Figure 36 Supply Compensation In Unit View; Figure 37 Supply/Return Compensation - Emerson Liebert iCOM Manual

When supply air compensation has been invoked, it will be indicated on the unit view by a small
downward-pointing arrow. See Figure 36.

Figure 36 Supply Compensation in Unit View

During normal operation, as the rack temperature increases above the fan temperature setpoint, the
fan speed will increase until it reaches 100% speed. 100% fan speed is achieved once the controlling
temperature reaches a value equal to 100% of the fan control band, or S116 Fan Setpoint + 1/2(S150
Fan Deadband) + 1/2(S149 Fan Temp Prop Band).
How many degrees the supply temperature will be lowered while supply compensation is invoked
depends on how many degrees the fan controlling temperature has exceeded the control band
compared to S116 Supply Compensation Value.
Example: With a Fan Setpoint of 70ºF and Proportional band of 10ºF, 0ºF deadband, the fan
speed is 100% when the rack temperature is 75ºF. If S116 Supply Compensation value = 10ºF, the
supply air temperature will lower one degree for every degree the rack temperature increases
outside the fan control band. This means if the air temperature setpoint is 65ºF, and the rack
temperature increase to 77ºF, the supply air temperature will lower to 63ºF.
Return + Supply Compensation: This selection provides the ability to enable both supply and
return compensation settings as described above.

Figure 37 Supply/return compensation

After the blower reaches 100
percent and the temperature
continues to increase, the
supply temperature setpoint will
be decreased proportionally
Blower at 100%
of Capacity
72 73
74
Supply Temperature Setpoint
will be decreased by the Supply
Compensation band when the
fan speed proportional band
has doubled
50%
Compensation
76
Blower Proportional Band
Fan Speed Proportional
Band 8°F (4°C)
47
Operation
Supply
Compensation
in Unit View
Supply
Compensation
Band 8°F (4°C)
100%
Compensation
78
® ®
Liebert iCOM for Liebert DSE
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