BoilerFaultCodesTechnical description
Burner lock out. Check gas supply. Check water pressure in central heating system, refill and vent as necessary. Check if pump is running. Check pump plug connection. Replace electronic board.
What causes this fault?
This fault occurs when the boiler's control system senses that the water temperature is rising far too quickly, usually because the heated water cannot leave the heat exchanger fast enough. The most common reasons are a failing central heating pump that isn't circulating the water or a physical blockage caused by a build-up of sludge and debris in the pipework.
This fault is more frequent in autumn when the heating is first turned on after being dormant all summer, which can cause internal pump components to seize.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.