Liebert Icom User Manual Intelligent Communications Monitoring

Posted : admin On 10/7/2021

Page 39: 6 high temperature, 8 humidifier problem, Infrared humidifiers, Steam generating (canister) humidifiers, High head pressure, High humidity, High humidity and low humidity (simultaneously)

  1. Liebert Icom Manual
  2. Liebert Icom Installer User Guide
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Alarm Descriptions

33

6.1.3 High Head Pressure

Compressor high head is monitored with a pressure switch. One SPDT pressure switch is used for the

compressor in the unit. If head pressure exceeds 360 PSIG, the switch opens the compressor contactor

and sends an input signal to the control. On a self-contained system, the head pressure switch located

at the compressor requires a manual reset and the alarm condition to be acknowledged on the front

display panel. On a split system, the high head pressure condition is acknowledged by pressing the

alarm silence button that will clear the alarm if the high head pressure condition no longer exists. On

Liebert icom control manual

a split system, if the compressor is Off for 1 hour, the control goes into a special “cold start mode.” In

the cold start mode on a call for cooling or dehumidification, the Liquid Line Solenoid Valve (LLSV) is

energized. If the high pressure switch does NOT trip within 10 seconds, the control returns to normal

operation of monitoring the high head pressure switch for three occurrences in a 12-hour period. It is

a rolling timer; after the third high head alarm occurs and is acknowledged by the user, it will lock Off

the compressor. If while in the cold start mode, the high head pressure switch DOES trip within 10

seconds of the activation of the LLSV, the control does not annunciate the alarm. The control will turn

Off the LLSV and delay 10 seconds. The control will permit this occurrence two more times or a total

Liebert Icom Manual

of three times. If on the fourth try the high head pressure switch trips within 10 seconds, the control

will annunciate the alarm, turn Off the LLSV, wait for the user to acknowledge the alarm and hold

the compressor Off for three minutes, which is the normal short cycle control. On the third occur-

rence, the control will lock the compressor Off until the control power is reset.
On air cooled systems, check for power shut Off to the condenser, condenser fans not working, defec-

tive head pressure control valves, closed service valves, dirty condenser coils, and crimped lines. Also,

make sure that when the compressor contactor is energized, the side switch on the contactor closes to

energize the control circuit on the air cooled condenser.
On water/glycol/GLYCOOL systems, check water regulating valves. Verify water/glycol flow (are

pumps operating and service valves open?). Is water tower or drycooler operating? Is the coolant tem-

perature entering the condenser at or below design conditions? Is relay R5 operating during cooling to

turn On the drycooler?

6.1.4 High Humidity

The return air humidity has increased to the High Humidity Alarm setpoint. Is the unit setup for

dehumidification (check DIP switch)? Check for proper setpoints. Does the room have a vapor barrier

to seal it from outdoor humidity? Are doors or windows open to outside air? Run diagnostics to make

sure the cooling system is working properly (the cooling system dehumidifies).

6.1.5 High Humidity and Low Humidity (Simultaneously)

If these two alarms are displayed at the same time, the humidity input signal is lost. Dashes will be

displayed for the humidity reading. The control system will deactivate humidification and dehumidi-

fication. Check for a disconnected cable or a failed sensor.

6.1.6 High Temperature

If the return air temperature has increased to the High Temperature Alarm setpoint, check for proper

setpoints. Is the room load more than the unit can handle (is the unit capacity too small)? Run diag-

Liebert Icom Installer User Guide

nostics to make sure all cooling components are operating (compressor and/or valves).

6.1.7 High Temperature and Low Temperature (Simultaneously)

If these two alarms are displayed at the same time, the temperature input signal is lost (or the

humidity is out of sensor range: 15 to 85% RH). Dashes will be displayed for the temperature reading.

The control system will initiate 100% cooling. Check for a disconnected cable or a failed sensor.

6.1.8 Humidifier Problem

Infrared Humidifiers

This alarm is activated by the high-water float switch in the humidifier pan assembly. The high-

water float switch is normally closed and opens upon alarm condition. Check for drain clog and, if

present, clean drain. Check for float switch stuck high; replace the switch as necessary. Check for

proper operation of the humidifier water makeup valve.

Steam Generating (Canister) Humidifiers

This alarm is activated by a signal from the humidifier control indicating that the canister needs to be

replaced.

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