39
9.3 Service Analyzer Charts
Table 18: Service Analyzer Chart
COMPRESSOR OVERHEATING – HIGH DISCHARGE TEMP
SYMPTOM POSSIBLE CAUSE REMEDY
High superheat
(greater than 15°F
[-8.3°C] at coil)
Low charge Check system charge.
Verify suction thermistor operation
(10k thermistor)
Replace thermistor.
Verify pressure transducer operation input and
output voltage
Replace thermistor and/or harness and/or control board.
Faulty metering device, inadequate suction
thermistor or pressure transducer operation.
Restricted cap tube, EXV
Foreign matter stopping ow
High internal load
Hot air (attic) entering return
Heat source on; miswired or faulty control
Restriction in liquid line
Drier plugged.
Line kinked.
Low head pressure
Low charge
Operating in low ambient temperatures
Vapor or liquid line subjected to high heat source
Hot attic
Hot water line
Low line voltage
Loose wire connections Check wiring.
Power company problem, transformer Report problem.
Undersized wire feeding unit Correct and complete diagnosis.
High head pressure
Overcharge Check system charge.
Dirty heat pump coil Clean coil.
Faulty or wrong size heat pump fan motor Replace fan motor.
Faulty fan blade or wrong rotation
Replace fan blade.
Replace with correct rotation motor.
Recirculation of air Correct installation.
Additional heat source
Check for dryer vent near unit.
Check for recirculation from other equipment.
Noncondensibles Recover refrigerant. Evacuate and recharge system.
Equipment not matched Correct mismatch.
Short cycling of
compressor
Cycling or faulty pressure control
Check pressure and address cause of high or
low pressure. Replace pressure control if faulty.
Loose wiring Check unit wiring.
Thermostat
Located in supply air stream
Differential setting too close
Customer misuse
EXV restricted or not functioning properly
Internal foreign matter
Pressure transducer failure
Suction thermistor failure
EXV control failure
EXV coil failure
Distributor tube restricted
Restricted with foreign matter
Kinked
Inside diameter reduced from previous compressor failure
Diagnostics
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