Centrifugal exhaust fan specifically designed for moderate size ventilation applications. The fan can be mounted at any angle in any point along the duct work and straight-through air flow design allows easy installation. By using FC type mounting clamps, fan can be easily removed from duct work for service. Fans are constructed in accordance with standard dimensions for spiral duct eliminating the need for transition pieces. Fan motors are capable of operating in air stream temperatures up to 140 degrees F. Motor bearings are a permanently sealed, self lubricating ball type. All fans are 100% speed controllable through a decrease in the voltage by using a solid state or transformer type control. Fan housing shall be constructed of heavy gauge galvanized sheet metal. Fan shall be supplied with externally mounted electrical terminal box with pre-wired terminal strip connections. Capacitor shall be located within electric terminal box. Motorized impeller shall be an external rotor type, class B insulation, enclosed with permanent split capacitor. Motor shall be a permanently sealed self lubricating ball bearing type. Motor shall be equipped with automatic reset thermal overload protection. Motor shall be acceptabel for continuous duty. Fan wheel shall be of the backward inclined centrifugal type with a well designed inlet venturi for maximum performance. Motorized impeller shall be both statically and dynamically balanced as one integral unit to provide for vibration free performance. Impellers shall be molded of high impact polypropylene.