Boiler displays F.02 and shuts down shortly after starting, flame proves then drops out

Safety first: Switch off power and close the gas shutoff valve before inspection. Allow the boiler to cool.

• Check venting and air intake: Inspect the PVC/CPVC intake and exhaust pipes from the boiler to the termination. Look for sagging sections, water accumulation, bird screens clogged with debris, snow/ice blockage, or insect nests. Clear any obstructions and ensure terminations meet Lochinvar installation clearances.
• Inspect condensate drain: A backed-up condensate trap can affect combustion. Locate the condensate trap and tubing. Verify the trap is not plugged with debris or sludge. Flush with clean water and reassemble, ensuring all hoses are secure and sloped for drainage.
• Clean burner and flame sensor: Remove the burner assembly per the service manual. Vacuum dust and debris from the burner surface. Clean the flame sensor rod with fine abrasive pad. Reinstall carefully.
• Check gas supply stability: Confirm that other gas appliances are not causing pressure drops (e.g., multiple large appliances starting simultaneously). If you suspect gas pressure issues, do not adjust anything yourself—contact a licensed gas technician.
• Reset and monitor: Restore power and gas, reset the boiler, and observe operation. If F.02 recurs, a technician should measure combustion, gas pressure, and flame signal.

Professional help: Persistent F.02 faults often require combustion analysis and gas valve testing, which must be done by a qualified technician with proper instruments.