3.1.1.9 Fan System Controlled by Drives
Return
Supply
air
V.A.V
outlets
Duct
Mains
Pump
Return
Flow
Mains
Fan
Main
B.M.S
Local
D.D.C.
control
Sensors
Fan section
Pressure
control
0-10V
or
0/4-20mA
Control
temperature
0-10V
or
0/4-20mA
Control
temperature
0-10V
or
0/4-20mA
Illustration 10: Fan System Controlled by Drives
3.1.2 Application Examples
The following sections give typical examples of applications.
3.1.2.1 Variable Air Volume
VAV or variable air volume systems, control both the ventilation and temperature to satisfy the requirements of a building. Central
VAV systems are considered to be the most energy efficient method to air condition buildings. By designing central systems instead
of distributed systems, a greater efficiency can be obtained.
The efficiency comes from utilizing larger fans and larger chillers which have much higher efficiencies than small motors and distrib-
uted air-cooled chillers. Savings are also seen from the decreased maintenance requirements.
The VLT Solution
While dampers and IGVs work to maintain a constant pressure in the ductwork, a drive solution saves much more energy and re-
duces the complexity of the installation. Instead of creating an artificial pressure drop or causing a decrease in fan efficiency, the
drive decreases the speed of the fan to provide the flow and pressure required by the system.
Centrifugal devices such as fans behave according to the centrifugal laws. This means that the fans decrease the pressure and flow
they produce as their speed is reduced. Their power consumption is thereby significantly reduced. The PI controller of the drive can
be used to eliminate the need for additional controllers.
AJ363928382091en-000101 / 130R098320 | Danfoss A/S © 2021.04
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VLT® Flow Drive FC 111
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