User manual

Operation
57 Liebert
®
iCOM
®
3.9 Liebert Optimized Aisle Control
The Liebert iCOM Optimized Aisle Control has been developed for Liebert DS
™
, Liebert CW
™
, Liebert
Challenger 3000
™
, Liebert PEX
™
and Liebert HPM
™
units to take advantage of the variable fan speed
(EC or VFD Fans) and variable capacity (Chilled Water, 4-Step and Digital Scroll) components that
are available on these units. This new control scheme uses this variable capacity technology and
applies it to ensure that the inlet air temperature to the server is maintained while providing the
greatest amount of energy savings. Maintaining the rack inlet air temperature ensures that the IT
equipment operates trouble free and keeps the server fans from ramping up from their minimum
speed.
Each Liebert cooling unit is equipped with a Liebert iCOM controller that has the ability to collect
and control a supply (Discharge) air temperature sensor, a return temperature and humidity sensor
and up to 20 rack temperature sensors. The Liebert iCOM Optimized Aisle control utilizes each of
these sensors to determine how to adjust the cooling, heating, humidification and dehumidification
capacity of the unit.
All floor mount cooling units equipped with Liebert iCOM can communicate with each other through
standard Ethernet connectivity. This communication between the units allows coordination of cooling
capacity, zoned air flow distribution, fail over protection and different modes of standby operation. To
reach the full benefit of the Liebert iCOM Optimized Aisle Control, the units must have this network
connected.
Upgrades are available for most Liebert cooling units that are not equipped with the Liebert iCOM
control or with a variable speed fan. Contact Emerson Network Power
®
Liebert Services for additional
information.
3.9.1 Operation
Inlet Rack Temperature Control
The Liebert iCOM Optimized Aisle control monitors the inlet temperature to the racks using up to 20
rack temperature sensors that are connected to a Liebert iCOM control. These inlet rack temperature
sensors are used to control the air flow (fan speed) of each unit. The air flow is increased when the
inlet rack sensors detect a temperature higher than the setpoint and will decrease air flow when the
head load decreases or changes to the application are modified (eg., Containment).
Additional Details of Rack Temperature Operation
Refer to Application and Configuration of Rack Sensors on page 80 for rack sensor setup
details.
• The cooling unit’s fan speed is determined based on the amount of deviation from temperature
setpoint (Proportional) and the length of time the actual temperature has deviated from
temperature setpoint (Integral)
• The fan speed control takes into account the actual temperature as it compares to the
temperature setpoint and will modify how fast the fans can change speed to avoid overshooting
the setpoint.
In addition to the speed filters, the fan speed also has programmed independent acceleration and
deceleration rates
These control tuning parameters allow the fans to speed up quickly to match rapid heat load
changes and react to containment doors being opened and closed while still providing stable
control when the application returns to steady state operation.