Danfoss VLT HVAC Basic Drive FC 101 Design Manual page 20

Product Overview
Primary pumps
2 2
Ask for The Drive to...Improve your primary pumping in primary/secondary pumping systems, MN60D.
Secondary pumps
Ask for The Drive to...Improve your secondary pumping in primary/secondary pumping systems, MN60E.
2.6.12 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, 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.
2.6.13 The VLT Solution
While dampers and IGVs work to maintain a constant pressure in the ductwork, an adjustable frequency drive 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 adjustable frequency 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 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
D1
D3
Figure 2.11 Variable Air Volume
18
Design Guide
®
HVAC Basic Drive can be used to eliminate the need for additional controllers.
Cooling coil
Heating coil
D2
Danfoss A/S © Rev. 2014-01-14 All rights reserved.
Pressure
signal
Frequency
converter
Filter
Supply fan
3
Frequency
converter
Return fan
3
VAV boxes
Pressure
transmitter
Flow
Flow
T
MG18C522