LG GEN2 Series Installation And Operation Manual page 57

Troubleshooting – Refrigeration Circuit
Symptom Possible Cause
Insufficient refrigerant charge.
Defective or improperly adjusted
Low
expansion valve.
discharge
pressure
Low suction pressure.
Faulty condenser temperature controls.
(Condensing fan cycle switch).
Thermostat location or controls
malfunction.
Improper refrigerant charge.
Defective high or low pressure control.
Compressor
Poor air distribution.
short cycles
High discharge pressure.
Low airflow at evaporator(s).
Incorrect unit selection (oversized).
Refrigerant leak.
Short cycling.
Compressor
loses oil Refrigerant flood back.
Reheat flush cycle inadequate.
Refrigeration undercharged.
Dirty filter or evaporator coil.
Dirty or clogged condenser coil.
Not enough
cooling Air or other non-condensables in
or lack of system.
cooling
Restriction in suction and liquid line.
Control contacts stuck.
Excessive load.
Liquid line
is frosted
Restriction in liquid line.
or wet
Insufficient evaporator airflow.
Suction line
is frosting
Malfunctioning or defective expansion
valve.
Hot gas bypass valve not functioning
Frost on
properly.
evaporator
Manual hot gas bypass valve closed.
coil (Note:
Low load or airflow.
Normal on
ASHP
units in
heating
mode.)
Always have a completed Pre-Start-Up Checklist and Start-Up Checklist prior to requesting parts or service information.
Corrective Action
Check subcooling, check for leak. Repair leak and add
refrigerant.
Check superheating and adjust thermal expansion valve.
See "low suction pressure".
Check condenser controls and reset to obtain desired
condensing temperature.
Check thermostat, check heat anticipator setting.
Check subcooling, verify superheat.
Check high or low pressure switch.
Check ductwork for recirculating.
See "high discharge pressure".
Check blower operation and airstream restrictions.
Contact factory.
Check system for leaks. Repair leaks and add refrigerant.
Check low pressure control settings.
Check thermal expansion valve setting. Check for
refrigerant overcharge. Check crankcase heater
operation.
Contact factory.
Check subcooling. Adjust charge, if necessary.
Check filter, coil and airflow.
Check coil and airflow.
Check equalized high side pressure with equivalent
outdoor temperature.
Check for restrictions in refrigerant circuit.
Check wiring.
Add more equipment or reduce room load.
Clear restriction upstream of point of frosting.
Check airflow, check filters, check VFD control signal for
proper operation.
Check bulb of thermal expansion valve.
Check valve. If defective, replace.
Open valve.
Increase airflow, check filters.