Fujitsu FO20R Series Installation Instructions Manual page 68

Variable speed r-410a heat pump outdoor units
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9.0 DIAGNOSTICS & TROUBLESHOOTING
9.12 Service Analyzer Charts (cont.)
Moisture
High head pressure
Unusual head and
suction pressure
readings
Foreign matter –
Copper oxide
Welding scale
Excess soft solder
Compressor failures
Low suction pressure
Cold, noisy
compressor –
Slugging
Noisy compressor
Cold, sweating
compressor
Low load
Short cycling of
compressor
On start-up
EXV hunting when
running
68
Poor evacuation on installation or during service
Noncondensibles air
Wrong refrigerant or mixed refrigerants
Copper tubing cuttings
Dirty copper piping or nitrogen not used when
brazing
Nitrogen not used during brazing
Wrong solder material
Vapor line tubing too large
Low charge
Refrigerant leaks
Dilution of oil with refrigerant
Migration
Flooding
Thermostat setting
Cycling or faulty high or low pressure control
Loose wiring
Thermostat
Incorrect piping
Faulty EXV components
In each case, the cure is the same. Recover refrigerant,
flush system. Add filter driver, evacuate, and recharge.
Reduce tubing size to improve oil return.
Check system charge.
Repair and recharge.
Observe piping guidelines.
Check stater heat and compressor thermistor.
Check system charge.
Dirty coil
Wrong duct size
Restricted duct
Advise customer.
Check pressure and address cause of any abnormal
pressure. Replace control if faulty.
Check all control wires.
In supply air stream, out of calibration
Customer misuse
Review pipe size guidelines.
Check EXV, suction pressure transducer, and suction
thermistor for operation.

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