Emergency
Flue blockage on Potterton Kingfisher MF 40-100

Your boiler has detected that waste gases are not escaping correctly through the flue, so it has safely shut itself down to prevent harmful fumes from entering 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.

What the manual says

Manufacturer manual

Products Discharge Safety Device (TTB) operates; boiler goes to lockout (Red LED illuminated, requires manual reset)

From this model's manual
Verified against the Potterton Kingfisher Mf 40 100 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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