Operation
Liebert
®
iCOM
®
for Liebert DSE
™
26
3.2
Temperature Control
The Liebert DSE must be operated in a conditioned space within the operating envelope ASHRAE
recommends for data centers: Maximum return air temperature of 105°F (40°C). The recommended
minimum return air temperature setpoint for the Liebert DSE is 75°F (24°C). Operating outside this
envelope can decrease equipment reliability.
Refer to ASHRAE’s publication, “Thermal Guidelines for Data Processing Environments.”
The Temperature Control parameters are in the Service menu under the Setpoints submenu. The
Temperature Setpoint parameter is in both the User Menu and Service Menu under Setpoints.
The Liebert iCOM has two Temperature Control Types:
• Proportional
• PI
Each control type affects the timing and intensity of the cooling/heating operations. The Control Type
parameter is in the Service menu under Setpoints.
Proportional
—If proportional control is selected, the percent cooling/heating requirement is
determined by the difference between the air temperature sensor reading and the temperature
setpoint. The Temperature Proportional Band is a user-defined range that is divided into two equal
parts for cooling and heating. Figure 21 illustrates how the temperature proportional band is evenly
divided on either side of the temperature setpoint.
Figure 21 Temperature proportional band
The Temperature Setpoint is between these two equal parts. As the air temperature rises above the
temperature setpoint, the percent cooling required increases proportionally (from 0 to 100%) over half
the programmable temperature proportional band.
The percent heating requirement (0 to -100%) is determined the same way when the air temperature
falls below the setpoint. The humidifying/dehumidifying operations are controlled in the same
manner as the cooling/heating operations; however, the humidity sensors, setpoints and proportional
bands are utilized.
When the air temperature reaches the end of the proportional band, either 100% or -100%, full cooling
or full heating capacity is provided. No operation is performed when a 0% call is calculated or the
temperature is within the deadband. The control varies the call for cooling and heating in 1%
increments as the air temperature moves through the proportional band halves.
PI
—PI Control functions with all type of compressors and valves. If PI Control is selected, the percent
cooling/heating requirement is calculated by combining two methods, proportional and integral. The
proportional term is calculated in a manner similar to the previously described Proportional control.
0%
Setpoint
0%
Cooling
+ Temp
+ 100%
Cooling
½ Proportional Band
Dead-
band
- Temp
Heating
- 100%
Heating
½ Proportional Band
Cooling
Heating
- Temp
+ Temp
0%
Setpoint
+ 100%
Cooling
- 100 %
Heating
½ Proportional Band
½ Proportional Band
With Deadband
Without Deadband
Summary of Contents for Liebert iCOM
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