F27
Protherm Flame Detection / False Flame Signal

F27 error, appliance detects flame when there should be none or vice versa

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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

Ionization electrode contaminated or mispositioned, Electrical leakage to earth, Incorrect grounding, Faulty flame detection circuit on PCB

How to Fix / Troubleshooting

Safety first: Turn off power and gas. Wait for the burner to cool.

  • Inspect ionization electrode: Clean the electrode and burner surface, ensuring correct gap and position.
  • Check grounding: Verify that the appliance is properly earthed and that there are no loose earth connections.
  • Inspect wiring: Look for damaged insulation or moisture on the ionization cable and connectors.
  • PCB diagnosis: If false flame is still detected with gas off and electrode disconnected, the PCB is likely faulty and must be replaced.

Warning: Do not operate the heater with unreliable flame detection; this is a critical safety function.

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Repair Difficulty

Hard 4/5

Required Part

Ionization Electrode
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