BoilerFaultCodesYour boiler has shut down because there is too much water pressure in the central heating system.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: Primary pressure over 3 bar, boiler off. Reduce CH system pressure. Check/adjust/replace primary expansion vessel
What causes this fault?
This fault occurs when the water pressure inside your heating system exceeds a safe working limit, forcing the boiler to shut down to prevent damage. The most common reason is that the internal expansion vessel, which normally absorbs the pressure of expanding hot water, has failed or lost its air charge. It can also be caused by a filling loop being left slightly open, which allows water to continuously leak into the system.
This fault is more common in winter when the heating is first turned on for long periods, as the increased heat causes water to expand and reveals issues with the expansion vessel.
DIY fix possible
Locate a radiator bleed valve and use a key to release water into a container to lower the pressure.Ensure the filling loop valves are tightly closed to prevent more water entering the system.Monitor the pressure gauge until it returns to between 1.0 and 1.5 bar.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like P3.0-3.5 — no call-out fees, no surprises.
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