10
System Troubleshooting
Symptom
Possible Cause
Remedy
High head—low suction
■
Restriction in liquid line or flowrator
■
Remove or replace with proper size flowrator.
High head—high or normal
suction
■
Dirty condenser coil
■
Overcharged
■
Condenser fan not running
■
Clean coil.
■
Correct system charge.
■
Repair or replace condenser fan.
Low head—high suction
■
Incorrect flowrator
■
Defective compressor valves
■
Flowrator not seating properly
■
Replace with correct flowrator.
■
Replace compressor.
■
Check for debris under flowrator or deformed flowrator.
Remove debris or replace flowrator.
Unit will not run.
■
Power off or loose electrical connection
■
Thermostat out of calibration; set too
high
■
Defective contactor
■
Blown fuses or tripped circuit breaker
■
Transformer defective
■
High or low pressure control (optional)
open
■
Compressor overload contacts open
■
Check for unit voltage at contactor in unit.
■
Reset thermostat.
■
Check for 24 volts at contactor coil. Replace if contacts
are open.
■
Replace fuse or reset circuit breaker. Check wiring.
Replace transformer.
■
Reset high pressure control or check unit charge.
High pressure control opens at 610 psig, and low
pressure control opens at 22 psig.
■
Replace compressor.
NOTE:
Wait at least 2 hours for overload to reset.
Condenser fan runs;
compressor does not run.
■
Loose connection
■
Compressor stuck
■
Grounded or open winding
■
Open internal overload
■
Low voltage connection
■
Capacitor weak, open or shorted
■
Check for unit voltage at compressor.
■
Check and tighten all connections.
■
Wait at least 2 hours for overload to reset. If still open,
replace the compressor.
■
At compressor terminals, voltage must be within 10%
of nameplate volts when unit is operating.
■
Check capacitor. Replace if defective.
Low suction—Cool
compressor, iced evaporator
coil
■
Low indoor airflow
■
Increase speed of blower or reduce restriction.
■
Replace air filters.
Compressor short cycles
■
Defective overload protector
■
Unit cycling on low pressure control
■
High pressure switch cuts out
■
Replace overload protector. Check for correct voltage.
■
Check refrigerant charge and/or airflow.
■
Check airflow (indoor and outdoor)
Registers sweat
■
Low airflow
■
Increase speed of blower or reduce restriction.
■
Replace air filters.
High suction pressure
■
Excessive load
■
Defective compressor
■
Reversing valve not seating properly.
■
Recheck load calculation
■
Replace compressor.
■
Replace reversing valve.
Insufficient cooling
■
Improperly sized unit
■
Improper airflow
■
Incorrect refrigerant charge.
■
Incorrect voltage
■
Recalculate load.
■
Check airflow—should be approximately 400 CFM per
ton.
■
Charge per procedure attached to unit service panel.
■
At compressor terminals, voltage must be within 10%
of nameplate volts when unit is operating.
Evaporator coil freezing or
frosting
■
Low airflow
■
Low refrigerant charge
■
Operating unit in cooling mode below
65ºF (18ºC) outdoor temperature
■
Check airflow—should be approximately 400 CFM per
ton.
■
Properly charge unit.
■
Install or check low ambient control—should be open
below 65ºF (18ºC) outdoor temperature.