Boiler Fans

Excess air is the amount of air fed to the boiler burner over and above the amount needed to burn the fuel completely. Excess air makes for safer and more reliable boiler operation because it is impractical to control the precise amount of air reaching the burner. Control valves and pressure regulators cannot control gas flow perfectly. Moreover, a constant gas volume does not guarantee a constant number of air molecules reaching the burner, as changes in temperature and pressure also have an influence.

However, excess air also causes heat loss and consequently reduced efficiency. With increased excess air, the amount of usable energy produced by the burner will remain constant, while the mass of air going through the boiler and exhaust temperatures increase. This increase represents wasted fuel energy. The amount of excess air needed depends on boiler design factors, including the burner that is used.

The fan also provides the air velocity that the burner needs to provide turbulence for the proper mixing of air and fuel. Without enough velocity, higher volumes of excess air will be required.


Due to our continued efforts to improve product design and performance, CFW reserves the right to alter any product details specified here without notice.