:.....
- What is the actual energy demand for heating and hot water?
- What is the required capacity for each?
- Which climate data are relevant for the location?
dimah schrieb:A bit odd in hindsight! ;-)
....They told us back then that they would try to implement the heating with a deep borehole and probe, but they were not sure if it would work because we are building in an area where drilling permits are very unlikely, as it belongs to the water protection zone of Carolinen Brunnen.
dimah schrieb:Was there no soil survey done for the building project? Do inconsistencies only show up afterwards?
....Now, during the excavation of the basement, they encountered a shale layer at about 3 m (10 feet) deep, and suddenly they say they cannot drill into such a layer ...
Possibly a horizontal ground collector (trench collector) could be an option, which does not require 3 m (10 feet) depth :-)
dimah schrieb:Send that expert to the desert!
....He also said that an air source heat pump is more efficient compared to a ground source heat pump because the unit does not need an electric heating element down to -20°C ( -4°F), and the ground source heat pump would be insufficient in frosty conditions like last year, requiring the electric heating element to kick in, which can cost several hundred euros for two months of continuous frost in winter.
dimah schrieb:Is that for heating only, or does it include hot water as well? How did he arrive at this figure?
....He also calculated for me that with a heat demand of 15,000 (k)Wh per year ...
dimah schrieb:Both figures are way off, if the 15,000 kWh is correct! ;-)
....and assuming an electricity price of around 15 cents/kWh, I would have to pay about 600 € per year for the ground source heat pump and 780 € for the air source heat pump
Best regards.
omlo schrieb:
....the heating engineer refers to 15 kW heating demand, not electrical power.... so the figures are quite plausible. A refrigeration system master technician should actually be able to distinguish between energy and power! 🙁Regards
€uro schrieb:
A certified refrigeration engineer should actually be able to distinguish between energy and power! 🙁
Best regards. I don’t recall mentioning energy.
The text states a heating demand of 15 kW: Quote: "heating demand of 15,000 (k)w"
If this refers to the "annual heating energy demand" (then the unit would be kWh), even better.
And don’t forget: The listed heat pump has a COP of about 4.4.
omlo schrieb:
I don’t recall mentioning energy.
The text states a heat demand of 15 kW: Quote: "Heat demand of 15,000 (k)w" Heat always equals energy (kWh). A layperson might sometimes confuse the two ;-) omlo schrieb:
And don’t forget: The mentioned heat pump has a COP of about 4.4. Which one? Especially for air source heat pumps, individual COP values play only a minor role; what matters for the user is the achievable annual performance factor. That’s where the real difference shows ;-)
Best regards.
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