Your boiler has shut down completely for safety reasons and will not provide heating or hot water until it is manually reset or repaired.

Safety LOCK-OUT condition

What causes this fault?

This fault occurs when the boiler's control system detects a failure in the ignition process or a safety breach, leading to an immediate shutdown. The most common reasons include the burner failing to light, a loss of flame signal during operation, or an internal component like the fan or gas valve not responding correctly. It is a protective measure designed to prevent the boiler from running in an unsafe condition.