SERVICING THE REFRIGERATOR SECTION
The refrigerant cycle is a continuous cycle, which occurs whenever the compressor is operating. Liquid refrigerant is evaporated in the evaporator by the heat that enters the cabinet through the insulated walls and by product load and door openings. The refrigerant vapor passes from the evaporator through the suction line to the compressor dome, which is at suction pressure. From the top interior of the dome, the vapor passes down through a tube into the pump cylinder. The pressure and temperature of the vapor are raised in the cylinder by compression. The vapor is then forced through the discharge valve into the discharge line and the condenser. Air passing over the condenser surface removes heat from the high-pressure vapor, which then condenses to a liquid. The liquid refrigerant flows from the condenser to the evaporator through the small-diameter liquid line (capillary tube). Before it enters the evaporator, it is subcooled in the heat ex- changer by the low-temperature suction vapor in the suction line.
Sealed Compressor and Motor
All models are equipped with a compressor with internal spring suspension. Some compressors have a plug- in magnetic starting relay, with a separate motor overload protector. Others have a built-in metallic motor overload protector. When ordering a replacement compressor, you should always give the refrigerator model number and serial number and the compressor part number. Every manufacturer has a listing avail- able to servicepersons.
Condenser
Side-by-side and top-freezer models with a vertical natural-draft, wire-tube-type condenser have a water- evaporating coil connected in series with the condenser. The high-temperature, high-pressure, compressed refrigerant vapor passes first through the water-evaporating coil. There, part of the latent heat of evapora- tion and sensible heat of compression are released. The refrigerant then flows back through the oil cooling coil in the compressor shell. There, additional heat is picked up from the oil. The refrigerant then flows back to the main condenser, where sufficient heat is released to the atmosphere. This results in the condensation of refrigerant from a high-pressure vapor to high-pressure liquid.
Filter Drier
A filter drier is located in the liquid line at the outlet of the condenser. Its purpose is to filter or trap minute particles of foreign materials and absorb any moisture in the system. Fine mesh screens filter out foreign par- ticles. The desiccant absorbs the moisture.
Capillary Tube
The capillary tube is a small-diameter liquid line connecting the condenser to the evaporator. Its resistance, or pressure drop, due to the length of the tube and its small diameter, meters the refrigerant flow into the evaporator.
The capillary tube allows the high-side pressure to unload, or balance out, with the low-side pressure dur- ing the off-cycle. This permits the compressor to start under a no-load condition.
The design of the refrigerating system for capillary feed must be carefully engineered. The capillary feed must be matched to the compressor for the conditions under which the system is most likely to operate. Both the high side (condenser) and the low side (evaporator) must be specifically designed for use with a capillary tube.
Heat Exchanger
The heat exchanger is formed by soldering a portion of the capillary tube to the suction line. The purpose of the heat exchanger is to increase the overall capacity and efficiency of the system. It does this by using the cold suction gas leaving the evaporator to cool the warm liquid refrigerant passing through the capillary tube to the evaporator. If the hot liquid refrigerant from the condenser were permitted to flow uncooled into the evaporator, part of the refrigerating effect of the refrigerant in the evaporator would have to be used to cool the incoming hot liquid down to evaporator temperature.
Freezer Compartment and Provision Compartment Assembly
Liquid refrigerant flows through the capillary and enters the freezer evaporator. Expansion and evapora- tion starts at this point.