BoilerFaultCodesTechnical description
The safety devices have been activated (lockout)
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the water temperature has risen too quickly or peaked beyond safe limits. The most common reason is a failure in the circulation pump or a blockage in the heat exchanger, preventing heat from being moved away from the burner. It can also be triggered if there is air trapped in the system or if the water pressure has dropped too low to function.
This issue often surfaces during the first cold spell of autumn when a pump that has been idle all summer fails to restart correctly.
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.
Find a Gas Safe engineer
Search the official register →