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TRG-TRC013-EN 67
adjustable-frequency drive (AFD)
See
variable-speed drive.
airfoil (AF) A type of centrifugal fan that is similar to the backward inclined
fan, with the exception that the fan blades are in the shape of an airfoil, like an
airplane wing.
AMCA Air Movement and Control Association
ARI Air-Conditioning & Refrigeration Institute
ASHRAE American Society of Heating, Refrigerating and Air-Conditioning
Engineers
attenuation The process in which sound energy is absorbed or otherwise
diminished in intensity.
axial fan A type of fan where the air passes straight through the fan, parallel to
the shaft.
backward curved (BC) A type of centrifugal fan with blades that are curved
away from the direction of wheel rotation.
backward inclined (BI) A type of centrifugal fan with flat blades that are
slanted away from the direction of wheel rotation.
BAS Building automation system
blocked-tight static pressure The point on the fan performance curve where
there is no airflow: only static pressure is being generated by the fan.
centrifugal fan A type of fan where the air enters the center of the fan from the
side and follows a radial path through the fan wheel.
constant-volume system A type of air conditioning system that varies the
temperature of a constant volume of air supplied to meet the changing load
conditions of the space.
DDC Direct digital control: a method of unit control using a microprocessor
that enables digital communication between the unit controller and a central
building automation system.
discharge damper A device used to control the capacity of a fan by creating a
static-pressure drop in the system, just downstream of the fan.
dynamometer A device used to measure the power applied to the fan shaft.
VAV system modulation curve A curve that illustrates the VAV system fan’s
static-pressure requirement over the range of airflows.
fan performance curve A plot of a specific fan’s airflow capacity at a given
speed (rpm) versus the pressure it generates.
Glossary