Brochures and Data Sheets

9
Energy Ef cient Fan Selections
Variable Speed Drive (VSD)
Fan Motor
Liebert
®
DS™ models with
digital scroll are available with
an optional variable speed drive
(VSD) on the fan motor used to
drive the centrifugal blowers,
matching the motor speed to
the room cooling requirements.
This feature allows the unit to
use far less motor energy to
move room air. The VSD drive is
controlled by the Liebert iCOM
control system to match the
speed of the blower with the
compressor load consequently
the load in the room. This
option eliminates excessive
energy use due to an oversized
design or changing room
conditions.
The downflow floormount Liebert DS models, larger than 12 tons, are
now available with energy efficient EC Plug Fans.
These energy efficient fans add to the superior efficiency already
achieved by the use of a traditional variable speed drive system. In fact,
many utility companies offer a rebate for using these energy efficient
options – check with your local utility for details.
The Liebert DS with EC Plug Fan
delivers energy ef ciency gains via
the fan system. These electrically
commutated fans are a backward
curved motorized impeller powered
by a direct drive DC Motor with
integrated AC-DC conversion.
This design uses less energy than
standard centrifugal blowers by
lowering motor kW. The EC Plug Fan
uses 10-30% less energy on average
than standard AC motors.
The EC Plug Fan is located in the area
beneath the raised  oor or within the
unit. Superior energy savings can be
realized with the fans located beneath
the raised  oor. Placing the fan in
the raised  oor space, is 30 percent
more energy ef cient than centrifugal
blowers. The EC Plug Fan also provides
greater energy savings than variable
speed drives.