Boiler locks out with A03, burner shuts down shortly after ignition or during operation

Safety: Switch off power and close gas supply before opening the combustion chamber. Only trained personnel should work on combustion components.

• Check flue and air intake: Ensure the concentric flue terminal is not blocked by leaves, snow, or debris. Verify that the air intake is clear and that flue joints are secure.
• Inspect burner surface: Remove the burner assembly as per Hoval service instructions. Check for soot, corrosion, or debris on the premix burner surface. Clean gently with a soft brush; do not damage the mesh.
• Clean ionisation electrode: Remove and clean the electrode tip. Check cable integrity and correct positioning in the flame.
• Gas supply stability: If other gas appliances show issues or if the boiler frequently loses flame at high demand, have a technician measure dynamic gas pressure and adjust or report to the gas supplier.
• If flame loss continues, a Hoval technician should perform a combustion analysis and check burner and gas valve settings.