Emergency
E9 224 on Worcester Bosch Greenstar i

Your boiler has switched itself off because it has detected an unsafe temperature or a blockage in the exhaust flue, preventing it from operating safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

Flue or high limit thermostat activated (safety circuit)

From this model's manual
Verified against the Worcester Bosch Greenstar I 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 emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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