Excess combustion air is defined as any air that is not necessary to burn all of the fuel. Excess air can rob boiler and furnace systems of efficiency because it takes energy to heat the excess air not utilized in the combustion process, and most of this heat is lost up the stack. Better air management can lead to significant improvements.

An example of better air management is at a major car manufacturer in the Midwest where approximately 240,000 vehicles are manufactured per year. Large air handlers with direct-fired natural gas burners were used to remove paint overspray during the paint finishing process. They were looking for improved temperature control and reduced energy usage. It was determined that by decreasing the speed of their makeup air fans during idle production periods, they could lower electrical costs and gas usage by moving and heating less air.

By installing Maxon APX burners with an electronic micro-ratio valve (SmartLink MRV) system enabling tight control of the air/fuel ratio, they were able to reduce airflow to 30 percent during setback periods, thereby using 70 percent less fuel to heat the air and far less electricity to run the fans.

See the related feature article, "How to Maximize Burner Efficiency. Because natural gas energy costs are a major cost factor for many industrial processes, it makes sense to carefully analyze how the natural gas is being used and whether the system is running at peak efficiency.