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