IM 861
25
Figure 19: Cooling Trouble Shooting Chart
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
• Failed 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-The high pressure
control opens at 450 PSIG
• Interconnecting low voltage wiring damaged
• Replace thermostat wiring
Condenser fan runs, compressor
• Loose connection
• Check for correct voltage at compressor -
doesn’t
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 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
• Incorrect capillary tubes
• Change coil assembly
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
Low head-high vapor pressures
• Defective Compressor valves
• Replace compressor
• Incorrect capillary tubes
• Replace coil assembly
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
High vapor pressure
• Excessive load
• Recheck load calculation
• Defective compressor
• Replace
Fluctuating head & vapor
• Air or non-condensibles in system
• Recover refrigerant, evacuate & recharge
pressures
Gurgle or pulsing noise at
• Air or non-condensibles in system
• Recover refrigerant, evacuate & recharge
expansion device or liquid line
Circulating air blower & inducer
• Manual reset overtemperature control
• Reset or replace
run continuously,
tripped
compressor will not start
• Wire loose in limit circuit
• Check wiring
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.
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DANGER
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