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DEFROST SYSTEM
Adaptive Defrost
Adaptive Defrost can be described as a defrost
system that adapts to a refrigerator’s
surrounding environment and household usage.
Unlike conventional defrost systems that use
electromechanical timers with a fixed defrost
cycle time, Adaptive Defrost utilizes an
intelligent, electronic control to determine when
the defrost cycle is necessary. In order to
accomplish the correct defrost cycle time, the
main control board monitors the following
refrigerator operations:
•
Length of time the refrigerator doors were
open since the last defrost cycle
•
Length of time the compressor has run
since the last defrost cycle
•
Amount of time the defrost heaters were on
in the last defrost cycle
Adaptive Defrost is divided into 5 separate
cycles. Those operations are:
•
Cooling Operation
•
Pre-Chill Operation
•
Defrost Heater Operation
•
Dwell Period
•
Post Dwell
(See Pub. #31-9062 for more information on
Adaptive Defrost.)
Adaptive Defrost (Cooling Operation)
During the cooling operation, the main control
board monitors door opening (fresh food and
freezer doors) and compressor run times. The
board counts the time the doors are open. It
reduces the length between defrosts by 210
seconds (multiplication factor) for each second
that each door is open (if both doors are open,
it reduces it by twice the amount). The
multiplication factor reduces compressor run
time. If the doors are not opened, the
compressor will run up to 60 hours between
defrosts. If the doors are opened frequently
and/or for long periods of time, the compressor
run time between defrosts will be reduced to as
little as 8 hours.
Adaptive Defrost (Pre-chill Operation)
09:00
10:00
11:00
12:00
13:00
14:00
15:00
16:00
17:00
18:00
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Defrost
Pre-Chill
08:00
25˚ / -4˚
20˚ / -7˚
15˚ / -9˚
10˚ / -12˚
5˚ / -15˚
0˚ / -18˚
-5˚ / -21˚
-10˚ / -23˚
-15˚ / -26˚
-20˚ / -29˚
F˚ / C˚
PRE-CHILL MODE
When the main control board determines that
defrost is necessary, it will force the refrigerator
into a continuous cool mode (pre-chill). During
pre-chill, the freezer temperature may be driven
below the set point. However, the fresh food
temperature will be regulated by the evaporator
fan running at low speed. Pre-chill will last for 2
hours. These models do not have a defrost
holdoff.
Adaptive Defrost (Defrost Heater
Operation)
After 2 hours of pre-chill operation, the main
control board turns off the compressor,
condenser fan, and evaporator fan.
During defrost operation, the main control board
monitors the evaporator temperature using
evaporator thermistor inputs. Typically, the
evaporator thermistor will sense a temperature
of 65°F within 25 minutes. When the thermistor
senses 65°F, the main control board will
terminate defrost heater operation. Maximum
defrost cycle (heater on) time is 45 minutes
(main control board time out).
The defrost system is protected by a defrost
termination thermostat (switch). The thermostat
opens when the evaporator temperature raises
to 140°F and closes when the evaporator
temperature lowers to 110°F.
