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5.0 ALARMS
The microprocessor control system will audibly and visually signal all ENABLED Alarms (including
two (2) custom alarms). These special alarms can be chosen from the optional alarm list and/or can
have their own fully custom text. The custom alarm inputs are contact closures wired from terminal
24 through a normally open contact to either 50 (alarm 1), 51 (alarm 2), or 56 (alarm 3). The alarms
can be enabled/disabled (refer to 3.0 - Microprocessor Control) and a time delay of 0-255 seconds
can be set. The alarms can also be programmed to either sound the alarm & activate the common
alarm relay OR to sound the alarm only.
When a new alarm occurs, it is displayed on the screen and the audible alarm is activated. (If commu-
nicating with a Liebert Site Product, the alarm is also transmitted). The message “PRESS ALARM
SILENCE” will prompt the operator to silence the alarm. After the alarm is silenced, the display will
return to the Normal Status Display. Alarms can be reviewed by selecting the “ACTIVE ALARMS”
feature. The alarms can also be silenced through communications with a Liebert Site Products Unit.
Many alarms will reset automatically when the alarm condition is no longer present and only after it
has been acknowledged by being “Silenced.” The exceptions are:
1. Software alarms, i.e., Loss of Power and Short Cycle alarms will reset automatically 30 seconds
and 90 minutes respectively, after being silenced or acknowledged; and
2. Specific alarms monitoring overload or high pressure switches may require a manual reset
depending upon the model.
5.1 Alarms: Definitions and Troubleshooting
The following list provides a definition and troubleshooting suggestions for each type of alarm. Refer
to 8.0 - Troubleshooting for additional details. If you need further assistance, contact your Liebert
supplier. THE CUSTOMER MUST SPECIFY ALARM(S) AT THE TIME OF ORDER. OTHER
DEVICES AND WIRING MAY BE REQUIRED AT THE FACTORY FOR SOME OF THE ALARMS.
5.1.1 Custom Alarms
Custom alarm(s) messages are programmed at the LCD display. The message displayed may be
included in a list of provided alarms or it may be customized text (for up to three alarms). IF CUS-
TOMIZED TEXT IS USED, MAINTENANCE PERSONNEL SHOULD BE INFORMED OF THE
ALARM FUNCTION AND THE REQUIRED ACTION.
5.1.2 High Head Pressure
Compressor head pressure is monitored with a pressure switch. (One SPDT pressure switch is used).
If head pressure exceeds 360 psig, the switch turns off the compressor contactor and sends an input
signal to the control. The condition is acknowledged by pressing the alarm silence button on the wall
box, which will clear if the head pressure is alleviated. If the head pressure alarm has activated three
times, the alarm will lock until the unit is serviced. After the head-pressure problem is fixed, reset the
control by disconnecting power to the evaporator unit.
Air-Cooled Systems
Check for power shut off to the condenser, condenser fans not working, defective head pressure con-
trol valves, dirty condenser coils or crimped lines.
Water/Glycol Systems
Check water regulating valves. Verify water/glycol flow (i.e., pumps operating and service valves
open). Is water tower or drycooler operating? Is the coolant temperature entering the condenser at or
below design conditions? Is AUX relay (terminals 70 & 71) operating during cooling to turn on the
drycooler?