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Fujitsu FO20R Series Installation Instructions Manual page 65

Variable speed r-410a heat pump outdoor units
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9.11 General Troubleshooting Guide
WARNING:
Failure to shut off power can cause electrical shock resulting in personal injury or death.
SYMPTOM
Unit will not run
• Power off or loose electrical connection
• Thermostat set too high or low.
• Unit in active compressor protection
lockout mode
• Blown fuses/tripped breaker
• Transformer defective
• High-pressure control lock-out
• Low-pressure control lock-out
• Miswiring of communications (communication
light on continuously)
• Defective control board
Outdoor fan runs,
• Loose connection
compressor doesn't
• Communication cable disconnected or failed
• Compressor stuck, grounded or open motor
winding, open internal overload.
• Low-voltage condition
• Improperly sized unit
• Incorrect refrigerant charge
• Air, noncondensibles, or moisture in system
• Restricted Refrigerant Circuit
Compressor short
• Incorrect voltage
• Improperly sized unit
cycles
• Refrigerant undercharge or overcharge
• (LPC or HPC Cycling)
Registers sweat
High head, low vapor
• Restriction in liquid line, expansion device, or
pressures
• Stuck EXV
High head, high
• Dirty outdoor coil
or normal vapor
• Refrigerant overcharge
pressure – Cooling
• Outdoor fan not running
mode
• Air or noncondensibles in system
Low head, high vapor
• EXV in bypass mode
pressures
• Reversing Valve leaking by
• Bad compressor
Low vapor, cool
compressor, iced
• Operating below 55°F outdoors
indoor coil
• Moisture in system
• Low ambient cooling not operating (coil or
ambient thermistor failure)
High vapor pressure
• Excessive load
• Defective compressor
Fluctuating head and
• EXV hunting
vapor pressures
• Air or noncondensibles in system
Gurgle or pulsing
• Air or noncondensibles in system
noise at expansion
• Undercharge long line application
device or liquid line
9.0 DIAGNOSTICS & TROUBLESHOOTING
Disconnect all power to unit before servicing. Contactor may break only one side.
POSSIBLE CAUSE
REMEDY
• Check for correct voltage at line voltage connections in
condensing unit.
• Reset – Power cycle high and low voltage to outdoor
unit.
• Check control board diagnostic codes.
• Replace fuses/reset breaker.
• Check wiring. Replace transformer.
• Reset by cycling power to unit. Also see high head
pressure and low suction pressure remedies.
• Check for refrigerant leaks.
• Check communication wiring.
and tighten all connections.
• Check control board diagnostic codes.
• Replace
• Recalculate load.
ton.
• Charge per procedure attached to unit service panel.
• Recover refrigerant. Evacuate and recharge.
• Locate restriction and clear
• At inverter input terminals, voltage must be between
187-252 VAC when unit is operating.
• Adjust charge per charging chart.
• Increase speed of blower or reduce restriction.
• Remove or replace defective component.
• Verify EXV operation.
• Clean coil.
• Correct system charge.
• Repair or replace.
• Recover refrigerant. Evacuate and recharge.
• Verify thermostat connections at EXV control
• Verify thermistor and pressure transducer connection
and operation
• Replace reversing valve
• Replace compressor.
• Increase speed of blower or reduce restriction.
• Recover refrigerant. Evacuate and recharge. Replace
• Recheck load calculation.
• Replace compressor.
• Check thermistor to vapor line connection. Check air
distribution on coil.
• Check suction thermistor and pressure transducer
operation
• Recover refrigerant. Evacuate and recharge.
with nitrogen to remove any debris then reinstall
• Recover refrigerant. Evacuate and recharge.
• Adjust charge per charging chart.
65

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