ᐅ Replacing a Gas Heating System with a Heat Pump in an Existing Property
Created on: 21 Jul 2022 10:50
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tOkra1984T
tOkra198421 Jul 2022 10:50Hello,
My name is Thomas, and in 2018 we purchased an existing property.
The building was constructed in 1968.
In 2001, the ground floor (partly underground due to the slope) was renovated, and a larger extension was added.
Altogether, the ground floor now has 150m² (1,615 sq ft) of living space. The extension is single-story (flat roof, green roof) and was insulated with PUR foam. Everything was done to a good standard with KNX and so on.
The rest of the old building’s ground floor was also renovated (insulated floor, new wiring, etc.).
New double-glazed windows were installed throughout the entire house. Heating and hot water are currently provided by gas. A photovoltaic system with a capacity of 9.9 kWp is installed.
To summarize:
Ground floor: 150m² (1,615 sq ft) with underfloor heating everywhere except in one child’s room and the bedroom—these rooms have radiators. A split air conditioning system will also be installed.
First floor: about 70m² (750 sq ft), only radiators. A split air conditioning system with a good Coefficient of Performance (COP) will be installed here as well, possibly for heating. This floor is hardly used at the moment.
Second floor: converted attic with about 50m² (540 sq ft), radiators only. This floor is not occupied and likely never will be. It serves as storage space or similar. I am not aiming for absolute comfort temperatures here. The roof is old but insulated with wood fiber.
According to the energy performance certificate at purchase, the building has a final energy demand of 70.2 kWh/m² (22,500 BTU/ft²).
The heat from the ground floor almost suffices to warm the first floor through the ceiling.
As a quick solution to reduce gas consumption, I will soon be installing the two split air conditioning units.
Next year or so, I would like to install a heat pump. I am not really worried that a low flow temperature will be sufficient for the ground floor. On the first floor, the split system would cover peak loads. Yes, I know this is also a heat pump, but the flow temperature of the heating heat pump should be kept as low as possible.
I will be submitting an application this week to BAFA for the split air conditioning unit and the air-to-water heat pump.
Now to my first questions (there may be more over time 🙂 ):
1. My technical room is very small, and when the builder came to inspect it, he immediately said, "Oh dear, we won’t get a buffer tank in here." I have read a lot and some say a buffer tank doesn’t really make sense anyway. So I would prefer to skip the buffer tank. However, is this irrelevant for the BAFA funding, or is it a requirement for the subsidy?
2. In the next meeting with the builder, I want to have concrete ideas ready. As far as I have read, a 300-liter (80-gallon) hot water tank seems reasonable for us (2 adults, 2 children currently).
3. What heating capacity should the air-to-water heat pump roughly deliver in my case?
4. Currently, my gas boiler heats the hot water to 60°C (140°F). Can I safely reduce this to 50°C (122°F) concerning the risk of Legionella?
I am sure more questions will come to mind, but I just wanted to start a thread now—I can add more later.
I appreciate all tips and advice.
My name is Thomas, and in 2018 we purchased an existing property.
The building was constructed in 1968.
In 2001, the ground floor (partly underground due to the slope) was renovated, and a larger extension was added.
Altogether, the ground floor now has 150m² (1,615 sq ft) of living space. The extension is single-story (flat roof, green roof) and was insulated with PUR foam. Everything was done to a good standard with KNX and so on.
The rest of the old building’s ground floor was also renovated (insulated floor, new wiring, etc.).
New double-glazed windows were installed throughout the entire house. Heating and hot water are currently provided by gas. A photovoltaic system with a capacity of 9.9 kWp is installed.
To summarize:
Ground floor: 150m² (1,615 sq ft) with underfloor heating everywhere except in one child’s room and the bedroom—these rooms have radiators. A split air conditioning system will also be installed.
First floor: about 70m² (750 sq ft), only radiators. A split air conditioning system with a good Coefficient of Performance (COP) will be installed here as well, possibly for heating. This floor is hardly used at the moment.
Second floor: converted attic with about 50m² (540 sq ft), radiators only. This floor is not occupied and likely never will be. It serves as storage space or similar. I am not aiming for absolute comfort temperatures here. The roof is old but insulated with wood fiber.
According to the energy performance certificate at purchase, the building has a final energy demand of 70.2 kWh/m² (22,500 BTU/ft²).
The heat from the ground floor almost suffices to warm the first floor through the ceiling.
As a quick solution to reduce gas consumption, I will soon be installing the two split air conditioning units.
Next year or so, I would like to install a heat pump. I am not really worried that a low flow temperature will be sufficient for the ground floor. On the first floor, the split system would cover peak loads. Yes, I know this is also a heat pump, but the flow temperature of the heating heat pump should be kept as low as possible.
I will be submitting an application this week to BAFA for the split air conditioning unit and the air-to-water heat pump.
Now to my first questions (there may be more over time 🙂 ):
1. My technical room is very small, and when the builder came to inspect it, he immediately said, "Oh dear, we won’t get a buffer tank in here." I have read a lot and some say a buffer tank doesn’t really make sense anyway. So I would prefer to skip the buffer tank. However, is this irrelevant for the BAFA funding, or is it a requirement for the subsidy?
2. In the next meeting with the builder, I want to have concrete ideas ready. As far as I have read, a 300-liter (80-gallon) hot water tank seems reasonable for us (2 adults, 2 children currently).
3. What heating capacity should the air-to-water heat pump roughly deliver in my case?
4. Currently, my gas boiler heats the hot water to 60°C (140°F). Can I safely reduce this to 50°C (122°F) concerning the risk of Legionella?
I am sure more questions will come to mind, but I just wanted to start a thread now—I can add more later.
I appreciate all tips and advice.
D
Deliverer21 Jul 2022 19:44tOkra1984 schrieb:
Hello,
I’m Thomas, and in 2018 we bought an existing property.
It was built in 1968.
In 2001, the ground floor (partly underground due to the slope location) was renovated, and a larger extension was added.
The total living area of the ground floor is now 150 m² (1,615 sq ft). The extension is single-story (flat roof, green roof) and insulated with PUR foam. Everything was done to a good standard including KNX system, etc.
The rest of the old ground floor was also renovated (insulated floor, new wiring, etc).
The entire house got new windows with double glazing. Currently, heating and domestic hot water are supplied by gas. A photovoltaic system with 9.9 kWp is installed.
Summary:
Ground floor: 150 m² (1,615 sq ft) with underfloor heating everywhere except one child’s room and the bedroom, where radiators are installed. A split air conditioning system will also be installed.
1st floor: about 70 m² (750 sq ft) with radiators only. A split air conditioner with good COP will be installed here as well, possibly for heating. This floor is barely occupied at the moment.
2nd floor: converted attic with roughly 50 m² (540 sq ft). Radiators only. This floor is unoccupied and likely will remain so. It is used mainly for storage or similar purposes. I am not aiming for a comfortable living temperature here. The roof is old but insulated with wood fiber.
According to the energy certificate at purchase, the building’s final energy demand is 70.2 kWh/m² (6.5 kBtu/sq ft).
The heat from the ground floor is almost enough to warm the 1st floor through the ceiling.
As a quick solution to reduce gas consumption, I will soon get the two split air conditioning units.
Next year or so, I plan to install a heat pump. For the ground floor, I don’t expect any issues with a low heating water temperature. On the 1st floor, the split AC will cover peak loads. Yes, I know this is also a heat pump, but I want to keep the supply temperature of the heating heat pump as low as possible.
I will submit the application this week to BAFA for the split AC units and the air-to-water heat pump.
Now to my first questions (there may be more over time 🙂 ):
1. My technical room is very small, and when the builder came for inspection he immediately said “oh dear, we won’t be able to fit a buffer tank in here.” I’ve read a lot already, and some say that a buffer storage tank makes little sense anyway. So I’m thinking of skipping the buffer tank. Is this acceptable for BAFA funding or is a buffer tank a requirement?
2. At my next meeting with the builder, I want to have concrete ideas. From what I’ve read, a 300-liter (79 gallons) hot water storage tank would be suitable for us (2 adults, 2 kids).
3. What output should the air-to-water heat pump approximately provide in my case?
4. Currently, my gas boiler heats domestic hot water to 60°C (140°F). Can I safely reduce this to 50°C (122°F) without Legionella risk?
I’m sure more questions will come up, but I wanted to start this thread now and can add to it later.
Looking forward to all advice.Regarding 1: The combination of radiators and underfloor heating doesn’t make it easier. In general, operation without a buffer tank can work. If not, a small 50-liter (13 gallons) buffer in the return line fits easily even in the smallest utility room, for example mounted on the wall above the washing machine. It doesn’t affect funding eligibility.
Regarding 2: 300 liters (79 gallons) is a good size. If you rarely or never take baths, 200 liters (53 gallons) will also be sufficient.
Regarding 3: The heat pump should have roughly the heating capacity calculated for the building’s heating load at design outdoor temperature—no more, no much less.
Regarding 4: If the hot water tank is small, there is no Legionella risk in a single-family home. Flow rate is more important than temperature, as the water temperature never reaches everywhere in the pipe network anyway.
Deliverer schrieb:
...
Regarding point 2: 300 liters (79 gallons) works well. If baths are not taken (or only very rarely), 200 liters (53 gallons) are also sufficient.
..
Regarding point 4: If the hot water tank is small, there is no Legionella risk in a single-family home. Flow rate is more important than temperature, since the latter never reaches everywhere in the pipe network anyway.Regarding point 2, I can confirm this from my experience with 2 adults and three children in 2 living units with a 180-liter (47-gallon) combination storage tank integrated in a heat pump—so far we have never had shortages, although there is no bathtub.Regarding point 4, we also had the temperature lowered during commissioning by the factory service technician (who briefly mentioned that we should actually press the button to confirm the parameter for legal reasons but ended up doing it himself).
A split air conditioner is an air-to-air heat pump, so why should it work more efficiently at low temperatures than a conventional air-to-water heat pump?
Regarding legionella, regular temperature increases help, either automatically every few weeks or done manually. However, this is not an issue in single-family homes, but only in large systems where no water is drawn for months at a time.
Regarding legionella, regular temperature increases help, either automatically every few weeks or done manually. However, this is not an issue in single-family homes, but only in large systems where no water is drawn for months at a time.
T
tOkra198422 Jul 2022 09:56Regarding the split air conditioning system:
It is mainly intended for the first floor, where only radiators are installed.
Of course, I want to achieve a low supply temperature with the air-to-water heat pump, which probably won’t be sufficient to heat the first floor. The split air conditioning system can help in case it gets too cold.
About legionella: If I raise the hot water storage temperature to, say, 60°C (140°F) once a month, how much can I lower it for the rest of the time? To 50°C (122°F) or even less?
It is mainly intended for the first floor, where only radiators are installed.
Of course, I want to achieve a low supply temperature with the air-to-water heat pump, which probably won’t be sufficient to heat the first floor. The split air conditioning system can help in case it gets too cold.
About legionella: If I raise the hot water storage temperature to, say, 60°C (140°F) once a month, how much can I lower it for the rest of the time? To 50°C (122°F) or even less?