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Troubleshooting – Refrigeration Circuit
Symptom
Possible Cause
Excessive load on evaporator coil.
Compressor is unloaded.
(digital scroll)
Expansion valve sensing bulb not
High suction
secured to suction line.
pressure
Thermostatic expansion valve.
Overfeeding.
Room load too large.
Overcharged.
Thermal expansion valve setting.
Air inlet to condenser dirty or
obstructed.
Condenser fan motor defective.
High
Too much refrigerant.
discharge
pressure
Non-condensable in system.
Dirty condenser coil.
Condenser fan not running or running
backwards.
High load conditions.
Refrigerant undercharge/loss of
refrigerant charge.
Blower running backward.
Low entering air temperature.
(Low load conditions).
Refrigerant leak.
Low suction
Evaporator dirty or iced-up, or airflow
pressure
restricted.
Plugged liquid line filter-drier.
Improper hot gas bypass setting.
Expansion valve defective, superheat
too high or valve too small.
Moisture in system, check sight glass.
Always have a completed Pre-Start-Up Checklist and Start-Up Checklist prior to requesting parts or service information.
Corrective Action
Check for high entering wet bulb temperature, check for
excessive air flow.
Check digital scroll controller signal and solenoid valve.
Check the thermal expansion valve, ensure bulb is
insulated. Check superheat. If superheat is high, then
valve is choking refrigerant flow.
• Check bulb for contact.
• Adjust valve for superheat ~10°F.
• Replace valve power head or valve.
Check bulb location and clamping. Adjust superheat.
Replace expansion valve power head.
Reduce the load or add more equipment.
Check pressures and subcooling.
Check thermal expansion setting and calibrate
superheat / subcooling.
Check for proper clearances and possible air
recirculating. Clean coil.
Check condenser fan motor.
Check subcooling. Remove excess refrigerant.
Remove non-condensable from system.
Clean condenser coil.
Check electrical circuit and fuse. Check fan cycling
controls.
Add more equipment or reduce load.
Check pressures and subcooling.
Confirm blower rotation. If reversed, interchange any two
wires from 3-phase disconnect.
Check entering air wet bulb conditions.
Check system for leaks. Repair leaks and add refrigerant.
Clean the coil. Check fan operation. Check airflow.
Replace filter-drier, check psi across filter.
Check setting and correct as required.
Adjust valve for proper superheat or replace the
expansion valve if too small or defective.
Reclaim refrigerant, check for leaks, recharge.
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- Unit Nomenclature
- General Data
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