High
LOCKOUT LIGHT ON (CONSTANTLY) on Worcester Bosch Greenstar 15sbi

Your boiler has detected that it is getting too hot and has automatically shut itself down to prevent damage.

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.

What the manual says

Manufacturer manual

FAULT POINT D. Boiler overheat. Possible causes: system not pressurised, air in system, bypass missing/incorrect, pump failure, sensor fault, or overheat thermostat tripped.

From this model's manual
Verified against the Worcester Boiler 9 14 Cbi installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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