43
10.7
Service Analyzer Chart (cont.)
Diagnostics
COMPRESSOR OVERHEATING
SYMPTOM POSSIBLE CAUSE CHECK/REMEDY
High superheat
(greater than
15
o
F [8.3
o
C] at
coil)
Low charge Check system charge
Verify suction thermistor operation Replace thermistor
Verify pressure transducer operation input and
output voltage
Replace transducer and/or harness and/or control board
Faulty metering device (EXV or TXV) Foreign matter stopping ow. Clean EXV or TXV inside
with nitrogen
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
Suction or liquid line subjected to high heat source Hot attic / insulate liquid line and suction line
Hot water line / isolate from suction or liquid line
Low line voltage
Loose wire connection Check wiring
Power company problem Report problem
Undersized wire feeding unit Correct and complete diagnosis
High line voltage Power company problem Report problem
High head
pressure
Overcharge Check system charge
Dirty outdoor coil Clean coil
Faulty or wrong size outdoor fan motor Replace fan motor. Check capacitor
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 or
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 or TXV restricted Internal foreign matter. Clean with nitrogen
Pressure transducer failure
Suction thermistor or sensing bulb failure
EXV control failure
EXV coil failure
Distributor tube/tubes restricted
TXV equalizer tube plugged
10.0 DIAGNOSTICS AND TROUBLESHOOTING
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