Trouble Shooting Chart - McQuay Maverick I MPS006AY Installation And Maintenance Manual

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
Unit will not run
Condenser fan runs, compressor
doesn't
Insufficient cooling
Compressor short cycles
Registers sweat
High head-low vapor pressures
High head-high or normal vapor
pressure - Cooling mode
Low head-high vapor pressures
Low vapor - cool compressor -
iced evaporator coil
High vapor pressure
Fluctuating head & vapor
pressures
Gurgle or pulsing noise at
expansion device or liquid line
IM 865

TROUBLE SHOOTING CHART

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POSSIBLE CAUSE
• Power off or loose electrical connection
• Thermostat out of calibration-set too high
• Defective contactor
• Blown fuses
• Transformer defective
• High pressure control open (if provided)
• Interconnecting low voltage wiring damaged
• Run or start capacitor defective (single phase only)
• Start relay defective (single phase only)
• Loose connection
• Compressor stuck, grounded or open motor winding
open internal overload.
• Low voltage condition
• Low voltage condition
• Improperly sized unit
• Improper airflow
• Incorrect refrigerant charge
• Air, non-condensibles or moisture in system
• Incorrect voltage
• Incorrect voltage
• Defective overload protector
• Refrigerant undercharge
• Low evaporator airflow
• Restriction in liquid line, expansion device or filter drier
• Incorrect capillary tubes
• Dirty condenser coil
• Refrigerant overcharge
• Condenser fan not running
• Air or non-condensibles in system
• Defective Compressor valves
• Incorrect capillary tubes
• Low evaporator airflow
• Operating below 65°F outdoors
• Moisture in system
• Excessive load
• Defective compressor
• Air or non-condensibles in system
• Air or non-condensibles in system
DANGER
• Check for correct voltage at compressor contactor in control
box
• Reset
• Check for 24 volts at contactor coil - replace if contacts are
open
• Replace fuses
• Check wiring-replace transformer
• Reset-also see high head pressure remedy-The high pressure
control opens at 450 PSIG
• Replace thermostat wiring
• Replace
• Replace
• Check for correct voltage at compressor -
check & 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 rating
plate volts when unit is operating.
• Add start kit components
• Recalculate load
• Check - should be approximately 400 CFM per ton.
• Charge per procedure attached to unit service panel.
• Recover refrigerant, evacuate & recharge, add filter drier
• At compressor terminals, voltage must be within 10% of rating
plate volts when unit is operating.
• At compressor terminals, voltage must be ± 10% of
nameplate marking when unit is operating.
• Replace - check for correct voltage
• Add refrigerant
• Increase speed of blower or reduce restriction - replace air
filter
• Remove or replace defective component
• Change coil assembly
• Clean coil
• Correct system charge
• Repair or replace
• Recover refrigerant, evacuate & recharge
• Replace compressor
• Replace coil assembly
• Increase speed of blower or reduce restriction - replace air
filter
• Add Low Ambient Kit
• Recover refrigerant - evacuate & recharge - add filter drier
• Recheck load calculation
• Replace
• Recover refrigerant, evacuate & recharge
• Recover refrigerant, evacuate & recharge
REMEDY
19