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

Your boiler has detected that fumes are not escaping properly through the flue and has shut itself down for your safety.

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

Products Discharge Safety Device (TTB) - CF Only: In the case of flue blockage this device will operate and the boiler will go 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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