Custom Alarms; High Head Pressure; High Humidity; High Humidity And Low Humidity (Simultaneously) - Liebert Himod Operation & Maintenance Manual

5.1.3

Custom Alarms

Custom alarm messages are programmed at the LCD display. The alarms may be specified by the
customer at the time of order. Additional devices and wiring may be required at the factory or by oth-
ers. The message displayed may be included in this alphabetical list of alarms, or it may be custom-
ized text (for up to 2 alarms). If customized text is used, customer maintenance personnel should be
informed of the alarm function and corrective action required.
5.1.4

High Head Pressure

Compressor high head 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. On a split system, the condition is acknowledged by pressing the alarm silence
button that will clear the alarm if the high head pressure condition no longer exists. On a self-con-
tained 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. In the event the high head pressure
alarm has been activated three times on either type of system, compressor operation will be locked off
until the unit is serviced. "High Head Lockout" will be displayed at the front panel display. After the
head pressure problem is repaired, cycling the main power to the evaporator unit will reset the con-
trol.
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?
5.1.5

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).
5.1.6

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.
5.1.7

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-
nostics to make sure all cooling components are operating (compressor and/or valves).
5.1.8

High Temperature and Low Temperature (simultaneously)

If these two alarms are displayed at the same time, the temperature input signal is lost (or the humid-
ity 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.
5.1.9

Humidifier Problem

Steam Generating (canister) Humidifiers
This alarm is activated by a signal from the humidifier control indicating that the canister needs to be
replaced.
Alarm Descriptions 35