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VLT
®
6000 HVAC
MG.60.B1.02 - VLT is a registered Danfoss trademark
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Variable Air Volume
VAV or Variable Air Volume systems, are used to
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 distributed air-cooled chillers.
Savings are also seen from the decreased main-
tenance requirements.
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The new standard
While dampers and IGVs work to maintain a constant
pressure in the ductwork, a VLT frequency converter
solution saves much more energy and reduces the
complexity of the installation. Instead of creating an
artificial pressure drop or causing a decrease in fan
efficiency, the VLT frequency converter 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 the fans decrease
the pressure and flow they produce as their speed is
reduced. Their power consumption is thereby
significantly reduced.
The return fan is frequently controlled to maintain a
fixed difference in airflow between the supply and
return. The advanced PID controller of the VLT 6000
HVAC can be used to eliminate the need for addi-
tional controllers.
Pressure
signal
VAV boxes
Flow
Flow
Cooling coil
Heating coil
D1
D2
D3
Filter
Pressure
transmitter
Supply fan
Return fan
T
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