The heat pump requires a minimum water flow to protect the heat exchanger and operate stably.
When zones close
The flow can drop sharply if solenoid valves, fan coils, or underfloor loops are shut off.
Differential bypass
It can open when the differential pressure increases to maintain a minimum flow path.
Caution with settings
If it is open too much, it can cause a low ΔΤ and recirculation without actual efficiency in the building.
