Emergency
211 on Worcester Bosch Greenstar CDi Compact

Your boiler has sensed that exhaust gases are not escaping properly and has shut down to prevent the buildup of dangerous fumes in your home.

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.

Technical description

TTB opened (thermal kickback device)

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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