LG RCAW Operation & Maintenance Manual page 70

Trouble Shooting
Alarm
Specific alarms, their recognition method, and their possible causes are listed here. To clear alarm and recover from the
alarm, clear the alarm history after correction of the cause of the alarm.
The emergency trouble means that the emergency switch installed on the right side of the control panel is pushed by
operator. This switch input is normally closed and the trouble means the switch input is opened. When the emergency
switch is opened output power for the output control from the PLC is disconnected. By pulling the emergency switch, the
alarm can be corrected.
5E relay, voltage monitoring relay signals alarm when there is trouble with the power supply. The trouble includes over
voltage, under voltage, reversed phase, phase loss, and voltage unbalance. Please be sure that all fuses for detecting
of power supply are not melted in case of phase loss alarm.
Liquid flow trouble means the absence of water flow or shortage of the water flow under 70% of rated water at default
value. Water pump malfunction and shortage of water volume must be observed concurrently to solve the problem.
Pressure trouble means tripping of high pressure cutout switch or low pressure cutout switch. Both of them are pack-
aged in dual pressure switch. When the problem is encountered, proper amount of the refrigerant inside of the chiller
must be inspected firstly. If there is no problem with the amount of the refrigerant, contaminated heat exchanger can be
a reason. Please consider the operating ambient temperature range of the chiller is from 64.4°F~129.2°F(18°C~54°C).
Oil trouble means oil flow absence from the oil separator to the compressor or low oil level in the oil separator.
This alarm is checked after 120 second after running the compressor.
The delay is adjustable through delay setting of the HMI unit. Shortage of oil must be inspected firstly. When the chiller
runs under low ambient temperature without enough pre-heating, much amount of oil can be remained in evaporator
instead of the oil separator. In this case, oil must be added up to the oil separator.
Low differential pressure between the evaporator and the condenser will not guarantee proper oil circulation, so the dif-
ferential pressure must be inspected through pressure gauge.
M1 and M2 are magnetic contactors for screw compressor. The malfunctions of the magnetic contactors mean OCR trip
by overload condition or problem with the contacts of the magnetic contactors themselves.
INT69 trouble means that the internal protector inside of terminal box of the compressor detect abnormally high temper-
ature on the motor winding or compressor discharge.
There can be two sources for the anti-freezing S/W trouble. Actually, the alarm is recognized by tripping of anti-freezing
switch of low water temperature detected by temperature sensor. In case of the low water temperature, the setting point
for the determination of the alarm can be changed by HMI unit.
When there is mechanically welded contact problem with the magnetic contactors for the compressor, the PLC cannot
stop the compressor and consequently you can encounter this alarm at the case. Therefore, in this case you must turn
off the circuit breaker located before the malfunctioning magnetic contactor.
Fan trouble is similar with the M1 or M2 trouble in the case of the compressor. It means OCR trip by overload condition
or problem with the contacts of the magnetic contactors.
Discharge temp trouble is invoked when the compressor discharge temperature is over 176°F(80°C). This can be
caused by shortage of refrigerant or too high ambient temperature
COMM fault trouble means communication failure between the HMI unit and the PLC, loosed connection is frequently
encountered cause the trouble
70 Chiller Air-cooled Screw