A combustion tune-up sets the ratio of fuel to air at the burner. A burner needs some air beyond what the fuel strictly uses, or part of the fuel goes unburned and forms carbon monoxide. Too much extra air has its own cost: it gets heated and carried out the stack.
The ratio has to be right across the whole firing range, not at one point. A burner set correctly at high fire can be well off at low fire, and most boilers spend much of their time between the two.
A tune-up starts on the fuel side: gas or oil pressure, regulators, and pressure switches. Settings made on top of a fuel supply problem don't hold. Next, a combustion analyzer goes in the stack and the burner is stepped from low fire to high fire. At each point, air and fuel are adjusted to bring O2 down as far as it will go while CO stays low and the flame stays stable. The last steps are checking the safety controls and flame signal and recording the before-and-after readings.
The U.S. Department of Energy's rule of thumb is that boiler efficiency rises about 1% for every 15% reduction in excess air. On a boiler that runs year-round, that adds up over a year of fuel. A tune-up also turns up the causes of nuisance trips, reduces soot on oil burners, and gives you a dated report for your insurer and boiler inspector.
Once a year is a common baseline for commercial and industrial boilers, plus any time the burner, fuel, or controls change.
Signs a burner has drifted: a yellow or lazy flame, stack temperature rising at the same load, more lockouts than usual, or fuel use going up when the load hasn't.
Related reading: Excess Air and O2, What a Combustion Report Shows and What an Out-of-Tune Burner Really Costs. See all of our services on the What We Do page.
Need a tune-up with a written report? Request service or email service@combustionspecialists.com.
