BoilerFaultCodesTechnical description
The system has suffered a fault due to overheating.
What causes this fault?
This fault occurs when the internal water temperature rises too quickly or exceeds a safe limit, causing the boiler to shut down to prevent internal damage. The most common reasons are a failed pump that isn't moving water away from the heat exchanger fast enough, or a build-up of debris causing a blockage in the pipework. It can also be triggered if air is trapped in the system or if the radiators are turned off, leaving the heat with nowhere to go.
This fault is more common in autumn when heating systems are turned back on after a long summer break, as pumps can seize during periods of inactivity.
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.