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GLYCOOL Systems—Standard and Optional Features
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9.0 GLYCOOL SYSTEMS—STANDARD AND OPTIONAL FEATURES
9.1 GLYCOOL—Self-Contained Models Only
The Liebert GLYCOOL free-cooling system is integrated with a glycol-cooled Liebert Challenger ITR.
At outdoor temperatures below 35°F (1.6°C), the Econ-O-Coil is capable of providing total system
capacity. At outdoor temperatures between 35° and 65°F (1.6° and 18.3°C), the unique modulating
valve permits partial cooling of the space by the Econ-O-Coil with the DX system picking up the rest
of the load. Above 65°F (18.3°C) the unit functions as a glycol unit and all the cooling is accomplished
by the DX system. When cooling is required, the three-way modulating valve and water regulating
valve direct glycol (from the heat rejection loop) to the Econ-O-Coil located upstream of the evaporator
coil, to the condenser, or to both.
The GLYCOOL system contains all the standard features of a glycol-cooled system plus the following.
9.2 GLYCOOL System—Standard Features
9.2.1 Comparative Temperature Monitor
A solid-state temperature monitor compares the room air temperature and entering glycol tempera-
ture. When air temperature is higher than glycol temperature, the monitor communicates to the
microprocessor control that “free-cooling” is available.
9.2.2 Econ-O-Coil
The Econ-O-Coil is strategically located in the return air stream of the environmental control system.
This coil is designed for closed-loop applications using properly treated glycol solutions. Applications
using a cooling tower loop or other open water system must specify a 70/30 Cu-Ni Econ-O-Coil for
improved corrosion resistance.
The air is first filtered before entering the coil and then is either precooled or totally cooled before
entering the refrigeration coil. The glycol flow to the coil is controlled by a pre-piped modulating
three-way valve. When supplied with a 45°F (7.2°C) glycol solution, the coil is sufficiently sized to
offer the identical cooling capacity as is obtained during the refrigeration cycle of the compressor.
9.2.3 GLYCOOL Three-Way Control Valve
The GLYCOOL Three-Way Control Valve opens full anytime the temperature of the glycol solution is
below room temperature, to take full advantage of all possible free cooling. As the outdoor ambient
drops, the three-way control valve modulates the flow to the Econ-O-Coil. It maintains constant tem-
perature in the room and includes operating linkage and electronic motor. Unlike other valves of this
nature, there is no over travel linkage or end switches to be adjusted.
9.2.4 Glycol-Regulating Valve
A head pressure operated glycol regulating valve accurately controls the condensing temperature and
system capacity for various entering glycol temperatures. The valve has three-way action.