High Lockout
78 on Worcester Bosch Greenstar Utility 18/25

Your boiler is having trouble creating the spark or flame needed to start up because the internal ignition components are out of alignment.

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

Electrode settings incorrect

What causes this fault?

This fault occurs when the spark electrodes inside the boiler's burner move out of their precise position or become worn down over time. Without the correct spacing, the boiler cannot create a strong enough spark to ignite the fuel, or it may fail to detect that a flame has successfully started.

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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