High Lockout
E80-451 on Worcester Bosch 24/28CDi II RSF

Your boiler has detected a specific internal electronic fault with the valve that controls the gas supply, meaning the appliance cannot ignite safely and will remain shut down.

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

Gas Valve – Propane Dungs BM771 SL 040

What causes this fault?

This fault occurs when the boiler's main control board loses communication with or detects an electrical failure within the gas valve assembly. The most common reason is an internal component failure inside the valve itself, which prevents it from opening to allow fuel into the burner for ignition.

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.

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