Air Volume Control, What is air volume control, How to control air volume
air volume control speaks to what is air volume control and how to control air volume describes how the control of the air volume delivered by a fan may be accomplished.
Variable speed motor control.
Outlet damper control.
Variable inlet vane control.
Fan drive change.
Fan Control Reviews
Use of variable speed motor to control fan capacity is the most efficient means of control and the best from the standpoint of sound level. It is however the most expensive.
Use of outlet dampers with a constant speed motor is the least expensive method but also the least efficient.
Variable inlet vanes may be used to adjust the fan air volume delivery over a wide range. This method controls the amount of air spin at the fan inlet, thus controlling the static pressure and horsepower requirements at a given fan speed.
Explain Fan Control Theory
There are engineering graphs available which compare variable inlet vane control, outlet damper and speed control as each affects fan performance. The horsepower curves indicate the power required at various fan settings, damper positions and fan speeds.
Fan drive changes will set fan capacity. The larger the outside diameter of the motor pulley, the faster the fan speed. The faster the fans speed the more supply air. The inverse is also true.
The smaller the outside diameter of the fan pulley, the faster the fan speed. The inverse is also true.
The limiting factor to fan speed increase is the drive motor amperage rating. The faster the fan speed the more current draw there is.
Tubeaxial and vaneaxial fans are often equipped with adjustable blades for matching the fan to system requirements.
Propeller fans may be speed controlled or blade adjustable.
Fans may be arranged in series or in parallel to provide for operating conditions not met by the use of a single fan.
Explain fan control presents possible series applications which are:
Fan Control Reviews
A recirculating fan increases supply air to a space without having to increase the primary air.
A booster fan is used to step up the static pressure in an air system in order to serve a remote area which has intermittent load requirements. When the area is occupied the fan may be energized.
A return fan differs from supply fans in that they are installed on the return air ductwork usually in close proximity to the supply fan. They are usually used to facilitate the controlling of the mixture of return air and outside air and to avoid excessive room static pressure.
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