A well-tuned burner does not in itself mean that the entire boiler is operating at maximum possible efficiency.
Combustion efficiency
It primarily concerns how correctly the fuel is burned and how many losses occur through flue gases.
Boiler efficiency
It additionally includes thermal losses from the body, the heat exchanger, the standby losses, and actual load conditions.
Clean heat exchanger
A burner may have good O₂ and CO values, but a dirty heat exchanger can significantly limit heat transfer.
Overall evaluation
A combination of proper combustion, a clean heat exchanger, and appropriate system operation is required.
