Carrier 50VT-A Troubleshooting, Start-Upchecklist, System Information, Loss of Charge Switch

50VT-- A

Puron (R-410A) Refrigerant Charging

Refer to unit information plate and charging chart. Some R-410A refrigerant cylinders contain a dip tube to allow liquid refrigerant to flow from cylinder in upright position. For cylinders equipped with a dip tube, charge Puron units with cylinder in upright position and a commercial metering device in manifold hose. Charge refrigerant into suction-line.

Step 13 — 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 psig. Never open system without breaking vacuum with dry nitrogen.

Check Defrost Thermostat

The defrost thermostat is usually located on the lowest liquid leaving circuit of the left condenser coil (see Fig. 22). The thermostat closes at 32_F (0_C) and opens at 65_F (18_C).

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 32_  3_F (0

1.7_C) and open at 65_  5_F (18  2.8_C).

NOTE: The defrost thermostat must be located on the liquid side of the outdoor coil on the bottom circuit and as close to the coil as possible.

FEEDER TUBE

STUB TUBE

DEFROST

THERMOSTAT

C99029

Fig. 22 - Defrost Thermostat

TROUBLESHOOTING

Refer to the Cooling and Heating Troubleshooting Chart (Table 10) for troubleshooting information.

START-UP CHECKLIST

Use the Start-Up Checklist.

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