BoilerFaultCodesTechnical 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.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.