High Lockout
FA306 on Worcester Bosch Greenstar Si Combi / i System

Your boiler thinks it can still see a fire inside even though it has commanded the burner to turn off.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

False flame fault – flame detected after burner stop

What causes this fault?

This fault occurs when the boiler's sensors continue to detect a flame even after the gas supply should have been cut off. The most common reasons are a faulty sensor sending an incorrect signal, a gas valve that is physically stuck open, or a damaged control board that is misinterpreting electrical signals.

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
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Related fault codes

FD 231View →EA 227View →F7 228View →

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