Emerson Liebert iCOM Manual De Usuario

When redundancy configurations are required, the Liebert iCOM unit-to-unit network has built in 

fail-over conditions that require no building management interaction. The first and possibly most 

common failure scenario is a single unit or component failure. In this situation, the Liebert iCOM will 

automatically activate a standby unit in the place of the failed unit.
Unit-to-Unit and sensor failure scenarios have also been programmed into the Liebert iCOM 

controller. For example if the remote sensors fail at the unit level, the unit will continue to operate 

using the other unit's remote sensor values. If all remote sensors fail, then the fan speed will begin to 

operate from the supply sensor. If the supply air sensor fails, then the unit will default to 100% fan 

and cooling capacity. In the event of a unit to unit network switch failure, each unit will operate from 

its sensor network.
If one unit becomes disconnected from the network, the disconnected unit will run independently 

according to the local sensor readings. If U2U address No. 1 becomes disconnected from the group, 

each unit will run independently according to the local sensor readings.

The inlet rack temperature sensors should be placed on a rack that is within the area of influence of 

the connected cooling unit. The following floor plan shows how the sensors should be placed. The 

sensors and units are color matched to show the location of each unit's sensors. This particular floor 

plan shows how the sensors can be interlaced with one another to provide redundancy of the different 

unit's sensors. Remember that the sensor data from each unit is shared at the teamwork level so 

placement of the sensors is flexible with your specific application. So even when one unit fails the 

other units are still able to react based on the failed units sensors.
Each unit can connect up to 10 sensor modules with each module allowing for two temperature probes 

for a total of 20 temperature readings per cooling unit. Each of the two probes allows for 6 feet of 

distance between the temperature probe and the module. This provides the flexibility to either place 

both temperature sensor probes at the top of two different racks or to place one sensor probe in the 

middle of the rack and one at the upper two thirds of the rack. Sensors can be placed in other 

locations like the hot aisle but should be set as a reference sensor and not a controlling sensor. This 

will allow the sensor to be monitored by the Liebert iCOM display and building management system 

but will not affect unit operation. 
The rack sensors that are set to control have the flexibility to be set in different averaging schemes. 

There are three different levels of sensor calculations; at the sensor level, at the unit level and at the 

system level (unit to unit network). At the sensor level, the two probes on each rack sensor can be set 

to average or take the maximum value of the two sensors. The setting at the unit level allows the 

operator to select how many of the controlling sensors are averaged. If the unit has 10 rack sensors 

connected for control, the operator can elect to average 1 through 10 of the sensors. For example, 

selecting 3 sensors to average would use the 3 highest sensor readings out of the 10 possible sensors. 

Even though only three sensors are being used for the average, all 10 are being dynamically 

monitored with Liebert iCOM’s rack sensor scanning routine. This means that the three highest 

sensors today might not be the three highest sensors tomorrow.
The system level calculation provides the same level of flexibility as described above for the unit level 

sensor configuration. All remote sensor values, including values from sensors connected to standby 

units, are shared among units in the group. Providing this level of configuration at the unit and 

system level coupled with the rack sensor scanning allows the units and system to be setup for a 

variety of applications, including no containment, end containment and total containment. In 

addition it also allows Liebert iCOM to adjust airflow and cooling capacity as the environment 

changes or if the heat load shifts, increases or decreases.