BoilerFaultCodesTechnical description
The automatic test for calibration of flow and return sensors has failed – check both flow and return sensors are located on the correct pipes and are producing the correct readings
What causes this fault?
This fault occurs when the boiler's control chip detects that the temperature sensors on the outgoing and incoming pipes are giving contradictory information during a startup check. The most common reason is that one of the sensors has drifted out of calibration or has been physically loosened from its pipe, meaning the boiler can no longer safely calculate how much heat it is generating. In some cases, it can also be caused by a faulty wiring connection preventing the signals from reaching the main circuit board correctly.
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.