F.373 — Burner in a fault state (Heat transfer too low during calibration)

What does F.373 mean?

The burner is in an error state because the heat transfer is too low during calibration, possibly due to the temperature limiter shutting down or issues with the circulation pump or diverter valve.

• Temperature limiter has shut down
• Inadequate heat transfer
• Circulation pump faults, scale, or blockages
• 3-way diverter valve malfunction
• Faulty flow sensor

Click steps to track your progress.

1. 1

   Reset the appliance.

2. 2

   Ensure there is adequate heat transfer in the system (e.g., radiators are not cold, system is not air-locked).

3. 3

   Vent the heating system to remove any airlocks.

4. 4

   If the fault persists, contact a qualified technician to check the circulation pump, 3-way diverter valve, or flow sensor.