Your boiler has stopped working for safety reasons and needs to be reset manually to try and restart the system.

Lockout

What causes this fault?

This fault occurs when the boiler has tried to ignite several times but failed to detect a flame, causing the system to shut down for safety. The most common reasons are a lack of gas reaching the burner, a worn-out ignition spark, or the boiler's internal sensor not recognising that the flame has lit.