Addison PR Series - Refrigeration Circuit; Table 13.3: Refrigeration Circuit

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Problem Probable Cause Solution
Noisy Operation
Air noise Check ductwork Air Velocity too high
Chattering contactor
Check for adequate control voltage, check
for shorts or breaks, check thermostat,
check contactor points
Tubing rattle
Dampen by taping or clamping, bend tubing
away from contact where possible
High Suction Pressure
Excessive load on evaporator coil
Check for high entering wet bulb
temperature Check for excessive airflow
Broken compressor valves Scroll
compressors do not have valves
Scroll compressors should not be pumped
down below 5 PSI
Compressor is unloaded Recalibrate unloader pressure switch
Leaking check valve Check temperature across check valve
Expansion valve not secured to suction line
or TXV defective
Check the TXV, ensure bulb is insulated
High Discharge
Pressure
TXV setting Check TXV setting and calibrate superheat
Air inlet to condenser dirty or obstructed
Check for proper clearances and possible
air recirculation
Condenser fan, motor defective
Check condenser fan motor and
run capacitor
Condenser fan control has incorrect setting
Check calibration of low ambient head
pressure control
Suction Pressure
Too Low
Refrigerant undercharge Check pressures and subcooling
Blower running backwards
Interchange any two wires connected
to motor
Defective or improperly adjusted
expansion valve
Check superheat and adjust TXV
Dirty filter Check filter and evaporator coil
Too little airflow or low entering
air temperature
Check airflow and entering air wet
bulb conditions
Restriction in suction or liquid line Check refrigerant circuit for restriction
Head Pressure
Too Low
Insuicient refrigerant charge Check subcooling, check for leak
Defective or improperly adjusted
expansion valve
Check superheat and adjust TXV
Low suction pressure See above – suction pressure too low
Condenser fan control setting Check calibration of low ambient control
Compressor defective See above – high suction pressure
Liquid Line Too Hot
Refrigerant undercharged See above – high discharge pressure
High discharge pressure Restriction upstream at point of frosting
Suction Line Frosting
Insuicient evaporator airflow
Check airflow, check fan VFD,
closed dampers
Restriction in suction or liquid line Restriction upstream at point of frosting
Malfunctioning or defective expansion valve Check bulb of TXV
Table 13.3: Refrigeration Circuit
PR Series Installation, Operation, and Maintenance Manual