ᐅ Air-to-water heat pump supply temperatures

Created on: 17 Nov 2020 18:10
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lesmue79
I am currently experimenting with my heating curve and would be interested to know what supply temperatures you are running with your air-to-water heat pump combined with underfloor heating?
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Bookstar
18 Nov 2020 06:05
blackm88 schrieb:

Outside temperature currently 5.1 degrees, return temperature 24.2, supply temperature 24.4. Room temperature 22-24 degrees
How can the difference between return and supply be only 0.2 degrees? Your heat pump is either off or not running.

My current data with 5 degrees outside: supply temperature 29.8 degrees, return temperature 25 degrees, room temperature 22.5 degrees.

You should not forget that most (all?) heat pumps are controlled by the return temperature. That means you set the maximum return temperature on your heating curve! This is usually somewhere around 27-30 degrees. This means, in extreme cases, a supply temperature up to 33-35 degrees. Although it rarely gets that cold.
B
Bookstar
18 Nov 2020 06:40
Bookstar schrieb:

How can the temperature difference between return and supply be only 0.2 degrees? Your heat pump is standing still and not running.

My current data at 5 degrees outside: supply 29.8 degrees, return 25 degrees, room temperature 22.5 degrees.

You must not forget, most (all?) heat pumps are controlled by the return temperature. That means you set the maximum return temperature on your heating curve! This is usually somewhere around 27–30 degrees. That means in extreme cases the supply can be up to 33–35 degrees, although it rarely gets that cold.

I’m updating with more recent data: 29 degrees supply, 26.4 degrees actual return, 26.4 degrees target return. Hysteresis is 1.5 degrees, so it is heating right now. Outdoor temperature is 1 degree Celsius.
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lesmue79
18 Nov 2020 06:53
Okay, that sounds more interesting. I was just wondering if a supply temperature of around 26°C (79°F) is normal when the room temperature is about 20–21°C (68–70°F) and it’s approximately 8°C (46°F) outside. According to calculations, the system should be able to handle a maximum supply temperature of 30°C (86°F) at an outside temperature of minus 12°C (10°F), so I was surprised to already have 26°C (79°F) supply temperature when it’s not even freezing outside.
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halmi
18 Nov 2020 08:16
What building standard is your house constructed to? I assume you currently have a cozy 19°C (66°F) inside your home?
blackm8818 Nov 2020 08:16
My heat pump actually runs only from 8 a.m. to 5 p.m., but only in short cycles. Currently, the outside temperature is 3.1°C (37.6°F), and the supply temperature is now 24.9°C (76.8°F) at 20 liters.
B
Bookstar
18 Nov 2020 08:16
lesmue79 schrieb:

Okay, that sounds more interesting. I was just wondering if a supply temperature of around 26°C (79°F) is normal when the room temperature is about 20-21°C (68-70°F) and it’s about 8°C (46°F) outside. According to calculations, the system should manage with a maximum supply temperature of 30°C (86°F) at minus 12°C (10°F) outside, so I was surprised that I’m already at 26°C (79°F) supply temperature and it’s not even freezing yet.
No, that won’t work. You will need to run a higher supply temperature. Where does that assumption come from?