Emerson Liebert DSE 80-150kW White Paper
A Product Brief from the Experts
in Business-Critical Continuity
Liebert® DSE™ with EconoPhase™:
Highest Efciency DX Cooling with pumped refrigerant economizer
™
Introducing the Liebert® DSE™ from
Emerson Network Power
In today’s data center, minimizing annual energy usage
while maintaining reliability is increasingly important. While
chilled-water loops operating at elevated temperatures
supported by water-side economizers have helped to
decrease energy usage, new innovations are changing how
the data center industry thinks about direct expansion (DX)
cooling infrastructures with respect to efciency, scalability
and reliability.
One such next generation DX system, the Liebert DSE
from Emerson Network Power, provides the following
key benets:
Industry-leading energy efciency among
DX systems
Hassle-free economization with Liebert EconoPhase™
Precise control and enhanced efciency through
intelligent controls
This product brief will provide a thorough overview of
the Liebert DSE system and compare its unique design to
comparable DX and chilled-water cooling solutions you
may be considering for your data center. It also provides a
detailed explanation of the Liebert EconoPhase pumped
refrigerant economizer solution and share specic examples
for how cooling efciency can be maximized intelligently in
accordance with your data center’s ambient climate.
The Liebert DSE direct expansion cooling system comprises
four primary components: the Liebert DSE indoor computer
room air conditioning (CRAC) unit, the Liebert MC™
micro-channel outdoor condenser, the Liebert EconoPhase
pumped refrigerant economizer, and Liebert iCOM™
thermal system controls. The components operate in
harmony to provide the industry’s most energy efcient
operation for a room-based cooling system.
It is important to note that the Liebert DSE is a
complete, integrated system— not a collection
of disparate components.
Uncompromising reliability and 24/7 support
Liebert iCOM
Thermal System Controls
Liebert EconoPhase: First ever
pumped refrigerant economizer
Liebert MC: Intelligent, high
efficiency condensers
Liebert DSE Indoor Unit: Next
generation data center cooling system
The Liebert DSE direct expansion cooling system comprises four primary components: the Liebert DSE indoor computer room air
conditioning (CRAC) unit, the Liebert MC micro-channel outdoor condenser, the Liebert EconoPhase pumped refrigerant economizer
and Liebert iCOM control with thermal system manager.
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Indoor CRAC Unit Designed with
State-of-the-art Technologies
The Liebert® DSE™ indoor unit (DA080, DA085, DA125
or DA150) is equipped with several high-technology
components that are designed and controlled to work
together to provide a highly efcient and reliable DX system.
Key technologies serve the following functions to enhance
energy efciency and performance:
Digital scroll compressors match cooling to
IT load
Staged evaporator coil reduces compressor power and
optimizes economizer performance
Electronic expansion valve enables part-load and low
ambient efciency
Electronically commutated (EC) plug fans match
airow to server needs
To maximize efciency and control at full and partial
loads, the Liebert DSE is equipped with variable capacity
digital scroll compressor technology and direct-drive,
variable-speed EC fans, which are modulated to respond
to and match changes in room load. Varying the capacity
of the compressors enables them to run at a more efcient
operating point than at full capacity. A staged evaporator
coil inside of the unit enables each refrigerant circuit to
operate over large coil surface area, increasing system
efciency. Alternative coil lacing designs that circulate
refrigerant through only one coil slab can result in air passing
through dormant coils, resulting in lower circuit efciency and
uneven air distribution across the coils.
The CRAC’s variable-speed, direct-drive EC fans enable
air volume to be precisely adjusted to match the needs
of the server load. The Liebert DSE’s indoor unit also is
equipped with electronic expansion valves, which enable
compressors to modulate to a lower head pressure than
traditional mechanical expansion valves (TXVs), resulting in
lower operating costs during mild temperatures.
a.
b.
Digital scroll compressors (a) and EC plug fans (b) optimize
the energy efciency of the Liebert DSE by matching cooling
and airow to the demands of the environment.
Highly efficient Micro-Channel
Condenser Design
The Liebert® MC™ condenser integrated into the Liebert
DSE system enables the system to achieve higher efciency,
reduced sound levels, reduced refrigerant charge and an
overall decreased footprint. As shown in Figure 1, microchannel condensers such as those found in the Liebert
DSE system are smaller, lighter (up to 40 percent) and
can require signicantly less refrigerant charge (nearly 73
percent) than a traditional n/tube design. This results in a
greener design, using less refrigerant and providing a more
favorable LEED calculation for refrigerant use.
Because the Liebert MC condenser is equipped with a coil
that is only about one 1 inch thick, the condenser is able
to achieve lower pressure drop on the air side, resulting in
reduced fan power. Micro-channel condenser coils allow
for the same heat transfer within a smaller footprint,
providing efciency gains as much as 52 percent compared
to traditional n/tube condensers. Even higher efciency
levels can be realized during low load or lower ambient
temperatures, when the fan speed can be reduced, utilizing
the condensers’ variable speed fans controlled by Liebert
iCOM™ controls.
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The Liebert® MC™ condenser offers other benets beyond
the intrinsic efciency gains.The micro-channel coil design
eliminates the need for copper/aluminum junctions,
improving the condenser’s resistance to corrosion and
extending the life of key internal components. And the
condenser’s optimized fan blade design signicantly
reduces fan noise at full load - lower operating speeds can
result in even lower sound levels.
Hassle-free Economization with
Liebert EconoPhase™ Pumped
Refrigerant Economizer
In addition to the aforementioned components, the
integrated Liebert EconoPhase pumped refrigerant
economizer – the industry’s rst – is a key component to
maximizing the Liebert DSE™ system’s efciency during
lower outdoor ambient conditions. The Liebert EconoPhase
economizer is unique from other systems particularly
because it is designed to operate without consuming
water, eliminating the need for expensive water treatment
systems and removing the risk of water leaks by not
introducing water into the data center environment. The
Liebert EconoPhase also eliminates the risk of outside
air contamination and does not require maintenance
associated with air-economizers such as damper and
louver maintenance.
Changeover between compressor mode and refrigerant
economizer mode is almost instantaneous, whereas
traditional economizer systems typically operate in
economizer mode only when the economizer season is
stable—not changing back-and-forth during the night, for
example. The Liebert EconoPhase solution is equipped
with variable speed pumps controlled to run at the most
efcient levels according to heat loads and ambient
outdoor temperatures, providing maximum economization
with minimum pump power consumption.
The Liebert EconoPhase is also unique in that it is designed
with reliability in mind. The Liebert iCOM™ control
monitors pump operation to ensure that the pumps do
not cavitate - improving system reliability and service life.
If free-cooling mode is temporarily disrupted, reliability
is maintained by switching to DX operation without
interruption. If a Liebert EconoPhase pump needs to be
serviced, it can be isolated from the system and replaced
without loss of mechanical cooling.
Fin/Tube Liebert MC +/-
Efficiency (COP) 31 47 +52%
Sound Power (dBA) 77.3 73 -4.3 dBA
Refrigerant Charge (lb) 22 6 -73%
Footprint (ft2) 39.8 33.6 -15%
Weight (lb) 670 400 -40%
Figure 1: Breakdown of typical benets offered by the Liebert MC’s micro-channel condenser design, compared to a traditional
n/tube design found in most DX cooling systems.
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