Rheem A180CL25E Installation Instructions Manual page 27

Combination heating and cooling rooftop units 15, 20 & 25 ton (-)kkb and 15 & 20 ton (-)kmb units
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!
WARNING
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 pressure-
low vapor pressures
High head pressure-high or
normal vapor pressure -
Cooling mode
Low head pressure-high vapor
pressures
Low vapor pressure -
cool compressor -
iced evaporator coil
High vapor pressure
Fluctuating head & vapor
pressures
Gurgle or pulsing noise at
expansion device or liquid line
COOLING TROUBLE SHOOTING CHART
POSSIBLE CAUSE
• Power off or loose electrical connection
• Thermostat out of calibration-set too high
• Failed contactor
• Blown fuses
• Transformer defective
• High pressure control open (if provided)
• Interconnecting low voltage wiring damaged
• 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
• Flow check piston size too small
• Incorrect capillary tubes
• TXV does not open
• 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
• TXV hunting
• Air or non-condensibles in system
• Air or non-condensibles in system
FIGURE 24
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
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 to correct size piston
Change coil assembly
Replace TXV
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
Check TXV bulb clamp - check air distribution on coil - replace
TXV
Recover refrigerant, evacuate & recharge
Recover refrigerant, evacuate & recharge
REMEDY
27

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