Domestic Refrigerators
Most domestic refrigerators are of two types—either
a single door fresh food refrigerator or a two-door refrigerator-freezer combination, with
the freezer compartment on the top portion of the cabinet, or a vertically split cabinet
(side-by-side), with the freezer compartment on the left side of the cabinet. They are
completely self-contained units and are easy to install. Most refrigerators use R-22
refrigerant, normally maintaining temperatures of 0°F in the freezer compartment and
about 35°F to 45°F in the refrigerator compartment. The technician must be able to
perform various duties in the maintenance and repair of domestic refrigerators, water
coolers, and ice machines. This section provides information to aid you in handling some
of the more common types of troubles. But let us remind you that the information given
here is intended as a general guide and should, therefore, be used with the manufacturer's
detailed instructions.
Single Door Fresh Food Refrigerator
A single door fresh food refrigerator
(fig. 6-38) consists of an evaporator placed either across the top or in one of the upper
corners of the cabinet. The condenser is on the back of the cabinet or in the bottom of
the cabinet below the hermetic compressor. During operation, the cold air from the
evaporator flows by natural circulation through the refrigerated space. The shelves inside
the cabinet are constructed so air can circulate freely past the ends and sides,
eliminating the need for a fan. This refrigerator has a manual defrost, which requires
that the refrigerator be turned off periodically (usually overnight) to enable the buildup
of frost on the evaporator to melt. Both the outside and inside finish is usually baked-on
enamel. Porcelain enamel is found on steel cabinet liners. The interior of the unit
contains the shelves, lights, thermostats, and temperature controls.
Two-Door Refrigerator-Freezer
Combination
The two-door refrigerator-freezer
combination is the most popular type of refrigerator. It is similar to the fresh food
refrigerators in construction and the location of components except it sometimes has an
evaporator for both the freezer compartment and the refrigerator compartment. Also, if it
is a frost-free unit, the evaporators are on the outside of the cabinet.
Because of the two separate
compartments (refrigerator-freezer) and the larger capacity, these types of refrigerators
use forced air (fans) to circulate the air through the inside of both compartments. The
two-door refrigerator also has one of the following three types of evaporator defrost
systems: manual defrost, automatic defrost, or frost-free.
There are two types of automatic
defrosting: the hot gas system or the electric heater system. The hot gas system, through
the use of solenoid valves, uses the heat in the vapor from the compressor discharge line
and the condenser to defrost the evaporator. The other system uses electric heaters to
melt the ice on the evaporator surface.
A frost-free refrigerator-freezer
(fig. 6-39) has the evaporator located outside the refrigerated compartment. On the
running part of the cycle, air is drawn over the evaporator and is forced into the freezer
and refrigerator compartments by a fan. On the off part of the cycle, the evaporators
automatically defrost.
Refrigerator-freezer cabinets are made
of pressed steel with a vinyl or plastic lining on the interior wall surfaces and a
lacquer exterior finish. Most domestic refrigerators have urethane foam or fiber glass
insulation in the cabinet walls. The side-by-side refrigerator-freezer arrangement has a
number of features not found in other refrigerators. In addition to the automatic icemaker
in the freezer compartment, it has an option for a cold water dispenser, a cube or crushed
ice dispenser, and a liquid dispenser built into the door. |
