Frigidaire LGUB2642LF2, Руководство по обслуживанию

Страница: 179 / 187

8-1
Principles Of Automatic Defrost
Operation
Automatic defrost refrigerators operate on the principle
that moisture or frost transfers or migrates to the coldest
surfaces (evaporator) in the freezer compartment. For
example, a small amount of water spilled in the freezer
compartment will freeze immediately. However, this ice
in time will evaporate and transfer to the colder surfaces
of the freezer such as the evaporator coil.
Air Circulation Patterns
Automatic defrost models have a single evaporator in the
freezer compartment, and have forced air cooling in the
freezer and refrigerator compartments. The “fin and
tube” aluminum type evaporator is located behind the
back wall of the freezer compartment. A circulating fan
(suction type) pulls air from the freezer compartment
through the grill in the bottom of the freezer and from the
refrigerator compartment through a grill located in each
bottom rear corner of the food compartment cabinet
interior. The air is than drawn up through the fin and
tubes of the evaporator surface. The cold air is forced
into a fan cover and discharged into the top of the
freezer. (See Figure 8-1).
NOTE: Non-dispenser models with the ice maker in
the freezer compartment have an air duct added to the
evaporator cover. This air duct directs air across the ice
maker assembly. The air flows in the same general
pattern as shown in Figure 8-1.
The air circulating fan operates any time the thermistors
sense the temperature of the food compartment or the
freezer compartment are above the upper control limit
and send the information to the lower control board. If
the food compartment is calling for cooling the automatic
damper in the back air channel behind the crisper drawer
of the food compartment will open and allow cold air to
enter the food compartment. The air is then carried up
the air channel to the top and discharges into the top of
the food compartment. If the food compartment calls
for cooling but the fan is not running, the fan will start as
soon as the damper is open, and will continue to run as
long as the food compartment and/or the freezer
compartment calls for cooling. The freezer thermistor
will stop the compressor if the freezer compartment goes
below the lower control limit and restart the compressor
on low speed as soon as the temperature in the freezer
goes back into the normal operating range.
The air circulating fan is a 12 V DC fan motor that
operates any time the food compartment or the freezer
compartment calls for cooling. During the defrost period,
the compressor and circulating fan do not operate. The
power board, located under the freezer behind the grill,
opens the electrical circuit to the fan motor and
compressor for the defrost cycle. The lower control
board also closes the damper door that is controlled by
a 12 V DC stepper motor, and keeps the damper door
closed during the complete defrost cycle.
If the product is equipped with a perfect temperature
drawer, it will pull air from the freezer through a small
opening in the right side of the bottom of the liner, just
in front of the air return opening. A fan controlled by
the electronic drawer control will pull the air up from the
freezer through the drawer and the air will return to the
freezer by way of the right air return opening in the liner.
Figure 8-1. Cabinet Air Flow
Air Circulation