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Fan Basics

Fan Basics

There are several types of fans for various applications. Out of those, Lau manufactures axial propellers fans as well as forward curved, backward curved and airfoil centrifugal fans.


B-Wheels consist of Backward Inclined (BI), Backward Curved (BC) and Airfoil (AF) wheels.

B-Wheels typically produce static efficiencies ranging from 55% – 85% (AMCA). A performance characteristic of a b-wheel is a non-overloading power curve

B-Wheels are used in housed and plenum (unhoused) applications:

Housed double width, double inlet (DWDI) AF fans produce the highest peak efficiencies and are relatively quiet with some tonality.

Single width, single inlet (SWSI) AF and BC fans are capable of reaching high peak efficiencies and produce moderate sound which can be tonal.

Forward Curved (FC) Wheels

Forward curved (FC) wheels require a scroll housing for ideal performance.

FC wheels typically produce static efficiencies ranging from 50% – 65% (AMCA 210). A performance characteristic of an FC wheel & housing is an overloading power curve. FC wheels produce moderate sound with low tonality.

Propeller Fans

Propeller fans (PF) require a matched orifice for optimal performance.

Propeller fans with a matched orifice typically produce static efficiencies ranging from 40% – 55%. A performance characteristic of a propeller fan is a power curve that’s overloading at shut-off. Propeller fans are generally capable in lower pressure applications.

For more information on fan types, check out the ASHRAE Handbook – HVAC Systems and Equipment and find Fans.