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.
(16 pages)
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