Our planning is becoming more concrete now, and the architect is obtaining initial quotes for the trades. This includes a quote for the heating system, and I’m unsure how to evaluate it. I have no idea whether the offered system is correctly sized, whether the price is justified, or if there might be a much better alternative.
We definitely want to install an air-to-water heat pump with an outdoor unit. If the budget allows, we would also like to install a photovoltaic system with battery storage right away; if not, this will definitely happen later. I assume this needs to be taken into account when planning the heating system. The house will have a living area of about 155 sqm (1,670 sqft) over two full floors, all underfloor heating, and will be occupied by four people. What else should be considered regarding the heating system?
The first quote is as follows:
Buderus air-to-water heat pump package WLW196i.2-6 AR with heat pump manager for outdoor installation, heating capacity 7.3 kW, immersion heater, 190-liter hot water storage tank, connection accessories, circulation pump, pump group for heating and domestic hot water operation, heating circuit connection set, boiler safety set, cap valve, 120-liter buffer tank, diaphragm expansion vessel, circulation pump, shut-off valve and piping, including 8m (26 ft) of supply line between outdoor and indoor units through builder-installed conduit, heat pump prepared for cooling with humidity sensor and dew point sensor, supply and installation: €19,468.30.
Additionally, of course, all preparations for the underfloor heating, insulation, controls, etc.
This raises a lot of questions for me. Is this a good system? Is the heating capacity properly sized? Is the hot water storage tank correctly sized? Is the buffer tank appropriate? Is the price reasonable? When I search for the same system on Google, I find offers under €12,000, but of course, I don’t know if these include everything listed above and whether such offers are truly comparable.
I would like to better understand what to watch out for and how to proceed. This trade is one of the bigger and more important items, where it’s easy to spend too much or choose the wrong option.
We definitely want to install an air-to-water heat pump with an outdoor unit. If the budget allows, we would also like to install a photovoltaic system with battery storage right away; if not, this will definitely happen later. I assume this needs to be taken into account when planning the heating system. The house will have a living area of about 155 sqm (1,670 sqft) over two full floors, all underfloor heating, and will be occupied by four people. What else should be considered regarding the heating system?
The first quote is as follows:
Buderus air-to-water heat pump package WLW196i.2-6 AR with heat pump manager for outdoor installation, heating capacity 7.3 kW, immersion heater, 190-liter hot water storage tank, connection accessories, circulation pump, pump group for heating and domestic hot water operation, heating circuit connection set, boiler safety set, cap valve, 120-liter buffer tank, diaphragm expansion vessel, circulation pump, shut-off valve and piping, including 8m (26 ft) of supply line between outdoor and indoor units through builder-installed conduit, heat pump prepared for cooling with humidity sensor and dew point sensor, supply and installation: €19,468.30.
Additionally, of course, all preparations for the underfloor heating, insulation, controls, etc.
This raises a lot of questions for me. Is this a good system? Is the heating capacity properly sized? Is the hot water storage tank correctly sized? Is the buffer tank appropriate? Is the price reasonable? When I search for the same system on Google, I find offers under €12,000, but of course, I don’t know if these include everything listed above and whether such offers are truly comparable.
I would like to better understand what to watch out for and how to proceed. This trade is one of the bigger and more important items, where it’s easy to spend too much or choose the wrong option.
W
WilderSueden30 Sep 2023 18:18Karlsson schrieb:
What else should be considered regarding the heating system?The building envelope, for example? It is much more important than the number of occupants. Your 7.3kW is probably slightly oversized. A detailed heat load calculation will give you more precise information. A buffer tank is counterproductive when using a heat pump. Whether 190 liters (50 gallons) of hot water are sufficient depends on your showering and especially bathing habits.R
RotorMotor30 Sep 2023 18:20What results did you get from the (room-by-room) heating load calculation?
If you haven’t done it yet, it definitely makes sense to calculate it before ordering a heating system.
If you haven’t done it yet, it definitely makes sense to calculate it before ordering a heating system.
B
Benutzer 100130 Sep 2023 18:46If you start without a planner, you can still give the heating engineer a few basic specifications.
For example, a maximum flow temperature of 25–28°C (77–82°F) will already rule out about 80% of the poor installers who say, "We’ve always done it this way."
Pipe spacing should never exceed 10cm (4 inches), and in bathrooms, you must run pipes along the walls. The maximum pipe length should be 80m (262 feet).
With 7.5 kW, you can heat a 300m² (3,230 ft²) house in the Swabian Alb region to 25°C (77°F). So this is way too large. It’s better to perform room-by-room heating load calculations based on realistic values. For example, 24°C (75°F) in the bathroom, 22°C (72°F) in living areas, and 20°C (68°F) in bedrooms. You should be able to achieve these temperatures in the bathroom without any additional heating.
For a 150m² (1,615 ft²) house, the heat output usually comes down to around 4 kW. So the modulating range should be between 1.5 and 4 kW.
Regarding the buffer tank, this depends on the bathtub size and how long you shower. We have a 300-liter (79 gallons) tank for four people plus my mother-in-law in the granny flat, and the hot water has never run out—unless I’ve been experimenting with the buffer 🙂
Don’t let the heating engineer tell you it can’t be done. They just want to do the job quickly and comfortably. You’ll pay the price later with your electricity bill, and energy costs won’t get any cheaper.
For example, a maximum flow temperature of 25–28°C (77–82°F) will already rule out about 80% of the poor installers who say, "We’ve always done it this way."
Pipe spacing should never exceed 10cm (4 inches), and in bathrooms, you must run pipes along the walls. The maximum pipe length should be 80m (262 feet).
With 7.5 kW, you can heat a 300m² (3,230 ft²) house in the Swabian Alb region to 25°C (77°F). So this is way too large. It’s better to perform room-by-room heating load calculations based on realistic values. For example, 24°C (75°F) in the bathroom, 22°C (72°F) in living areas, and 20°C (68°F) in bedrooms. You should be able to achieve these temperatures in the bathroom without any additional heating.
For a 150m² (1,615 ft²) house, the heat output usually comes down to around 4 kW. So the modulating range should be between 1.5 and 4 kW.
Regarding the buffer tank, this depends on the bathtub size and how long you shower. We have a 300-liter (79 gallons) tank for four people plus my mother-in-law in the granny flat, and the hot water has never run out—unless I’ve been experimenting with the buffer 🙂
Don’t let the heating engineer tell you it can’t be done. They just want to do the job quickly and comfortably. You’ll pay the price later with your electricity bill, and energy costs won’t get any cheaper.
X
xMisterDx30 Sep 2023 18:55The claim that electricity will not get cheaper is a bold statement that is increasingly heard but is not supported by any evidence.
When heating systems become significantly more expensive due to, in part, unreasonable requirements such as a maximum flow temperature of 25°C (77°F), costing 10,000, 15,000, or even 20,000 EUR (euros) more—when exactly does one recover these additional costs? You have to pay that money upfront, after all...
When heating systems become significantly more expensive due to, in part, unreasonable requirements such as a maximum flow temperature of 25°C (77°F), costing 10,000, 15,000, or even 20,000 EUR (euros) more—when exactly does one recover these additional costs? You have to pay that money upfront, after all...
Thank you very much for the valuable tips. I will now request the heating load calculation. The 7.5 kW also seemed quite high to me, as I have usually seen around 5 kW mentioned for this size in this forum. What is the purpose of this buffer tank, and why is it considered counterproductive with a heat pump?
Similar topics