A probe in the flue feeds an electronic analyzer that measures O2, CO and stack temperature, calculates CO2, excess air and combustion efficiency, and often reads draft and NOx. Readings are taken at several firing rates and recorded as a combustion report. A burner set up by ear or by flame color can look fine and still produce dangerous CO, which is why techs treat the analyzer as mandatory.
Combustion analysis at high fire: 3.8 O2, 22 ppm CO, 340 net stack, 84.6 efficiency, I'm happy with that.
Let the boiler run at least ten minutes at each rate before you write numbers down; early readings lie.
Also heard as
- combustion test
- flue gas analysis
Related terms
Excess air
Combustion air supplied beyond the exact amount needed to burn all the fuel, expressed as a percentage.
Air-free CO
Carbon monoxide in flue gas corrected to zero excess oxygen, so dilution with air cannot hide a CO problem.
Stack temperature
The temperature of the flue gas as it leaves the boiler, a direct measure of how much heat is going up the chimney.
Dial in
To fine-tune a burner with a combustion analyzer until oxygen, CO and stack temperature land where they belong.