Boiler attempts to start but shuts down with lockout, fan runs but no flame, often after several ignition attempts

Safety: Isolate power and fuel before opening the boiler casing. Only competent persons should work on combustion components.

• Visual check: Remove the burner cover and inspect the ionisation electrode. Clean any soot or oxidation with fine abrasive. Ensure the electrode is not cracked and is firmly fixed.
• Check wiring and earth: Verify that the ionisation lead is securely connected to the control box and that the burner has a solid earth/ground connection to the boiler chassis. Tighten any loose terminals.
• Fuel pressure check (basic): Confirm that all isolation valves are open and that there is adequate fuel in the tank (oil) or that other gas appliances are working normally (gas). If you suspect low pressure, stop and call a professional.
• Reset and test: Restore power, press the reset button once, and observe the ignition sequence through the sight glass. If the flame appears briefly then goes out, the flame sensing circuit may be faulty.
• Professional service: A heating engineer should measure ionisation current, verify gas valve or oil pump pressures, and test/replace the Riello burner control box if necessary.