Operation
Liebert
®
iCOM
®
for Liebert DSE
™
44
3.6.1 Supply Temperature Control
The Liebert iCOM monitors and adjusts the supply (discharge) air temperature of the unit to provide
a consistent under-floor air temperature by adjusting the compressor capacity or chilled water valve
position. The supply temperature control operates the cooling capacity independently of the air flow
that is controlled from the inlet rack temperature. The only time that the chilled water valve or the
compressor will deviate from the supply temperature control is when temperature compensation has
been activated.
The supply sensor should be located 5-15 ft. (1.5-4.5m) from the unit to provide an accurate reading
for the control. A 50 ft. (15m) extension cable is available from Emerson if the sensor must be farther
than 15 ft. (4.5m) from the Liebert iCOM (P/N 186978G5).
Additional Details of Supply Operation
• The valve(s) / compressor(s) position is 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 valve(s) / compressor(s) also have programmed independent filters that will slow the rate of
change as the actual temperature approaches temperature setpoint.
Temperature Compensation
Temperature compensation links between the cold aisle temperatures, cooling capacity and air flow.
Changes that could invoke temperature compensation would be the removal of floor tiles in non-cold
aisle areas, incorrect supply temperature setpoint, unit failure in another zone or heat load changes
greater than expected heat load changes in rack equipment. As a further protection, the temperature
compensation routine also ties into the cascade /standby operation when Teamwork Mode 3 is
selected.
There are three selectable compensation routines to choose from: Return, Supply or Supply.
Return Compensation
: This temperature compensation monitors the return air condition and
automatically adjusts the supply air setpoint if return temperatures become too cold. Return
compensation can be enabled in all fan and temperature control sensor configurations, with the
exception of fan and cooling set for return air control (Enable Return Compensation falls back to
“No”). With return air compensation enabled, S103 “Temperature Setpoint” remains unchanged as
long as the air temperature is above S114 “Return Compensation Setpoint.”
If the return air temperature falls below S114 “Return Compensation Setpoint,” S103 “Temperature
Setpoint” will be increased. The calculated compensation setpoint is displayed as the left hand value
(Act) of line S103 (see
). Return compensation is also indicated from the unit view as shown
Figure 31 Return Compensation Setpoint in Service Menu
Calculated Return
Compensation
Setpoint
Summary of Contents for Liebert iCOM
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