Emergency Lockout
F7 on Worcester Bosch ZWB 7-25

Your boiler has detected a flame signal when it is supposed to be turned off, which suggests a potential fault in the burner control system.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description

Flame detected even though the appliance is switched off.

What causes this fault?

This fault occurs when the boiler's internal sensor continues to detect a flame signal after the heating cycle has finished. It is usually caused by a carbon-coated ionisation electrode providing a false reading, or a gas valve that isn't sealing completely, allowing a tiny amount of gas to keep burning. Because the boiler believes a flame is present when it shouldn't be, it enters a safety lockout to prevent overheating.

Engineer required

This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

EAView →F0View →

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