BoilerFaultCodesTechnical description
Boiler has entered lockout mode. Can be caused by the overheat cut-off going open circuit or failure to detect flame.
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that the unit has become dangerously hot or that the gas has failed to ignite after several attempts. The most common reasons are a lack of water circulation causing the heat exchanger to trap too much heat, or worn-out ignition parts that can no longer create a spark to light the burner.
This issue is more frequent during the first cold snap of autumn when pumps that have been idle all summer often seize up, leading to immediate overheating.
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.