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The refrigerator temperature determines the
opening of the air door. When the refrigerator
requires cooling, if the evaporator fan motor is
already running for the freezer, the air door
partially opens, and then adjusts, if necessary.
While the refrigerator is cooling, the door will
be adjusting continuously to maintain or re-
cover refrigerator temperature.
ADAPTIVE DEFROST
The adaptive defrost control allows the unit to
enter a defrost mode only when it is needed.
When powered up for the first time, the control
initiates a defrost cycle after 8 hours of com-
pressor run time. By monitoring the duration of
defrost heating time and compressor run time,
the control will continuously adapt the time
between defrosts to optimize efficiency. Time
between defrost periods will vary between 8
and 100+ hours.
Defrost will occur immediately when the com-
pressor has run at 4000 rpm or greater for 1
hour, and 8 hours have elapsed since the last
defrost.
PULSED DEFROST
For the first 7 minutes of defrost, the heater is
on continuously. It will then cycle off for 1
minute, and back on for 2 minutes. The heater
will continue to cycle at this ratio until the
bimetal opens, or until 33 minutes has elapsed.
At this point, heat is discontinued, and a
4-minute “drip time” begins. This allows the
water to drain before the unit returns to a
cooling mode. Maximum defrost time, (pulsed
heat on/off time + drip time) is 37 minutes.
When entering a defrost cycle, if the bimetal is
open, the time to defrost is reset to 8 hours, and
the control will time through the entire 37 minute
defrost period. During diagnostics this will al-
low a technician time to look for heater opera-
tion, and if necessary, bypass the bimetal.
POWER INTERRUPTION
After a power interruption, the following events
will occur:
• The unit returns to the same operating mode
and settings in use prior to the power inter-
ruption. If the unit was off, it remains off.
• Initially, the compressor, evaporator fan, and
condenser fan motors will be off.
• The air door will close, and then adjust to the
proper opening. The evaporator fan starts
when the air door opens.
• The adaptive defrost control resets the com-
pressor run time counter to 0, and if the
freezer is above 20°F, the time to defrost is
set to 8 hours.
• If the freezer temperature is below 12°F, the
compressor starts after a delay of 7 minutes.
If the freezer temperature is above 12°F, the
compressor starts immediately.
FAILURE DEFAULTS
In the event of a thermistor, or keypad failure,
the control uses one of the following default
modes, which will continue until the failure is
corrected.
Refrigerator Thermistor
If the control senses an open or a shorted
thermistor, the air door and the evaporator fan
motor will begin to operate on a timed on and
off cycle, based on current selected tempera-
ture settings. The evaporator fan motor will run
when the air door is open.
At mid-settings of 37°F / 0°F, the air door will
open for 16 minutes, and close for 30 minutes.
Setting the freezer colder, or the refrigerator
warmer, will reduce the door-open time. Set-
ting the freezer warmer, or the refrigerator
colder, will increase the door-open time.