ᐅ Operating Costs of Air-to-Water Heat Pumps: Consumption and Defrosting
Created on: 19 Jan 2024 19:39
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Sven2617
Hello everyone,
For four days now, the heat pump (air-to-water, KfW55 standard) in our new building has finally been running, and during this time we have noticed that it
a) consumes around 70 kWh of electricity per day,
b) defrosts about 30 times during the day, roughly every 40 minutes (sensor-controlled, and the fins are constantly white), and
c) is continuously very loud.
Currently, there is no hot water consumption as the house is neither occupied nor are the sanitary installations finished. Only the heating is running. Does anyone have an idea what might be causing this and what can be done about it?
From what I read yesterday, defrosting should only occur every few hours, and the heat pump was sold to us with an estimated annual operating cost of about €700. With the current consumption, that would be reached in one month...
For four days now, the heat pump (air-to-water, KfW55 standard) in our new building has finally been running, and during this time we have noticed that it
a) consumes around 70 kWh of electricity per day,
b) defrosts about 30 times during the day, roughly every 40 minutes (sensor-controlled, and the fins are constantly white), and
c) is continuously very loud.
Currently, there is no hot water consumption as the house is neither occupied nor are the sanitary installations finished. Only the heating is running. Does anyone have an idea what might be causing this and what can be done about it?
From what I read yesterday, defrosting should only occur every few hours, and the heat pump was sold to us with an estimated annual operating cost of about €700. With the current consumption, that would be reached in one month...
J
Jesse Custer20 Jan 2024 05:16My thoughts:
- The thawing process has also been a disaster for us since Tuesday, but that is due to physics and the specific weather conditions.
- The building was probably completely cooled down, so the high initial consumption is normal.
- We obviously cannot assess any other factors, such as if there are additional elements in the house or how the system is configured, etc.
In general, the last four days have also been the highest consumption period for us since installation...
- The thawing process has also been a disaster for us since Tuesday, but that is due to physics and the specific weather conditions.
- The building was probably completely cooled down, so the high initial consumption is normal.
- We obviously cannot assess any other factors, such as if there are additional elements in the house or how the system is configured, etc.
In general, the last four days have also been the highest consumption period for us since installation...
So the heat pump will work fine; it modulates down to 1.7 kW, while the smaller one ranges from 1.1 to 5 kW and could have worked as well. I don’t consider this one to be completely oversized. Take a look at the menu on the indoor unit (which one? EQ or compact?) and tell me about the heating curve and supply temperature versus outdoor temperature. The question is also whether you are at a high altitude like Zugspitze or somewhere lower like Freiburg.
Previously, only fan heaters were used in the building, so it was not particularly warm. The defrost cycles have decreased somewhat today (about every 2 hours, just above 0°C (32°F) during the day), but the high electricity consumption has not changed significantly. The indoor module is the Compact version, the supply temperature is set to 26°C (79°F), and the system is located in the greater Dresden area. I don’t fully understand how to check the heating curve or how to interpret it.
The installer said today that the issue is because the room thermostats have not yet been installed, all valves are fully open (set manually), and therefore the system is running at full capacity. The setpoint temperature (although I’m not sure where the system gets it from if there are no room thermostats yet) and the heating stop parameter were set by him to 19°C (66°F), which I lowered to 17°C (63°F) today after consulting with him. I’m curious to see how it will look tomorrow...
The installer said today that the issue is because the room thermostats have not yet been installed, all valves are fully open (set manually), and therefore the system is running at full capacity. The setpoint temperature (although I’m not sure where the system gets it from if there are no room thermostats yet) and the heating stop parameter were set by him to 19°C (66°F), which I lowered to 17°C (63°F) today after consulting with him. I’m curious to see how it will look tomorrow...
J
jens.knoedel20 Jan 2024 20:11Sven2617 schrieb:
The flow temperature is set to 26°C (79°F). Sven2617 schrieb:
All valves are fully open (manually set) and the system is therefore running at full load. 26 degrees is quite moderate – it won’t really warm the house up much at first. Full load would be 45-50 degrees. Having all valves fully open is fine because
Sven2617 schrieb:
the room thermostats are not yet installed just means that all rooms are being heated. Room thermostats only switch heating on or off, they don’t regulate flow rate, unless you consider the options 0% or 100% as “regulating.”
Can you read more data on the display? Compressor frequency, supply/return temperatures, pump performance, or something similar?
Defrosting every two hours is acceptable at the moment. Last night, with minus 4°C (25°F), it was every 1.5 hours here, during the day around 0°C (32°F) every three hours.
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RotorMotor20 Jan 2024 20:58As long as you haven't moved in yet, you shouldn't cause any unnecessary concerns. With tradespeople coming and going, and doors and windows left open, the consumption values are not reliable.