Series 2 fans were originally developed for use on textile-type motors, but many manufacturers use these “paddle wheel” shapes for both internal and external motor cooling. The absence of a back plate on these fans permits air flow through the motor rotor in either direction. These fans are particularly adaptable since it is so easy to saw off the blades tips. All fans of this type work by creating a higher pressure at the blade tips than at the hub. The shape of the fan guard or motor housing then determines the path of the higher pressure air. The pressure is typically a few pounds per square foot near the blade tips and varies with the motor speed.
Select the Overall Diameter Range (D) that the fan you are looking for fits into.