Centrifugal fan are commonly found in commercial heating, airconditioning, and ventilation systems. In this role they serve the same function as a squirrel cage fan as a prime air mover. A centrifugal fan can produce a higher output pressure than a squirrel cage blower and, therefore, is the preferred choice for pumping large positive pressure air distribution systems. These blowers are similar in construction and operation to the squirrel cage units. The impeller is generally a flat plate with four to ten blades arranged in a spoke pattern on one side. The plate has a hub, which mounts the impeller to a shaft. Smaller units will have their impellers mounted directly to the motor shaft. Larger units will carry a drive shaft, which is driven via a v-belt drive.
The housing is normally a welded assembly constructed from heavy gauge sheet metal.
As the impeller rotates, air is drawn into the input and slung outward toward the Outside Diameter (OD) of the impeller through centrifugal action. The air is forced into the plenum and through the output.