ᐅ Adjusting the Flow Rate of Underfloor Heating with an Air Source Heat Pump
Created on: 27 Dec 2025 15:28
D
delbau
Hello everyone,
We have been living for some time now in our well-insulated house with an air source heat pump and underfloor heating. We have properly set up the air source heat pump and have turned off the thermostats.
However, one room is always too warm while another is too cold.
Therefore, I would like to slightly adjust the flow rate of the underfloor heating.
That means increasing it in the cold room and decreasing it in the warm room.
It seems that this can be done using the small tubes on the supply line.
One of the tubes had the square section broken off at the top from the start, which was done by the heating installer.
I have now carefully tried to adjust the flow by turning it, but the tube does not move, and I am worried about breaking it.
Am I correct in assuming that the tube must really be turned using the square section?
Can it be damaged mechanically like that? I would rather avoid causing a water leak :-)
We have been living for some time now in our well-insulated house with an air source heat pump and underfloor heating. We have properly set up the air source heat pump and have turned off the thermostats.
However, one room is always too warm while another is too cold.
Therefore, I would like to slightly adjust the flow rate of the underfloor heating.
That means increasing it in the cold room and decreasing it in the warm room.
It seems that this can be done using the small tubes on the supply line.
One of the tubes had the square section broken off at the top from the start, which was done by the heating installer.
I have now carefully tried to adjust the flow by turning it, but the tube does not move, and I am worried about breaking it.
Am I correct in assuming that the tube must really be turned using the square section?
Can it be damaged mechanically like that? I would rather avoid causing a water leak :-)
I have a strong suspicion that a hydraulic balancing was never carried out.
All flow meters roughly show a consistent flow of 1 liter, and 1.5 liters during heating operation – regardless of how far the heating circuit is located.
I have now reduced the flow in the room that was too warm to about 0.8 liters, but I couldn’t increase the flow in the room that was too cold because its valve was already fully open.
How would you approach this situation?
It is a new build from 2017, and hydraulic balancing was actually mandatory at that time.
All flow meters roughly show a consistent flow of 1 liter, and 1.5 liters during heating operation – regardless of how far the heating circuit is located.
I have now reduced the flow in the room that was too warm to about 0.8 liters, but I couldn’t increase the flow in the room that was too cold because its valve was already fully open.
How would you approach this situation?
It is a new build from 2017, and hydraulic balancing was actually mandatory at that time.
tomtom79 schrieb:
Ours are on a separate circuit breaker. Do you happen to have that kind of luck?Unfortunately not, the electrician had everything connected to one.
Which room is the one with the 0.8 liters? Hopefully not the bathroom, although you can add an external heat source there temporarily. We have a fan heater mounted on the wall that raises the room temperature by at least 3 degrees Celsius (5°F) within 5 minutes. That small amount of kW is cheaper than running the system all day with a higher flow temperature.
We have also tried infrared heating, but the warmth felt uncomfortable.
Unfortunately, you can now only increase this room’s temperature by adjusting the supply and return temperatures. However, that also increases consumption. If the flow in this room is constantly active, it might take a while to reach the desired temperature.
Make sure that the heating cycle is running when making adjustments.
We have also tried infrared heating, but the warmth felt uncomfortable.
Unfortunately, you can now only increase this room’s temperature by adjusting the supply and return temperatures. However, that also increases consumption. If the flow in this room is constantly active, it might take a while to reach the desired temperature.
Make sure that the heating cycle is running when making adjustments.
Well, the reduced amount of heated air for the too warm room is redistributed among all the others. So, theoretically, you can slightly reduce the airflow to all the other rooms except for the too cold one. Then, the entire difference should go to the fully open room. The problem is, you won’t know within minutes if that has been enough. So this turns into more of an experiment lasting days, if not weeks.
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