System Diagnosis
Refrigerant Overcharge Symptoms
•Above normal freezer temperature.
•Compressor running continuously.
•Freezing in refrigerator due to Chef’s Pantry™
.•High suction and head pressure.
•High wattage.
•Warm evaporator inlet and outlet temperature.
•Below ambient suction tube temperature. Check for separated heat exchanger when suction temperature is colder than ambient.
•Refrigerant will flood out causing suction line to frost or sweat, if defrost system fails and cooling coil is not defrosted. Correct problem instead of purging refrigerant.
•Freezer colder than necessary (normal package temperature is 0° to 2°F).
•Evaporator fan motor not running.
Refrigerant Shortage Symptoms
•Rise in refrigerator and freezer temperatures. Warm beverages will be first indication of possible refrigerant shortage. Frozen meats and vegetables will not thaw immediately. Some freezing may occur in refrigerator section due to additional run time because of Chef’s Pantry™ . Capillary line will not have full column of liquid with refrigerant shortage. A noticeable hissing sound in evaporator will be heard. Hissing should not be mistaken for regular refrigerant boiling sounds.
•Long or continuous run time.
•Traces of oil caused by leak or cracked refrigerant line.
•Lower than normal wattage.
•Compressor will feel hot due to heat generated by motor windings from continuous running. Compressor will not be as hot as it would be with full charge and long run times caused by reasons such as dirty condenser.
•Condenser will feel room temperature.
•Capillary tube will feel warmer than normal.
•If high side leak, both gauges will show lower than normal readings. As charge becomes less, readings will lower. Suction pressure gauge will probably indicate a vacuum.
•If low side leak, suction pressure gauge will show lower than normal readings, probably in a vacuum. Head pressure gauge will show higher than normal. Readings will probably rise because of air drawn in through leak is compressed by compressor and accumulates in high side (condenser) of system.
•Partial frosting of evaporator.
Restriction Symptoms
•Refrigeration cooling occurs on low pressure side of partial restriction.
•Total restriction will stop circulation of refrigerant and no cooling will occur.
•Touch refrigeration lines. Most common place for restriction is at drier filter or capillary tube inlet or outlet.
•If partial restriction there will be temperature difference at restriction point. Evaporator side will be cooler. In most cases, frost and/or condensation will be present. Longer time is required for system to equalize.
•Kinked line will cause restriction. Visually check entire system for kinks.
•Slight restriction will give same indications as refrigerant shortage with lower than normal back pressure, head pressure, wattage, and warmer temperatures.
•If total restriction is on discharge side of compressor, higher than normal head pressures and wattages will occur. This is only true while low side is being pumped out and if restriction was between compressor and first half of condenser.
Diagnose restriction by completing the following:
1.Discharge system.
2.Replace
3.Evacuate and recharge system with specified refrigerant charge.
If refrigerator performs normally, the following conditions may exist:
•refrigerant loss
•partially restricted drier
•moisture in system
If refrigerator performs as previously described, capillary line or condenser may be restricted. Locate and correct restriction point.
Restriction reduces refrigerant flow rate and heat removal rate. Total restriction may be caused by moisture, poorly soldered joint, or solid contaminants in system. Moisture freezes at evaporator inlet end of capillary tube. Solid contaminants collect in drier. Wattage drops because compressor is not circulating normal amount of refrigerant.
If restriction is on low side suction, pressure will be in a vacuum and head pressure will be near normal. If restriction is on high side, suction pressure will be in a vacuum and head pressure will be higher than normal during pump out period. In both cases, it will take longer than 10 minutes for head pressure to equalize with low side after compressor stops.
November 1996 | 11 | RS1200001 |