Emergency
Red LED (Lockout) on Potterton Kingfisher MF 40-100

Your boiler has automatically shut down for safety because it has detected a blockage in the chimney or flue that prevents dangerous exhaust gases from escaping.

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 Products Discharge Safety Device (TTB) has operated due to a flue blockage (CF Models Only).

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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