A “right-sized” fan should compensate for performance deficiencies that can occur as a result of cooling system design.
Fans typically are tested and rated in prescribed test configurations defined by the Air Movement and Control Association (AMCA). These standardized procedures and ratings allow system designers to make realistic choices among various manufacturers. However, beyond the routine system resistance calculations, the location of some common components and their proximity to the fan inlet or outlet can create additional immeasurable losses commonly called “system effects.” If these losses are not eliminated or minimized, the fan speed and horsepower will need to be increased to compensate for the resulting performance deficiencies. Understanding some of the common causes for these losses can help engineers more accurately size and select fans, resulting in more efficient and predictable air-handling systems.