E23
ACV
Combustion Fault / CO₂ Out of Range
Boiler displays E23, burner stops, may be associated with low flue gas recirculation margin
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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
Incorrect gas valve adjustment, Blocked burner, Wrong gas type setting, Flue restriction
How to Fix / Troubleshooting
Safety first: Risk of unsafe combustion. Do not continue to reset and run the boiler with this error.
- Check flue terminal: Ensure the ACV flue outlet is clear as previously described.
- Do not adjust gas valve: Gas valve and combustion settings must only be adjusted by a qualified technician with a flue gas analyzer.
- Record symptoms: Note any unusual smells, noises, or visible signs at the flue terminal and report them to the technician.
- Professional service: A technician must clean the burner and heat exchanger, verify gas type and pressure, and adjust combustion to ACV specifications.
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Repair Difficulty
Professional Required
5/5
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