Technical Specifications

Heat Rejection
95
6.0 HEAT REJECTION
6.1 Liebert Lee-Temp
™
Refrigerant Control Air-cooled Condensers
The Liebert XDC requires two air-cooled condensers per unit. Each condenser requires one receiver.
6.1.1 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.
6.1.2 Standard Features-All Condensers
Liebert condensers consist of condenser coil(s), housing, propeller fan(s) direct-driven by individual
fan motor(s), electrical controls and mounting legs. Liebert air-cooled condensers provide positive
refrigerant head pressure control to the Precision Cooling indoor unit by adjusting heat rejection
capacity. Various methods are employed to match indoor unit type, minimum outdoor design ambient
and maximum sound requirements.
6.1.3 Condenser Coil
Liebert-manufactured coils are constructed of copper tubes in a staggered tube pattern. Tubes are
expanded into continuous, corrugated aluminum fins. The fins have full-depth fin collars completely
covering the copper tubes, which are connected to heavy wall Type “L” headers. Inlet coil connector
tubes pass through relieved holes in the tube sheet for maximum resistance to piping strain and
vibration. Coils are either single circuit or dual circuit, depending on the application. The hot-gas and
liquid lines are spun shut at the factory and include a factory-installed Schrader valve. Coils are
factory leak-tested at a minimum of 300 psig (2068kPag), dehydrated, then filled and sealed with a
nitrogen holding charge for shipment.
6.1.4 Housing
The condenser housing is fabricated from bright aluminum sheet and divided into individual fan
sections by full width baffles. Structural support members, including coil support frame, motor and
drive support, are galvanized steel for strength and corrosion resistance. Aluminum legs are provided
for mounting unit for vertical discharge and have rigging holes for hoisting the unit into position. The
unit's electrical panel is inside an integral NEMA 3R weatherproof section of the housing.
Table 33 Receivers and head pressure kits for Liebert Lee-Temp condensers
Outdoor Ambient
°F (°C)
Condenser
Model 50/60Hz
Condenser
Qty
Receiver
Part #
Receiver
Qty
Head
Pressure Kit
Head
Pressure
Kit Qty
-30 to 100 (-34 to 38) DCSL415 2 185010G2
1
/G4
2
2 179711G1 2
-30 to 105 (-34 to 41) DCSL616 2 179713G1
1
/G2
2
1 179711G2 2
35 to 105 (2 to 41) DCSL616 2 181610G2
1
/G4
2
2 179711G1 2
1. 120V heater
2. 230V heater