Display shows A14; water heater indicates legionella protection fault or failed high-temperature cycle.

Safety first: High-temperature cycles can cause scalding. Ensure mixing valves are correctly set and warn occupants before testing.

This alarm indicates that the scheduled legionella protection cycle (high-temperature disinfection) did not complete correctly.

• Step 1 – Check settings:
  • In the Nibe menu, verify the legionella function is enabled and the target temperature (e.g. 60–65 °C) and duration are correctly set.
• Step 2 – Verify heater capacity:
  • Ensure the immersion heater or external heat source is sized to reach the required temperature.
  • Check for A10 or other heater-related alarms.
• Step 3 – Sensor accuracy:
  • Confirm that the tank sensor readings are realistic; faulty sensors can cause premature termination.
• Step 4 – Manual cycle:
  • Trigger a manual legionella cycle and monitor the temperature rise.
  • If the tank cannot reach the setpoint, investigate heater performance or scale buildup.

If the alarm recurs despite correct settings and functioning heaters, consult Nibe support for firmware or control logic issues.