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4gd5A type of centrifugal fan with blades curved in the direction of wheel rotation.
A device used to control the capacity of a fan by “preswirling” the air in the direction of fan wheel rotation before it enters the wheel, lessening its ability to “bite” the air and reducing its airflow capacity.
A device used to measure small pressures within a duct system.
An optimized method of VAV system static- pressure control that uses the benefits of DDC control to continuously reset the
btt plug fan.
A type of centrifugal fan; it consists of an unhoused fan wheel with airfoil fan blades and an inlet cone that pressurizes the plenum surrounding the fan, allowing the air to discharge in multiple directions.
“riding the fan curve” K –t sx
static pressure and “ride” up and down its performance curve.
A type of axial fan that is well suited for high volumes of air, but which has little or no
tnbdob Sheet Metal and Air Conditioning Contractors’ National Association
A device installed in an air duct system to control discharge air
noise.
The percentage of input power that is realized as useful work in terms of static energy (pressure).
Pressure due to the perpendicular outward “push” of the air against the duct walls.
A condition of unstable fan operation where the air alternately flows backward and forward through the fan wheel, generating noise and vibration.
Turbulence due to fan inlet and outlet restrictions, where the air is not allowed to establish a uniform velocity profile, influencing fan performance.
A curve representing the pressure that the system (including the supply ductwork, duct fittings, terminal units, supply diffusers, return grilles, coils, filters, dampers, etc.) creates over a range of airflows.
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