Emerson Liebert iCOM Manual De Usuario

A variety of chilled water valves and actuators are offered depending on application requirements. 

Floating point and analog actuators are common to most applications.
Floating point actuators are driven through two digital outputs: Open and Close. As default, Liebert 

iCOM determines the valve position by timing how long the open or closed signals have been active 

based on the valve travel time set in the Service menu / Setup submenu. The valve response may be 

improved by implementing a valve feedback signal. See 3.2 - General Chilled Water Operation for 

more information.
Analog driven actuators commonly work off a direct or indirect 0-10 or 2-10 VDC signal. Liebert 

CW181 models and larger units may contain two analog valves; as default, both valves will be 

controlled in parallel for cooling. Other valve staging options are available. See 3.2.3 - Custom Dual 

Chilled Water Valve Staging for more information.
In all applications, the valves open and close according to a call for cooling as shown in Figure 31. 

The chilled water control valve is adjusted proportionally as the temperature control varies the 

requirement for cooling from 0% to 100%.

Two types of fluid economizers are offered, GLYCOOL and Dual-Cool. GLYCOOL models are two-pipe 

systems. This means that two pipes enter the unit and feed the chilled water/free-cooling coil as well 

as the compressor(s) and heat exchanger (eg., Liebert Paradenser

™

, tube-in-tube condenser or brazed 

plate heat exchanger). Dual-Cool units can be either two-pipe or four-pipe systems. A two-pipe unit 

has two fluid lines dedicated to the secondary cooling source, and the compressor(s) heat rejection is 

an air-cooled condenser. Four-pipe Dual-Cool models have two fluid pipes dedicated to chilled 

water/free-cooling and two pipes for the compressor(s) heat exchanger. Each model offers a primary 

DX source and a secondary chilled water or free-cooling coil.