Heat pump expansion vessel: Function and basic principles
The "Heat pump expansion vessel" concerns pressure stabilization and expansion absorption in a heat pump circuit. The vessel's operation is indicated by how stable the pressure remains as the system temperature changes.
Basic technical elements
We examine the buffer (if present), static height, operating temperatures, and total water volume. These four parameters determine if the vessel has sufficient useful volume.
What we measure in practice
Useful measurements include ΔP during defrost, pre-charge, cold pressure, and pressure in heating mode. Values are recorded in both cold and hot states.
Where discrepancies usually appear
Problems may be due to air locks, frequent pressure changes, an undersized vessel, or incorrect pre-charge. In a heat pump, the additional volume of a buffer or hydraulic separator is also taken into account.
Measurement and recording points
- Δp during defrost.
- Pre-charge.
- Cold pressure.
- Pressure in heating mode.
Practical observation
In a heat pump, the additional volume of a buffer or hydraulic separator is also considered. For a correct assessment, we note the system temperature at the time of measurement, as pressure fluctuates along with temperature.
Safety
Before checking or disconnecting an expansion vessel, the hydraulic circuit must be isolated and safely depressurized, confirming that there is no dangerous pressure or temperature. The work should be performed by a suitably qualified technician.
Conclusion
For the "Heat pump expansion vessel," proper operation is verified by correct pre-charge, an appropriate vessel volume, and controlled pressure variation between cold and hot states.