High
FAIL POINT H Burner Lockout on Worcester Bosch Greenstar Si

Your boiler has stopped working because it cannot ignite the flame needed to heat your water and radiators, possibly due to a gas supply problem or an issue with the internal ignition system.

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

Burner Lockout. Gas supply issue, spark electrode/HT lead failure, gas valve resistance/harness fault (contacts 7, 8, 9, 10), or flame sensor failure.

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
Search the official register →

Related guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Pilot light keeps going out

Older boilers — thermocouple, draught, gas supply.

Read →

Radiators cold at the bottom

Sludge build-up — needs flushing, not bleeding.

Read →