BoilerFaultCodesTechnical description
High temperature lock out (boiler fired dry)
What causes this fault?
This fault occurs when the water inside the heat exchanger becomes too hot too quickly, causing the safety sensors to shut the system down to prevent damage. The most common reason is a lack of water circulation, often caused by a failed pump, a blockage in the pipework, or air trapped within the unit. It can also happen if there is not enough water in the system to carry the heat away from the burner.
This issue is frequently seen in autumn when heating systems are switched back on after a long summer break, as internal pump components can seize up 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.