Emergency
Red LED (TTB) on Potterton Kingfisher MF RSL

Your boiler has detected that fumes are not escaping properly through the flue, so it has shut itself down automatically to keep you safe from harmful exhaust gases.

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

The red LED will be illuminated in the case of flue blockage (CFL Only) when the Products Discharge Safety Device (TTB) operates and the boiler goes to lockout.

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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