Vertiv Liebert XD Series, System Design Manual

Page: 99 / 200

5 LIEBERT XDC AND LIEBERT XDP
5.1 Liebert XDC Standard Features
•
Compressors
—Scroll with a suction gas cooled motor, vibration isolators, thermal overloads,
manual reset high-pressure switch and pump down low-pressure switch.
•
Refrigeration System
—Dual refrigeration circuits each including liquid line filter dryers,
refrigerant sight glass with moisture indicator, electronic control valve, adjustable externally
equalized expansion valves and liquid line solenoid valves.
•
Heat Exchanger
—Brazed plate design with interwoven circuiting constructed of stainless steel
plates, copper brazed.
•
Pumps
—Centrifugal type, end suction, canned rotor design.
•
Liebert iCOM
—The Liebert iCOM offers the highest capabilities in unit control, communication
and monitoring of Liebert Precision Cooling units. The Liebert iCOM is a factory-installed
assembly. Operating conditions and status are indicated on the unit display, which is mounted
either on the unit or on the wall, depending on application details (see the Liebert XDC user
manual, SL-16674, available at www.VertivCo.com. The control system also monitors unit
operation and activates an alarm when any of the specified factory preset conditions are
exceeded. The unit includes two temperature-humidity sensors to aid in effective cooling.
•
Liebert Lee-Temp
™
Refrigerant Control Air-Cooled Condenser
—The Liebert Lee-Temp head
pressure control system is designed to maintain proper operating head pressures in outdoor
temperatures down to -30°F (-34.4°C). The condensers utilize head pressure control valves,
extra refrigerant and insulated refrigerant receivers with heater pads. It works by flooding the
condenser coil with liquid refrigerant to a level that balances the system condensing
requirements with the condenser coil surface available to reject the system heat. During the
summer, the system requires the entire condenser coil surface for heat rejection and most of
the refrigerant is stored in a receiver. In the winter, the same amount of heat can be rejected by
only a fraction of the coil surface. As head pressure begins to fall, the control valve restricts the
flow of liquid refrigerant exiting from the condenser. This extra liquid refrigerant reduces the
effective condenser surface area available for heat transfer. The head pressure control valve
also bypasses hot gas into the receiver to warm the liquid and maintain liquid pressure for
proper operation of the expansion valve. Condenser fan controls are either fan cycling on
ambient temperature or constant on.
5.1.1 Liebert XDC Optional Features
•
Water / Glycol Condensers
—A water/glycol floor stand condenser option is available for heat
rejection requirements. The water/glycol floor stand can be installed beneath the Liebert XDC
or nearby.
Vertiv | Liebert® Xtreme Density™ System Design Manual | 99