F28
Protherm Ignition Lockout (No Flame Detected)

F28 displayed, ignition attempts fail, no flame established

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

No gas supply, Air in gas line, Faulty ignition electrode or cable, Defective gas valve, Incorrect gas pressure

How to Fix / Troubleshooting

Safety first: Turn off power and gas. Ventilate the area if gas smell is present. Only gas-qualified personnel should proceed beyond basic checks.

  • Check gas supply: Ensure the gas isolation valve is open and other gas appliances work.
  • Bleed air: After new installation or long shutdown, a technician should safely purge air from the gas line.
  • Inspect ignition system: Clean and check the ignition electrode and cable for damage or misalignment.
  • Measure gas pressure: A technician should verify inlet and burner pressure and adjust the gas valve if necessary.
  • Replace gas valve or PCB: If the valve does not open or no gas reaches the burner, replace the gas valve. If the valve is not energized, the PCB may be faulty.

Warning: Never attempt to light the burner manually or bypass safety controls.

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Repair Difficulty

Professional Required 5/5

Required Part

Gas Valve Assembly
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