Unit locks out with F2, burner shuts down shortly after ignition or during operation

Safety first: Isolate electrical power and close the gas valve. Wait until the combustion chamber is cool before working near the burner.

• Inspect ionization electrode: Remove the burner cover. Locate the ionization electrode near the burner. Check for cracks in the ceramic, soot deposits, or corrosion on the metal rod.
• Clean electrode and burner: Gently clean the electrode rod and burner surface with fine emery cloth or a non-metallic abrasive pad. Do not bend the electrode out of its specified position.
• Check cable and grounding: Inspect the high-voltage/ionization cable for burns, cuts, or loose terminals. Ensure the burner and gas valve are properly grounded to the chassis.
• Verify gas pressure and combustion: Low gas pressure or incorrect air/gas ratio can cause unstable flame. A qualified technician should measure inlet and burner pressure and adjust according to Protherm specifications.
• Replace electrode or PCB: If the flame is stable but F2 persists, replace the ionization electrode and cable. If still unresolved, the flame detection circuit on the main PCB may be faulty and the board should be replaced.

Warning: Combustion adjustments and gas pressure checks must only be performed by licensed gas technicians.