Pressurisation Unit Repair London

Common pressurisation unit faults

The alarms tell you the symptom; the cause is usually elsewhere. A low pressure alarm means the system is losing water — a leak, a passing safety valve, or a failed expansion vessel allowing pressure to swing and discharge. A high pressure alarm often means the fill solenoid is passing or the expansion vessel is waterlogged so there is nowhere for the expanded volume to go. A unit that runs continuously has either a genuine leak to find or a non-return valve letting system water back into the break tank.

• Low pressure alarms and system water loss
• High pressure alarms and safety valve discharge
• Passing fill solenoids and non-return valves
• Failed pressure sensors and controllers
• Pump failure on single and twin pump units
• Break tank float valve and level switch faults

Finding why the system loses pressure

Repairing the unit without finding the leak just automates the water loss, and continuous fresh water into a sealed system brings oxygen and scale with it, which damages boilers, pumps and heat exchangers. We record fill frequency and volume, pressure test sections, check the safety valve for passing and test the expansion vessel pre-charge, then trace genuine leaks using the appropriate method. Only then do we repair the unit itself and reset it to the correct fill and alarm pressures.

• Fill frequency and make-up volume logged
• Safety valves checked for passing
• Expansion vessel pre-charge tested
• Leak tracing on system pipework
• Correct fill, alarm and set pressures restored

Expansion vessels and pressurisation working together

A pressurisation unit and an expansion vessel are two halves of one system. The vessel absorbs expansion as the system heats; the unit makes up losses and holds the cold fill pressure. If the vessel is waterlogged the pressure swings hard on every heat-up, the safety valve lifts, the system loses water, and the unit dutifully replaces it — so the unit looks faulty when the vessel is the problem. We always test both together, which is why our repairs tend to stay fixed.

Plant rooms, blocks and commercial buildings

Most pressurisation units we attend are in commercial plant rooms and residential block plant, where a lockout means no heating or hot water for an entire building. We attend the same day, get the system pressurised and the boilers running, and report in writing on the root cause and any remedial work needed. Where a unit is obsolete or repeatedly failing we quote a replacement of the correct capacity for the system volume and static height.

• Same-day plant room attendance
• Boilers returned to service quickly
• Written root cause report for agents and FM teams
• Replacement units sized to system volume and height