Fans - Common Terms and Definitions
bhp (brake horsepower)
The horsepower used by the fan.
cfm (cubic feet per minute)
The volume of air moved per minute. If prefixed with an S, means standard or an A means actual.
fpm (feet per minute)
The velocity of the airstream.
Free Delivery The condition under which a fan operates when no static pressure or resistance is present.
hp (horsepower)
The actual rated output of the fan motor used.
ME (mechanical efficiency)
The ratio of power output to power input.
rpm (revolutions per minute)
The number of times the fan shaft rotates per minute.
Standard Air Dry air which weights .075 pounds per cubic foot at 70 degrees F. with a barometric pressure of 29.92 inches of mercury.
SP (static pressure)
A measure of the force exerted by the fan in moving air through any air handling system.
VP (velocity pressure)
The pressure corresponding to the average velocity determined from the volume of air moving through any air handling system.
TP (total pressure)
The sum of the static pressure (SP) and the velocity pressure (VP) at any given point in the air handling system.
psig pounds per square inch gauge.
psia pounds per square inch absolute.
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