Boiler shows high pressure alarm, pressure gauge above safe range, safety valve may discharge water

Safety first: High pressure can cause hot water discharge. Keep clear of the pressure relief valve outlet when venting.

• Check pressure reading: If pressure is above 2.5–3.0 bar, the system is over-pressurised.
• Isolate filling loop: Ensure both filling loop valves are fully closed and the flexible hose is removed if the design allows. A slightly open valve is a common cause of overfilling.
• Reduce pressure safely: Bleed a radiator using a radiator key into a container until the pressure drops to around 1.5 bar. Alternatively, a technician can use the boiler’s drain point.
• Inspect expansion vessel: If pressure rises rapidly when the boiler heats, the expansion vessel may have lost its air charge. This requires a technician to check and recharge or replace the Nibe expansion vessel.
• Check discharge pipe: Look outside at the copper safety discharge pipe. If it is dripping regularly, the pressure relief valve may be damaged and should be replaced by a professional.