Carrier 48FC Series Controls, Start-up, Operation And Troubleshooting

Also see for 48FC 04: Installation instructions

Carrier 48FC Series Controls, Start-up, Operation And Troubleshooting Manual pdf 35 page image

35Cooling TroubleshootingUse the SystemVut Display or a CCN device to view the coolingstatus display and the cooling diagnostic display (see Appendices)for information on the cooling operation. Check the current alarmsand alarm history for any cooling alarm codes and correct anycauses. (See Table 12.) Verify any unique control configurationsper installed site requirements or accessories.If alarms conditions are corrected and cleared, operation of thecompressors and fans may be verified by using the Service Testmode. (See Table 4.) See Table 14 for general cooling serviceanalysis.Table 14 – Cooling Service AnalysisPROBLEM CAUSE REMEDYCompressor and Fan Will NotStart.Power failure. Call power company.Fuse blown or circuit breaker tripped. Replace fuse or reset circuit breaker.Disconnect off. Power disconnect.Compressor time guard to prevent short cycling. Check using SystemVu Display.Thermostat or occupancy schedule set point notcalling for Cooling.Check using SystemVu Display.Outdoor temperature too low. Check Compressor Lockout Temperature usingSystemVu Display.Active alarm. Check active alarms using SystemVu ScrollingMarquee.Compressor Cycles (other thannormally satisfying thermostat).Insufficient line voltage. Determine cause and correct.Active alarm. Check active alarms using SystemVu ScrollingMarquee.Compressor OperatesContinuously.Unit undersized for load. Decrease load or increase size of unit.Thermostat or occupancy schedule set point too low. Reset thermostat or schedule set point.Dirty air filters. Replace filters.Low refrigerant charge. Check pressure, locate leak, repair, evacuate, andrecharge.Condenser coil dirty or restricted. Clean coil or remove restriction.Excessive Condenser Pressures. Dirty condenser coil. Clean coil.Refrigerant overcharge. Recover excess refrigerant.Faulty TXV. 1. Check TXV bulb mounting and secure tightly tosuction line and insulate.2. Replace TXV (and filter drier) if stuck open orclosed.Condenser air restricted or air short cycling. Determine cause and correct.Restriction in liquid tube. Remove restriction.Condenser Fans Not Operating. No Power to contactors. Fuse blown or plug at motor loose.Excessive Suction Pressure. High heat load. Check for sources and eliminateFaulty TXV. 1. Check TXV bulb mounting and secure tightly tosuction line and insulate.2. Replace TXV (and filter drier) if stuck open orclosed.Refrigerant overcharged. Recover excess refrigerant.Suction Pressure Too Low. Dirty air filters. Replace air filters.Low refrigerant charge. Check pressure, locate leak, repair, evacuate, andrecharge.Faulty TXV. 1. Check TXV bulb mounting and secure tightly tosuction line and insulate.2. Replace TXV (and filter drier) if stuck open orclosed.Insufficient evaporator airflow. Check belt tension. Check for other restrictions.Temperature too low in conditioned area (lowreturn-air temperature). Reset thermostat or occupancy schedule.LEGENDTXV --- Thermostatic Expansion Valve