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Electronic Control System
600 Series
(Prior to #1810000)
Monitor and Control Rerigerator Off-cycle Defrost
Temperature signals from the refrigerator compartment
thermistor and evaporator thermistor are monitored by
the microprocessor. If the compartment temperature
reaches high offset before the evaporator rises to 38°F,
the command to start the compressor will wait, allowing
the evaporator to fully defrost before the compressor is
energized. (See Figure 3-13)
Monitor and Control Freezer "Adaptive Defrost"
Initially the freezer compressor in a 600 Series unit will
cycle-run for 12 hours, after which the microprocessor
sends the signal to the defrost relay on the control
board to close. This supplies power to the defrost
heater, and the compressor is switched off. (See
Figure 3-14) With the "Adaptive Defrost" technique, the
length of time that the heater actually stays on to
defrost the evaporator and satisfy the defrost terminator
is observed by the microprocessor. The microproces-
Figure 3-13. Refrigerator Compressor OFF
sor then determines the number of hours before the
next defrost. If the heater stays on for a shorter time
than specified, the microprocessor increases the next
defrost interval. If the heater stays on longer than spec-
ified, the electronic control decreases the next defrost
interval. This is an ongoing process whereby the
defrost time and the defrost interval will vary by unit
use.
NOTE: A five (5) minute delay/dwell follows all defrosts.
NOTE: Minimum defrost interval = six (6) hours;
Maximum defrost duration = twenty-five (25) minutes.
Initiating Freezer Manual Defrost
To manually initiate freezer evaporator defrost, press
and hold the ICE key at the control panel for ten sec-
onds. (See Figure 3-15).
NOTE: To observe the initiation of manual defrost,
"ICE" must be displayed on the LCD. Then press and
hold the ICE key for ten seconds. At first, "ICE" will dis-
appear. After ten seconds of holding the ICE key, "ICE"
will appear again, indicating manual defrost has begun.
Figure 3-14. Defrost Heater Signal Trace
ICE
Figure 3-15. Push and Hold ICE Key for 10 Seconds to initiate Manual Defrost
3-10
#3756270 - Revision B - January, 2006
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Troubleshooting
