27
WARNING

!

XX. TROUBLE SHOOTING CHART

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 Check for correct voltage at compressor contactor in control
box
Thermostat out of calibration-set too high Reset
Defective contactor Check for 24 volts at contactor coil - replace if contacts are
open
Blown fuses Replace fuses
Transformer defective Check wiring-replace transformer
High pressure control open (if provided) Reset-also see high head pressure remedy-
Interconnecting low voltage wiring damaged Replace thermostat wiring
Condenser fan runs, compressor Run capacitor defective (single phase only) Replace
doesn’t Loose connection Check for correct voltage at compressor -
check & tighten all connections
Compressor stuck, grounded or open motor winding Wait at least 2 hours for overload to reset.
open internal overload. If still open, replace the compressor.
Low voltage condition At compressor terminals, voltage must be within 10% of rating
plate volts when unit is operating.
Insufficient cooling Improperly sized unit Recalculate load
Improper airflow Check - should be approximately 400 CFM [188.78 L/s] per ton.
Incorrect refrigerant charge Charge per procedure attached to unit service panel.
Air, non-condensibles or moisture in system Recover refrigerant, evacuate & recharge, add filter drier
Incorrect voltage At compressor terminals, voltage must be within 10% of rating
plate volts when unit is operating.
Compressor short cycles Incorrect voltage At compressor terminals, voltage must be ± 10% of
nameplate marking when unit is operating.
Defective overload protector Replace - check for correct voltage
Refrigerant undercharge Add refrigerant
Registers sweat Low evaporator airflow Increase speed of blower or reduce restriction - replace air
filter
High head-low vapor pressures Restriction in liquid line, expansion device or filter drier Remove or replace defective component
Flow check piston size too small Change to correct size piston
Incorrect capillary tubes Change coil assembly
TXV does not open Replace TXV
High head-high or normal vapor Dirty condenser coil Clean coil
pressure - Cooling mode Refrigerant overcharge Correct system charge
Condenser fan not running Repair or replace
Air or non-condensibles in system Recover refrigerant, evacuate & recharge
High head-high or normal vapor Low air flow - condenser coil Check filters - correct to speed
pressure - Heating mode Refrigerant overcharge Correct system charge
Air or non-condensibles in system Recover refrigerant, evacuate & recharge
Dirty condenser coil Check filter - clean coil
Low head-high vapor pressures Defective Compressor valves Replace compressor
Low vapor - cool compressor - Low evaporator airflow Increase speed of blower or reduce restriction - replace air
iced evaporator coil filter
Operating below 65°F outdoors Add Low Ambient Kit
Moisture in system Recover refrigerant - evacuate & recharge - add filter drier
TXV limiting refrigerant flow Replace TXV
High vapor pressure Excessive load Recheck load calculation
Defective compressor Replace
Fluctuating head & vapor TXV hunting Check TXV bulb clamp - check air distribution on coil - replace
pressures TXV
Air or non-condensibles in system Recover refrigerant, evacuate & recharge
Gurgle or pulsing noise at Air or non-condensibles in system Recover refrigerant, evacuate & recharge
expansion device or liquid line