In hydronic and water systems, the air precharge pressure of expansion vessels must be set according to both the building height and the system conditions.
For example, a building with a height of 40 meters creates a static pressure of about 4.0 bar. The expansion vessel should be charged to a pressure close to this value before operation.
A common problem in the field is that technicians often recharge the vessel without checking the required value. If the air pressure is set too low, the vessel will not absorb expansion water properly, leading to frequent safety valve discharges. If the pressure is set too high, water will not enter the vessel, resulting in unstable system operation.
Setting the vessel to the right pressure may seem like a small detail, but it has a major impact on system safety, efficiency, and service life.