ᐅ Ground Source Heat Pump: Bathroom on the Top Floor Too Cold – Is the Heat Distribution Incorrect?
Created on: 27 Dec 2025 15:47
D
dassmoo
Hello,
I am a bit puzzled. Our attic bathroom feels too cold for my wife, and—assuming the cheap thermostat is accurate—the temperature is only about 19°C (66°F). What can I do?
About our heat pump:
We have a ground-source heat pump from Viessmann, with the heating circuit set to 21°C (70°F) from 6 a.m. to 10 p.m. The heat pump is located in the basement. Above that are the ground floor, then the first floor, and finally the attic (so the water has to be pumped up three levels). Whether the heating curve is set to a slope of 0.4 and a base value of 0.0, or a slope of 0.4 and a base of -1.0, the attic bathroom always stays cooler. When the plumbing company was here recently, they checked and found that two of the valves in the heating distributor manifold were not opening properly, and they replaced them (these valves served other circuits on the same attic floor). After that, they used a thermal imaging camera and noted that it was 21°C (70°F). That day, however, the sun was shining. Usually, the thermometer shows a lower temperature.
I just checked the flow rate for the heating circuit at the distributor manifold. It is about 2.4. If I turn it clockwise, the flow decreases (which I don’t want). If I turn it counterclockwise, it reaches a stop at 2.4. It cannot be increased any further in that direction.
The wall thermostat in the bathroom is set to “6” (scale from 1 to 6). What else can I do? I would appreciate any help.
I am a bit puzzled. Our attic bathroom feels too cold for my wife, and—assuming the cheap thermostat is accurate—the temperature is only about 19°C (66°F). What can I do?
About our heat pump:
We have a ground-source heat pump from Viessmann, with the heating circuit set to 21°C (70°F) from 6 a.m. to 10 p.m. The heat pump is located in the basement. Above that are the ground floor, then the first floor, and finally the attic (so the water has to be pumped up three levels). Whether the heating curve is set to a slope of 0.4 and a base value of 0.0, or a slope of 0.4 and a base of -1.0, the attic bathroom always stays cooler. When the plumbing company was here recently, they checked and found that two of the valves in the heating distributor manifold were not opening properly, and they replaced them (these valves served other circuits on the same attic floor). After that, they used a thermal imaging camera and noted that it was 21°C (70°F). That day, however, the sun was shining. Usually, the thermometer shows a lower temperature.
I just checked the flow rate for the heating circuit at the distributor manifold. It is about 2.4. If I turn it clockwise, the flow decreases (which I don’t want). If I turn it counterclockwise, it reaches a stop at 2.4. It cannot be increased any further in that direction.
The wall thermostat in the bathroom is set to “6” (scale from 1 to 6). What else can I do? I would appreciate any help.
nordanney schrieb:
That's right. At the same time, in the possibly somewhat cooler attic, the desired temperature in the bathroom isn’t reached. Just let it run for a while. Maybe it will improve a bit.
By the way, is the heating water color supposed to look like that? It looks murky – with our last brine heat pump it was clear.I have no idea, but it does actually look dirty. The heating system is from 2023. A quick search makes me think that during the next maintenance, a sample should be taken and possibly a fluid replacement done?