A pressurisation unit is an integral component to most heating systems.
This is mostly overlooked come service time.
At energy Tech NI we provide a complete service of these units and associated expansion vessels. Checks include pump operation and low/high pressure alarms.
Expansion vessels if not maintained, can lead to variations in system pressure which in turn can lead to system faults/safety valves lifting. Keeping an air cushion pressures at the right settings, will avoid unnecessary down time.