BoilerFaultCodesTechnical description
Water pressure greater than 2.9 bar
What causes this fault?
This fault occurs when the internal water pressure exceeds safe operating limits, often because the manual filling loop has been left slightly open or has a slow leak. It can also be caused by a failure in the expansion vessel, which is the part responsible for managing water expansion as it heats up. Without space for the water to expand, the pressure rises rapidly until the boiler shuts down to prevent internal damage.
This issue often surfaces in winter when the heating is first turned on for long periods, as the constant heating and cooling of water exposes faults in the expansion vessel.
DIY fix possible
Check that the internal or external filling loop valves are fully closed.Bleed water from a radiator using a radiator key to reduce the system pressure.Monitor the pressure gauge on the boiler control panel to ensure it returns to between 1.0 and 1.5 bar.