Hi everyone,
what are the advantages and disadvantages of a single-family house?
Option 1:
Heating: Air-to-water heat pump with underfloor heating
Hot water: Air-to-water heat pump
Option 2:
Heating: Air-to-air heat pump (multi-split)
Hot water: Solar thermal system plus a small gas boiler for extended bad weather
what are the advantages and disadvantages of a single-family house?
Option 1:
Heating: Air-to-water heat pump with underfloor heating
Hot water: Air-to-water heat pump
Option 2:
Heating: Air-to-air heat pump (multi-split)
Hot water: Solar thermal system plus a small gas boiler for extended bad weather
I am currently in a situation where, due to working from home in the attic, I installed a multi-split air conditioning system with 4 indoor units.
The energy label values promise a SCOP of 4.6 and a SEER of around 8-9, although I don’t remember the exact figures right now.
In any case, I used it for heating this winter as well, usually when the outside temperature was above zero.
The system kept freezing up and had to defrost frequently, which led to very poor efficiency.
The energy label values promise a SCOP of 4.6 and a SEER of around 8-9, although I don’t remember the exact figures right now.
In any case, I used it for heating this winter as well, usually when the outside temperature was above zero.
The system kept freezing up and had to defrost frequently, which led to very poor efficiency.
I recalculated and compared it with last year’s consumption. I ended up with a poor coefficient of performance of 2.4 using the heat pump. That’s really bad—how can that be? I have a few pipes running a few meters from the outdoor unit up the facade inside a cable duct. Each pipe is insulated on the outside, but overall the insulation is not very good. The company says this is normal and that you don’t do more; they also say it’s pointless to insulate the pipes further because the refrigerant is converted to gas or liquid at the unit, so further insulation isn’t really necessary. Is that correct? 2.4 really isn’t anything…
At this rate, I might as well just keep heating with gas…
At this rate, I might as well just keep heating with gas…
R
RotorMotor14 Aug 2023 15:06Why not share some numbers? How did you calculate it?
The house was handed over as a turnkey project in summer 2014 with a gas consumption of 1692 kWh due to screed drying.
It is equipped with a gas heating system, as well as domestic hot water preparation using a solar storage tank of 300 liters (79 gallons) plus 2 collectors for hot water.
Gas meter readings converted into kWh (1 m³ = 11.28 kWh)
Summer 2014: 1692 kWh
Summer 2015: 11426 kWh = Consumption 9734
Summer 2016: 19356 kWh = Consumption 7930
Summer 2017: 27636 kWh = Consumption 8280
Summer 2018: 34979 kWh = Consumption 7343
Summer 2019: 41758 kWh = Consumption 6779
Summer 2020: 48300 kWh = Consumption 6542
Summer 2021: 56490 kWh = Consumption 8190
Summer 2022: 63089 kWh = Consumption 6599
Summer 2023: 65875 kWh = Consumption 2786
In summer 2022, an air-to-air heat pump was added.
A Panasonic outdoor unit combined with 4 Panasonic Etherea indoor units.
The outdoor unit has a cooling design load of 6.8 kW (23,200 BTU/h).
Power consumption in heating mode ranges from a minimum of 580 watts to a maximum of 2,680 watts.
Electricity meter readings
Summer 2017: 7123 kWh
Summer 2018: 9023 kWh = Consumption 1900
Summer 2019: 11010 kWh = Consumption 1987
Summer 2020: 13266 kWh = Consumption 2256
Summer 2021: 15721 kWh = Consumption 2455
Summer 2022: 18265 kWh = Consumption 2544
Summer 2023: 22512 kWh = Consumption 4247
The Viessmann heating system controller shows the following for the solar thermal hot water system:
39,247 kWh over solar collectors, period 2014–2023.
The following consumption values come from the heat pump app:
Jul 22: Consumption 21 kWh
Aug 22: Consumption 62 kWh
Sep 22: Consumption 33 kWh
Oct 22: Consumption 90 kWh
Nov 22: Consumption 243 kWh
Dec 22: Consumption 385 kWh
Jan 23: Consumption 197 kWh
Feb 23: Consumption 332 kWh
Mar 23: Consumption 87 kWh
Apr 23: Consumption 189 kWh
May 23: Consumption 45 kWh
Jun 23: Consumption 46 kWh
12-month total: 1,730 kWh
I mainly tried to heat with the heat pump, but switched it off at very low temperatures and activated the gas underfloor heating.
In November and April, solar gains were low and no gas heating was used. Gas consumption for hot water preparation was 115 kWh and 120 kWh respectively.
In December, January, February, and March, the gas heating was on, but I tried to estimate the gas consumption for hot water.
In May, with more sun, it dropped to 70 kWh. In June, 18 kWh of gas was used for hot water, now fully supplied again by the solar collectors.
In summer, gas is basically never used.
I estimate a total gas consumption for hot water of around 1170 kWh from summer 2022 to summer 2023.
This means 1617 kWh gas consumption for heating.
Normally, our total annual gas consumption has been around 6,500 to 8,300 kWh. The winter 2022–2023 was relatively cold, so let’s estimate 7,700 kWh.
7,700 - 1,617 = 6,083 kWh heating load that the heat pump had to cover.
According to the app, the heat pump consumed 1,730 kWh.
This gives a COP value of 6,083 / 1,730 = 3.52.
So, I initially miscalculated, but even though I switched off the heat pump during very cold temperatures, the COP is only 3.52.
It is equipped with a gas heating system, as well as domestic hot water preparation using a solar storage tank of 300 liters (79 gallons) plus 2 collectors for hot water.
Gas meter readings converted into kWh (1 m³ = 11.28 kWh)
Summer 2014: 1692 kWh
Summer 2015: 11426 kWh = Consumption 9734
Summer 2016: 19356 kWh = Consumption 7930
Summer 2017: 27636 kWh = Consumption 8280
Summer 2018: 34979 kWh = Consumption 7343
Summer 2019: 41758 kWh = Consumption 6779
Summer 2020: 48300 kWh = Consumption 6542
Summer 2021: 56490 kWh = Consumption 8190
Summer 2022: 63089 kWh = Consumption 6599
Summer 2023: 65875 kWh = Consumption 2786
In summer 2022, an air-to-air heat pump was added.
A Panasonic outdoor unit combined with 4 Panasonic Etherea indoor units.
The outdoor unit has a cooling design load of 6.8 kW (23,200 BTU/h).
Power consumption in heating mode ranges from a minimum of 580 watts to a maximum of 2,680 watts.
Electricity meter readings
Summer 2017: 7123 kWh
Summer 2018: 9023 kWh = Consumption 1900
Summer 2019: 11010 kWh = Consumption 1987
Summer 2020: 13266 kWh = Consumption 2256
Summer 2021: 15721 kWh = Consumption 2455
Summer 2022: 18265 kWh = Consumption 2544
Summer 2023: 22512 kWh = Consumption 4247
The Viessmann heating system controller shows the following for the solar thermal hot water system:
39,247 kWh over solar collectors, period 2014–2023.
The following consumption values come from the heat pump app:
Jul 22: Consumption 21 kWh
Aug 22: Consumption 62 kWh
Sep 22: Consumption 33 kWh
Oct 22: Consumption 90 kWh
Nov 22: Consumption 243 kWh
Dec 22: Consumption 385 kWh
Jan 23: Consumption 197 kWh
Feb 23: Consumption 332 kWh
Mar 23: Consumption 87 kWh
Apr 23: Consumption 189 kWh
May 23: Consumption 45 kWh
Jun 23: Consumption 46 kWh
12-month total: 1,730 kWh
I mainly tried to heat with the heat pump, but switched it off at very low temperatures and activated the gas underfloor heating.
In November and April, solar gains were low and no gas heating was used. Gas consumption for hot water preparation was 115 kWh and 120 kWh respectively.
In December, January, February, and March, the gas heating was on, but I tried to estimate the gas consumption for hot water.
In May, with more sun, it dropped to 70 kWh. In June, 18 kWh of gas was used for hot water, now fully supplied again by the solar collectors.
In summer, gas is basically never used.
I estimate a total gas consumption for hot water of around 1170 kWh from summer 2022 to summer 2023.
This means 1617 kWh gas consumption for heating.
Normally, our total annual gas consumption has been around 6,500 to 8,300 kWh. The winter 2022–2023 was relatively cold, so let’s estimate 7,700 kWh.
7,700 - 1,617 = 6,083 kWh heating load that the heat pump had to cover.
According to the app, the heat pump consumed 1,730 kWh.
This gives a COP value of 6,083 / 1,730 = 3.52.
So, I initially miscalculated, but even though I switched off the heat pump during very cold temperatures, the COP is only 3.52.
R
RotorMotor14 Aug 2023 16:06Thanks for the information!
I have a few more questions:
Was the solar collector previously also used for heating and now no longer?
How is it ensured that it is not warmer now than before?
Where in your calculations is the cooling taken into account?
Because the gas heating system didn’t cover that before. ;-)
I have a few more questions:
Was the solar collector previously also used for heating and now no longer?
How is it ensured that it is not warmer now than before?
Where in your calculations is the cooling taken into account?
Because the gas heating system didn’t cover that before. ;-)
Was the solar collector previously also used for heating and now no longer?
No, it only provides hot water.
How is it ensured that it is not warmer now than before?
It was actually even colder this winter! We had gas running 24/7 in all rooms.
The heat pump was activated more on demand for each room.
Where in your calculations is the cooling taken into account?
That’s true, that was a mistake on my part. 162 of the 1,730 were for cooling, so 1,568. That results in a COP of 3.88.
No, it only provides hot water.
How is it ensured that it is not warmer now than before?
It was actually even colder this winter! We had gas running 24/7 in all rooms.
The heat pump was activated more on demand for each room.
Where in your calculations is the cooling taken into account?
That’s true, that was a mistake on my part. 162 of the 1,730 were for cooling, so 1,568. That results in a COP of 3.88.
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