Emerson Liebert iCOM, Manual

Page: 32 / 172

Operation
Liebert
®
iCOM
®
for Liebert DSE
™
24
High Pressure Alarm
When the compressor is initially activated, the system will be monitored for a high pressure situation.
When a high pressure situation is detected during the first 10 minutes of operation, the unit will
attempt to correct the problem several times without notification. If the unit is unsuccessful in
correcting the problem, an alarm will occur and the affected compressor will be locked Off. If high
head pressure alarm trips three times in a rolling 12 hour period, the affected compressor will be
locked Off.
After the compressor has been running for 10 minutes, if a high head pressure situation is detected,
an alarm will occur and the affected compressor will be immediately locked Off without the unit
trying to correct the problem.
Once the compressor is locked Off, it will not come back On until main power is reset or until the
HP Alarm Counters (Service Menu, Diagnostics) are reset to 0.
Figure 20 Diagnostics/service mode screen, page 1 of 8
Setting the counter to 0 will auto-reset the alarm without the need of pressing the reset button on the
display. Even if the pressure in the system drops below the alarm point, the compressor will remain
Off until the system is reset.
Advanced DX High Pressure Protection
The goal of the advanced high pressure protection routines are to prevent a high pressure lockout
from occurring. The Liebert iCOM does this by constantly monitoring the condensing pressure. If the
control has determined that pressure is not maintained, the compressor capacity will automatically
adjust to help lower the operating pressure. This built-in intelligence operates the compressor at a
slightly reduced capacity, reducing the chance of a total loss of cooling created by a high-pressure
lockout.
This feature is standard on units equipped with liquid line transducers and the compressor types
listed below.
NOTE
If the unit is equipped with manual reset high head pressure switches, or if the auto reset high
head pressure switches don’t reset, the compressor will not be turned back on, but there will be
a 30-second delay from when the high head pressure situation occurs and when the alarm is
annunciated.
HP Alarm Counters