BoilerFaultCodesYour boiler has detected a problem safely discharging exhaust gases or removing waste water, causing it to shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Error with the NTC (Negative Temperature Coefficient) flue, air pressure switch or blocked flue or condensate
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that the exhaust gases are too hot or cannot escape the property correctly. It is often triggered by a breakdown in the sensor that monitors flue temperatures, or a physical blockage in the pipe that carries waste water away from the unit. When the system can no longer safely vent heat or clear condensation, it shuts down to prevent internal damage.
This fault is significantly more common during freezing winter temperatures, as the external condensate drainage pipe can freeze solid and cause a backup into the boiler.
DIY fix possible
Check the external plastic condensate pipe for signs of freezing or blockageGently pour warm water over the external pipe if it is frozenEnsure the external flue terminal on your wall is not obstructed by debris or plantsReset the boiler once by turning the selector knob to 'R' for five seconds
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