Carrier 50CR System Information, LOSS-OF-CHARGE Switch, Check Defrost Thermostat, Troubleshooting

Page 28

Step 14—System Information

LOSS-OF-CHARGE SWITCH

The loss of charge switch is a protective device wired into control circuit (low voltage). It shuts off the compressor if abnormally low pressures are present in the refrigeration circuit.

NOTE: Because these switches are attached to refrigeration system under pressure, it is not advisable to remove this device for troubleshooting unless you are reasonably certain that a problem exists. If switch must be removed, remove and recover all system charge so that pressure gauges read 0 psi. Never open system without breaking vacuum with dry nitrogen.

CHECK DEFROST THERMOSTAT

There is a liquid header with a brass distributor and feeder tube going into outdoor coil. At the end of one of the feeder tubes, there is a 3/8-in. OD stub tube approximately 3 in. long (See Fig. 27). The defrost thermostat should be located on stub tube.

NOTE: There is only one stub tube used with liquid header, and on most units it is the bottom circuit.

The defrost thermostat signals heat pump that conditions are right for defrost or that conditions have changed to terminate defrost. It is a thermally-actuated switch clamped to outdoor coil to sense its temperature. Normal temperature range is closed at 30° ± 3°F and open at 80° ± 5°F.

TROUBLESHOOTING

Refer to the Cooling and Heating Troubleshooting Chart (Table 7) for troubleshooting information.

START-UP CHECKLIST

Use the Start-Up Checklist at the back of this manual.

Unit Top

Defrost

Sensor

Detail A

See

Detail A

A06068

Fig. 27 - Defrost Sensor Location

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Contents Installation Instructions Table of ContentsSafety Considerations Electrical Shock HazardEquipment Damage Hazard IntroductionRoof Curb for Small Cabinet Roof Curb for Large Cabinet Unit Leveling Tolerances 50CR024-036 Unit Dimensions 50CR042-060 Unit Dimensions Rig and Place Unit InspectionUnit Falling Hazard Property Damage HazardRigging Bracket Under Unit Rain Lip Electrical Operation Hazard Select and Install DuctworkProvide for Condensate Disposal Typical Installation Physical Data Unit 50CRRouting Power Leads Into Unit Connecting Ground Lead to Ground ScrewRouting Control Power Wires HIGH-VOLTAGE ConnectionsElectrical Data-50CR Electrical Data Legend Wiring Schematics-50CR Single Phase Wiring Schematics-50CR Three Phase Accessory Installation Line Power ConnectionsSTART-UP PRE-START-UP FIRE, EXPLOSION, Electrical Shock HazardUnit Start-Up Status Code 45, Control Board Test Fault Status Code 37, Heater Output Sensed on When not EnergizedStatus Code 44, Motor Communication Fault Verify Motor Winding SectionStatus Code 36, Heater Output not Sensed When Energized Status Code 41, Blower Motor FaultStatus Code 16, System Communication Fault Status Code 25, Invalid Motor / Model SelectionSequence of Operation Start-Up AdjustmentsCheck for Refrigerant Leaks Typical Heat Pump Operation, Cooling Mode Defrost Control Electric Heat Pressure Drop Table Small Cabinet Personal Injury and Unit Damage Hazard MaintenanceUnit Operation Hazard Air Filter Indoor Blower and MotorOutdoor Coil, Indoor Coil, and Condensate Drain Pan Outdoor FanIndoor Airflow Pressure SwitchesMetering Devices-TXV & Accurater Piston EXPLOSION, FIRE, Electrical Shock Hazard High-Pressure SwitchPersonal INJURY, Unit Operation Hazard LOSS-OF-CHARGE Switch TroubleshootingSTART-UP Checklist System InformationObserve all warnings, cautions, and bold text Troubleshooting Chart Troubleshooting Chart Cont’d Head pressure too lowSTART-UP Checklist
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