Hello everyone,
some background on my questions:
I am currently exploring the possibility of converting our house from a gas heating system to a heat pump. It might sound completely crazy for a house that is just under 7 years old, but this could be funded and financed as an “energy renovation project” together with a photovoltaic system through KFW 261. That could actually make it economically very attractive.
I am still in the evaluation phase and have started initial discussions with heating and solar experts.
This immediately raised some questions for me, because the first offers are quite contradictory to the principles I often see discussed here in the forum:
The insulation level of the house is about KFW 55 standard; however, the overall standard was not met back then due to the gas heating system. The heating demand is around 12,000-13,000 kWh for a total of 270 square meters (2,900 square feet). There is underfloor heating throughout, including the basement.
Best regards,
Andreas
some background on my questions:
I am currently exploring the possibility of converting our house from a gas heating system to a heat pump. It might sound completely crazy for a house that is just under 7 years old, but this could be funded and financed as an “energy renovation project” together with a photovoltaic system through KFW 261. That could actually make it economically very attractive.
I am still in the evaluation phase and have started initial discussions with heating and solar experts.
This immediately raised some questions for me, because the first offers are quite contradictory to the principles I often see discussed here in the forum:
- Buffer tank (heating water) – Question: What exactly is the purpose of this and when does it make sense? So far, no seller has been able to clearly answer this, although the technical answer is simple: it should act as a hysteresis to reduce short cycling of the heat pump. The general idea is understandable, but I don’t really see how 100 liters (35 gallons) of buffer tank help when just the volume of my underfloor heating system already exceeds 200 liters (70 gallons), plus the large mass of screed acting as thermal storage. The current gas heating system works fine without a heating buffer tank.
- Heat pump capacity and modulation – the first quotes naturally come with absurdly oversized heat pumps because they only consider the total heated area of 270 square meters (2,900 square feet). When I point out that 12 or even 16 kW seems excessive, the answer is always: “It can modulate down from 3 to 12 kW.” That’s fine, but exactly this modulation is often warned against. So question: why is modulating down performance considered a problem? Is this the short cycling that people warn about? Technically, modulation means the entire system, including the compressor and all components, runs slower. But then the question arises how efficient it still is.
The insulation level of the house is about KFW 55 standard; however, the overall standard was not met back then due to the gas heating system. The heating demand is around 12,000-13,000 kWh for a total of 270 square meters (2,900 square feet). There is underfloor heating throughout, including the basement.
Best regards,
Andreas
R
RotorMotor5 Nov 2023 10:35Such "tricks" should only be done with fresh water tanks/stations due to the risk of legionella.
D
Daniel-Sp5 Nov 2023 10:36If the storage is emptied daily, there are no problems.
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RotorMotor5 Nov 2023 10:51Daniel-Sp schrieb:
If the storage tank empties daily, there are no problems.With 300 liters (80 gallons), this is not always guaranteed. There are always days when consumption is higher or lower.
More importantly, it cannot be verified whether the tank has truly "emptied."
In any case, the tanks never fully empty. Water always flows in immediately and mixes with the existing Legionella bacteria.
RotorMotor schrieb:
This cannot always be guaranteed with a 300-liter (80-gallon) tank. There are days when consumption is higher or lower.
More importantly, it cannot be verified whether the tank has actually been fully drained.
In any case, the tanks never truly empty. Water constantly flows in and mixes with the existing legionella bacteria. What would be your recommendation then?
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WilderSueden5 Nov 2023 19:43It would be helpful if you could share some information about your water consumption. The three of us easily manage with our 180 liters (48 gallons). I grew up in a family of five with a similarly sized water heater. That worked fine, as long as no one was bathing and showering at the same time.
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