Vertiv Liebert XD Series, System Design Manual

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6 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
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
Table 6.1
Receivers and head pressure kits for Liebert Lee-Temp 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.
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