Application Examples; Variable Air Volume; The Vlt Solution - Danfoss VLT HVAC Basic Drive FC 101 Design Manual

Product Overview

3.1.11 Application Examples

The following sections give typical examples of
applications within HVAC.

3.1.12 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 distributed air-cooled chillers. Savings are also
seen from the decreased maintenance requirements.
Cooling coil
D1
D2
D3
Illustration 3.11 Variable Air Volume
MG18C702
Design Guide

3.1.13 The VLT Solution

While dampers and IGVs work to maintain a constant
pressure in the ductwork, a 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 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 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 VLT
to eliminate the need for additional controllers.
Frequency
Heating coil
converter
Filter
Frequency
converter
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HVAC Basic Drive can be used
Pressure
signal
Supply fan
3
Pressure
transmitter
Flow
Return fan
Flow
3
3
VAV boxes
T
19
3