Unit installation

Operation
50
11.0 OPERATION
Unit operation is completely automatic. The unit operates in the following sequence:
• Air is drawn into the unit by the fans, which operate continuously.
• The temperature and humidity sensor measures the inlet air, and relays this information to the
control system.
• The air is immediately filtered.
• The air is then conditioned and expelled from the unit.
Figure 45 Sensor location
The control system compares the relayed information with the programmed setpoint and proportional
band values and performs one of the following operations:
• Cooling—Direct expansion mode (DX): The compressor is started and the cold refrigerant flows
through the evaporator, thus cooling the air passing through it. For compressor operation see Lie-
bert iCOM user manual, SL-18835.
• Chilled water mode (CW)—The three-way valve is opened and the chilled water flows through
the coil, thus cooling the air passing through it. For valve operation, see the Liebert iCOM user
manual, SL-18835.
• Reheating—Electrical heating (optional): The heating elements heat the air passing over them
during dehumidifcation.
• Dehumidification (DX mode)— The temperature of the cooling coil is reduced to remove mois-
ture from the air. (Refer also to the Liebert iCOM user manual, SL-18835).
In dehumidification mode, the air after passing over the coil is reheated (if needed) by electrical
heaters to stabilize the initial temperature.
• Humidification (optional)—The humidifier creates steam, which is distributed into the air
stream via the steam distribution pipe. (See also Appendix A - - Humidifier).
NOTE
If, during dehumidification, the ambient temperature drops below a specified level,
dehumidification will stop if necessary. (See the Dehumidification Low Limit section of the
Liebert iCOM user manual, SL-18835).