60
WARNING:
Disconnect all power to unit before servicing. Contactor may break only one side.
Failure to shut off power can cause electrical shock resulting in personal injury or death.
SYMPTOM
POSSIBLE CAUSE
REMEDY
Unit will not run
• Power off or loose electrical connection.
• Thermostat out of calibration – set too high.
• Thermostat set too high.
•
Unit in active compressor protection
lockout mode.
• Defective control board.
• Blown fuses/tripped breaker.
• Transformer defective.
• High-pressure control lock-out.
• Low-pressure control lock-out
• Miswiring of communications (communication
light on continuously).
• Check for correct voltage at line voltage connections in
condensing unit.
• Reset – Power cycle high and low voltage to outdoor
•
unit.
• Check thermostat calibration setting.
• Check control board diagnostic codes.
• Replace fuses/reset breaker.
• Check transformer and replace if bad.
• Check wiring. Replace transformer.
• Reset by cycling power to unit. Also see high head
pressure and low suction pressure remedies.
• Check for refrigerant leaks.
• Check communication wiring.
Outdoor fan runs,
compressor doesn't
• Loose connection.
• Communication cable disconnected or failed.
• Compressor stuck, grounded or open motor
winding, open internal overload.
• Low-voltage condition.
• Check for correct voltage at filter and inverter. Check
and tighten all connections.
• Check control board diagnostic codes.
• Replace.
Insufficient cooling
• Improperly sized unit.
• Improper indoor airflow.
• Incorrect refrigerant charge.
• Air, noncondensibles, or moisture in system.
• Restricted refrigerant circuit.
• Recalculate load.
• Check airflow. Should be approximately 400 CFM per
ton.
• Charge per procedure attached to unit service panel.
• Recover refrigerant. Evacuate and recharge.
•
Replace filter drier.
Compressor short
cycles
• Incorrect voltage.
• Improperly sized unit.
• Refrigerant undercharge or overcharge
(LPC or HPC cycling)
• At inverter input terminals, voltage must be between
187-252VAC when unit is operating.
• Adjust refrigerant charge per charging chart.
Registers sweat
• Low indoor airflow.
• Increase speed of blower or reduce restriction.
•
Replace air filter.
High head, low
suction pressures
• Restriction in liquid line, expansion device, or
filter drier.
• Stuck EXV.
• Remove or replace defective component.
• Verify EXV operation.
High head, high
or normal suction
pressure – Cooling
mode
• Dirty outdoor coil.
• Refrigerant overcharge.
• Outdoor fan not running.
• Air or noncondensibles in system.
• Clean coil.
• Correct system charge.
• Repair or replace.
• Recover refrigerant. Evacuate and recharge.
Low head, high
suction pressures
• EXV in bypass mode.
• Bad compressor.
• Verify thermostat connections at EXV control.
• Verify thermistor and pressure transducer connection
and operation.
• Replace compressor.
Low suction pressure,
cool compressor, iced
indoor coil
• Low indoor airflow.
• Operating below 55°F outdoors.
• Moisture in system.
• Low ambient cooling not operating (coil or
ambient thermistor failure).
• Increase speed of blower or reduce restriction.
Replace air filter.
• Recover refrigerant. Evacuate and recharge. Replace
filter drier.
High suction pressure • Excessive load.
• Defective compressor.
• Recheck load calculation.
• Replace compressor.
Fluctuating head and
suction pressures
• EXV hunting.
• Air or noncondensibles in system.
• Check thermistor to vapor line connection. Check air
distribution on coil.
• Check suction thermistor and pressure transducer
operation.
• Recover refrigerant. Evacuate and recharge.
• Remove & confirm EXV movement. Clean EXV inside
with nitrogen to remove any debris then reinstall.
Gurgle or pulsing
noise at expansion
device or liquid line
• Air or noncondensibles in system.
• Undercharged system.
• Recover refrigerant. Evacuate and recharge.
• Check refrigerant charge against charge chart.
9.8 General Troubleshooting Guide
9.0 DIAGNOSTICS & TROUBLESHOOTING
Diagnostics
