Emerson ITR Manuel D’Utilisation

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.

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.

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.

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.

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.