Technical Specifications

Heat Rejection
110
6.6.1 Liebert Drycooler Fan Cycling Control
Available on all sizes of standard sound and Quiet-Line drycoolers. A thermostatic control cycles the
fan on a single-fan drycooler in response to leaving fluid temperatures. Two or more thermostats are
employed on drycoolers with two or more fans to cycle fans or groups of fans in response to leaving
fluid temperatures. The thermostat setpoints are listed on the factory-supplied schematic. They
typically range from 35 to 45°F (2 to 7°C) for GLYCOOL applications and 65 to 75°F (18 to 24°C) for
glycol applications.
6.6.2 Pump Controls
Controls for pump(s) up to 7.5hp are built into the same integral electric panel as the drycooler fan
controls. Pump fuses, overload heaters and flow switch (dual pump control models) are included with
the Liebert pump packages or must be field-supplied for field-supplied pumps.
Dual pump option—Provides controls for primary and standby pump. The flow switch senses loss of
flow and switches to the standby pump for continuous system operation in the event of a pump
failure. An internal switch allows manual selection of the lead/lag pump.
6.7 Typical System configurations
The standard glycol-cooled precision air conditioning system includes these major components:
• indoor air conditioning unit with heat exchangers (refrigerant/glycol)
• glycol regulating valve
• outdoor air cooled drycooler
• glycol pump(s)
• expansion/compression tank
• pump controls
• interconnection piping
• unit interlock control wiring
Figure 110 shows a typical configuration of multiple indoor units and multiple outdoor drycoolers
using a dual pump package and on a common piping loop.
Additional field-supplied components, such as valves, expansion tank, strainers and flow or pressure
switches are also shown in Figure 110. These components are necessary and should be included
when designing a system with one indoor and one outdoor unit on a piping loop or a system using
multiple indoor and outdoor units on a common piping loop. Larger systems may also benefit from an
air separator (not shown). Refer to SL-10080, available at Liebert's Web site, www.liebert.com, for
further details on required components.