BoilerFaultCodesTechnical description
If this thermostat should operate and switch off the appliance it is because the flue is subject to downdraught, probably as a result of adverse wind conditions. It is an automatic reset thermostat with a built-in reset delay in excess of 10 minutes.
What causes this fault?
This fault occurs when the safety sensor detects that poisonous combustion gases are failing to rise up the chimney and are instead spilling back into your home. The most common reasons are a physical blockage in the flue, such as a bird's nest, or severe wind conditions pushing the air back down the pipe.
This issue is most frequent during autumn and winter when high winds are more common or when debris like fallen leaves and nests block the chimney.
Engineer required
This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.