High
224 on Worcester Bosch Greenstar 4000

Your boiler has detected that it is running dangerously hot and has shut itself down to prevent internal 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.

Technical description

Maximal flue gas thermostat or heat exchanger maximal thermostat has activated

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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