Carrier 48HC 04-28 Controls, Start-up, Operation And Troubleshooting

Also see for /50HC 04-28: Manual

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Carrier 48HC 04-28 Controls, Start-up, Operation And Troubleshooting Manual pdf 50 page image

50Cooling TroubleshootingUse the scrolling marquee display or a CCN device to view thecooling status display and the cooling diagnostic display (seeAppendix A) for information on the cooling operation. Checkthe current alarms and alarm history for any cooling alarmcodes and correct any causes. (See Table 14.) Verify anyunique control configurations per installed site requirements oraccessories.If alarms conditions are corrected and cleared, operation of thecompressors and fans may be verified by using the Service Testmode. (See Table 6.) See Table 16 for general cooling serviceanalysis.Table 16 — Cooling Service AnalysisPROBLEM CAUSE REMEDYCompressor and Fan Will Not Start. 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 ComfortLink scrolling marquee.Thermostat or occupancy schedule set point notcalling for Cooling.Check using ComfortLink scrolling marquee.Outdoor temperature too low. Check Compressor Lockout Temperature usingComfortLink scrolling marquee.Active alarm. Check active alarms using ComfortLink scrollingmarquee.Compressor Cycles (other than normallysatisfying thermostat).Insufficient line voltage. Determine cause and correct.Active alarm. Check active alarms using ComfortLink scrollingmarquee.Compressor Operates Continuously. Unit undersized for load. Decrease load or increase size of unit.Thermostat or occupancy schedule set point toolow.Reset thermostat or schedule set point.Dirty air filters. Replace filters.Low refrigerant charge. Check pressure, locate leak, repair, evacuate,and recharge.Condenser coil dirty or restricted. Clean coil or remove restriction.Excessive Condenser Pressures. Loose condenser thermistors. Tighten thermistors.Dirty condenser coil. Clean coil.Refrigerant overcharge. Recover excess refrigerant.Faulty TXV. 1. Check TXV bulb mounting and secure tightlyto suction 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 tightlyto suction 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,and recharge.Faulty TXV. 1. Check TXV bulb mounting and secure tightlyto suction 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.Compressor not running but ComfortLinkStatus show it is on.Condensate overflow switch, High pressure, orFreeze protection thermostat has tripped.Check Alarms. (T051 or T055), check switchesand conditions that can cause their trips.LEGENDTXV — Thermostatic Expansion Valve