How to Fix / Troubleshooting

Safety: Combustion and flue work must be carried out by a qualified gas engineer with a flue gas analyser.

Inspect flue terminal: Ensure the terminal is clear of obstructions and installed according to Immergas clearances.
Check flue components: Verify that all flue joints are secure and that the inner and outer pipes are correctly aligned. Look for signs of condensate leakage or corrosion.
Fan and venturi check: Inspect the fan and venturi for blockages or damage. Clean any debris and ensure the venturi is correctly fitted.
Combustion analysis (engineer): Perform a flue gas analysis and adjust the gas valve (if adjustable) to achieve the correct CO₂/O₂ values as per Immergas specifications.
Re-test: After adjustments, run the boiler at minimum and maximum output to confirm stable combustion and no recurrence of error 27.

Boiler displays error 27, often related to flue gas recirculation or combustion issues.

Possible Causes