Rheem A18AZ Series - Troubleshooting Tips

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Table 18: Service Analyzer Chart (cont.)
ELECTRONIC EXPANSION VALVES (cont.)
SYMPTOM POSSIBLE CAUSE REMEDY
Compressor ood
back upon start-up
Refrigerant drainage from ooded evaporator
Install trap riser to the top of the evaporator coil.
Inoperable stator heat
Superheat is low
to normal with low
suction pressure
Unequal evaporator circuit loading
Recover refrigerant, replace lter-drier, evacuate
system, and recharge.
Check for blocked distributor tubes.
Low load or airow entering evaporator coil
Ensure blower is moving proper air CFM.
Remove/Correct any airow restriction.
Superheat and
suction pressure
uctuate (valve
is hunting)
Expansion valve is oversized. Install correct EXV
Section thermistor is affected by liquid refrigerant
or refrigerant oil owing through suction line
Relocate sensing bulb in another position around the
circumference of the suction line.
Unequal refrigerant ow through evaporator
circuit
Ensure sensing bulb is located properly.
Check for blocked distributor tubes.
Moisture freezing and partially blocking EXV
Recover refrigerant, change lter-drier, evacuate
system, and recharge.
Valve does not
regulate at all
Pressure transducer not connected or plugged
Connect pressure transducer in proper location, or
remove any blockage.
Suction line thermistor not connected, or
installed on heat effected zone.
Install suction line thermistor in correct horizontal
clean section of copper pipe.
Suction line thermistor failed (continuity to
control, wire damaged, resistance values
incorrect)
Replace suction line thermistor.
9.4 Troubleshooting Tips
Table 19: Cooling Mode Trouble Shooting Tips
SYSTEM
PROBLEM
INDICATORS
DISCHARGE
PRESSURE
SUCTION
PRESSURE
SUPERHEAT
Normal: 5°–15°F
[2.8° – 8.3°C]
SUBCOOLING
Normal: See
Charging Chart
Overcharge
High High Low High
Undercharge
Low Low High Low
Liquid Restriction
(Filter Drier)
Low Low High High
Low Indoor Airow
Low Low Low Low
Dirty Outdoor Coil
High High Low Low
Low Outdoor
Ambient Temperature
Low Low High High
Inefcient
Compressor
Low High High High
Bad Indoor Suction
Pressure Transducer or
Faulty Measurement
Low Low High High
Poorly Insulated
Indoor Vapor Line
Thermistor or Bad
Thermistor
High High Low Low