H
Häuslebauer3615 Jan 2026 16:38Hello everyone,
I have the above-mentioned air-source heat pump with an external buffer tank of 45L (12 gallons) and an external expansion vessel. Additionally, there is an external Optinline pump for the underfloor heating system.
I am using the setup in a KFW45 energy-efficient house. It was installed by a plumbing company in the summer of 2025.
Problem:
The compressor now starts about 3-4 times per hour on average during the cold season.
I have all the actuators (with open room thermostats) fully open. The flow rate at the valves is everywhere ≤1 l/min (0.26 gallons/min).
The Optinline pump is set to 2.0 m (6.6 feet) for a house with a ground floor, first floor, and second floor.
Yesterday, I measured the individual heating circuits directly on the pipes at the manifold using a laser thermometer. It was apparent everywhere that the supply and return temperatures are almost identical, with sometimes just a 1-degree difference.
This indicates a thermal short circuit, meaning the floor is not able to absorb the heat, right? It is also warmer downstairs than upstairs in the house.
The heating temperature differential (ΔT) is set to 5.
What adjustments might help solve these problems? Could any sensors or connections be swapped? The pipes seem to be connected correctly.
I’m slowly getting frustrated with this issue. The plumbing company is also very reserved on the matter.
Thanks and best regards,
Phil
I have the above-mentioned air-source heat pump with an external buffer tank of 45L (12 gallons) and an external expansion vessel. Additionally, there is an external Optinline pump for the underfloor heating system.
I am using the setup in a KFW45 energy-efficient house. It was installed by a plumbing company in the summer of 2025.
Problem:
The compressor now starts about 3-4 times per hour on average during the cold season.
I have all the actuators (with open room thermostats) fully open. The flow rate at the valves is everywhere ≤1 l/min (0.26 gallons/min).
The Optinline pump is set to 2.0 m (6.6 feet) for a house with a ground floor, first floor, and second floor.
Yesterday, I measured the individual heating circuits directly on the pipes at the manifold using a laser thermometer. It was apparent everywhere that the supply and return temperatures are almost identical, with sometimes just a 1-degree difference.
This indicates a thermal short circuit, meaning the floor is not able to absorb the heat, right? It is also warmer downstairs than upstairs in the house.
The heating temperature differential (ΔT) is set to 5.
What adjustments might help solve these problems? Could any sensors or connections be swapped? The pipes seem to be connected correctly.
I’m slowly getting frustrated with this issue. The plumbing company is also very reserved on the matter.
Thanks and best regards,
Phil