225TROUBLESHOOTING GUIDETable 174 shows potential unit issues and possible solutions. Thistable is meant only as a guide, and is not exhaustive in issues orsolutions.Table 174 — TroubleshootingLEGENDSYMPTOM POSSIBLE CAUSE POSSIBLE REMEDYUnit Does Not Run Check for power to unit • Check overcurrent protection device.• Check non-fused disconnect (if equipped).• Restore power to unit.• Check Active Capacity Override, CAPA_override.Wrong or incorrect unitconfigurationCheck unit configuration.Active alarm Check Alarm status. See the Alarms and Alerts section and follow troubleshooting instructions.Active operating mode Check for Operating Modes. See the Operating Modes section and follow troubleshooting instruc-tions.High pressure switch (HPS) open • Recheck high pressure switch.• Check HPS wiring in compressor VFD.VFD Enable • Check VFD enable output from SIOB J6-DO04 for 24VAC.• Check wiring in compressor VFD at terminals 13 and 27.Unit Operates Too Long orContinuouslyLow refrigerant charge Check for leak and add refrigerant.Air in chilled water loop Purge water loop.Non-condensables inrefrigerant circuitRemove refrigerant and recharge.Inoperative EXV • Check EXV, clean or replace.• Check EXV cable, replace if necessary.• Check EXV board for output signal.Load too high Unit may be undersized for application.Circuit Does Not Run Active alarm Check Alarm status. See the Alarms and Alerts section and follow troubleshooting instructions.Check Active Capacity Override, CAPA_override.Active operating mode Check for Operating Modes. See the Operating Modes section and follow troubleshooting instruc-tions.Check Active Capacity Override, CAPA_override.Circuit Does Not Load Active alarm Check Alarm status. See the Alarms and Alerts section and follow troubleshooting instructions.Active operating mode Check for Operating Modes. See the Operating Modes section and follow troubleshooting instruc-tions.Low saturated suctiontemperature See Capacity Control Overrides #23 and #24.High circuit suction superheat The circuit capacity is not allowed to increase if circuit superheat is greater than 36°F (20°C).• Check for faulty suction transducer or wiring.• Check for restriction in liquid line (filter drier, service valve, etc.).• Check EXV operation.• Check for proper refrigerant charge.Low suction superheat The circuit capacity is not allowed to increase if circuit superheat is less than 18°F (10°C).• Check for faulty suction transducer or wiring.• Check for restriction in liquid line (filter drier, service valve, etc.).• Check EXV operation.• Check for proper refrigerant charge.Low discharge superheat The circuit is not allowed to increase if discharge superheat is below 16.2°F (–8.8°C).• Check for faulty suction transducer or wiring.• Check for restriction in liquid line (filter drier, service valve, etc.).• Check EXV operation.• Check for proper refrigerant charge.Compressor or Fans Do NotRunActive alarm Check Alarm status. See the Alarms and Alerts section and follow troubleshooting instructions.Active operating mode Check for Operating Modes. See the Operating Modes section and follow troubleshooting instructions.VFD fuses blown Check compressor and fan VFD fuses and replace if necessaryChilled Water Pump is ON, butthe Machine is OFFEvaporator freeze protection Chilled water loop temperature too low. Check evaporator heater.EXV — Electronic Expansion ValveHPS — High Pressure SwitchVFD — Variable Frequency Drive