BoilerFaultCodesTechnical description
Heating mode – pump overrun error
What causes this fault?
This issue occurs when heat is trapped inside the boiler's heat exchanger after the heating has turned off, usually because the water isn't moving away quickly enough. The most common reasons are a pump that is beginning to fail, trapped air in the unit, or a build-up of sludge in the system pipes that is restricting flow.
This fault often appears at the start of autumn when the heating is turned back on after a long summer break, as pumps can seize or struggle after being idle for several months.
DIY fix possible
Check that at least one radiator (usually the one in the hallway near the thermostat) is fully turned on at the valves.Ensure the boiler pressure is within the green zone (typically 1.0 to 1.5 bar).Bleed your radiators to ensure there is no trapped air in the system.If the code persists, try resetting the boiler once to clear the status.