Temperature Control - KitchenAid KBFC42FS Technical Education

TEMPERATURE CONTROL

The main electronic control board checks the
resistance of the thermistors, and compares it
to both the customer temperature settings and
the last thermistor reading taken. This infor-
mation is used to determine when to begin a
cooling operation, and if a change is necessary
in the damper setting, or the evaporator fan or
compressor speed.
When a warm refrigerator is first put into a cool-
ing mode, the air door partially opens, and the
compressor and evaporator fan motors start to
run at maximum rpm. The air door will gradually
move to its fully open position.
As the actual temperature in the refrigerator
nears the selected temperature setting, the
electronic control compares the temperatures
in both compartments. The compartment that
has the greatest need for cooling will control
the speed of the evaporator fan motor.
Freezer Temperature Control —
Temperature Increasing
When the freezer calls for cooling, the com-
pressor begins to run at minimum rpm, (see
the chart on page 3-3), and the evaporator fan
begins to run at 2000 rpm. The compressor and
evaporator speeds are continuously updated.
Speed changes are made based on:
• The difference between the actual tempera-
ture and the selected temperature settings.
• The rate of temperature change.
If the temperature increases 4°F above the
selected temperature setting, the evaporator
fan speed begins to gradually increase. The
evaporator fan motor reaches the maximum
speed of 3000 rpm at 5°F above the selected
temperature setting, and the compressor speed
begins to gradually increase. A maximum com-
pressor speed of 4500 rpm will be reached at
9°F above the selected temperature setting.
Freezer Temperature Control —
Temperature Decreasing
When the freezer temperature begins to de-
crease, the process will reverse. The com-
pressor speed decreases, followed by the
evaporator fan speed.
Refrigerator Temperature Control —
Temperature Increasing
When the refrigerator calls for cooling while the
freezer is satisfied, the air door begins to open,
and the evaporator fan starts to run at minimum
speed. If the temperature continues to rise, the
air door will continue to open. If the temperature
continues to rise after the air door is fully open,
the evaporator fan speed will gradually increase
to a maximum of 3000 rpm. If the temperature
continues to rise, the compressor starts to run,
or if it has already been running, begins to in-
crease in speed.
Refrigerator Temperature Control —
Temperature Decreasing
As the refrigerator temperature approaches
the selected setting, the control compares the
temperatures in both compartments to deter-
mine which compartment will control the fan
speed. If the freezer is further from the selected
temperature setting, it controls the fan speed,
and the air door begins to close, thus reducing
the airflow to the refrigerator.
If the freezer is satisfied, the air door remains
open, and the fan speed begins to decrease.
When the selected temperature setting is
reached, the air door closes.
3-2