Monitor And Control “Adaptive Defrost” Of Freezer Evaporator - Sub-Zero Wolf BI Series Service Manual

Electronic Control
Monitor and Control "Adaptive Defrost" of Freezer Evaporator
Initially, the freezer compressor cycle-runs for six (6) hours, then the compressor and evaporator fan are switched
OFF and the control board defrost relay is closed, supplying power to the defrost heater.
With "Adaptive Defrost", the length of time the defrost heater stays on to open the defrost terminator bimetal is
observed by the microprocessor via the grey w/white stripe wire to P18-6. This length of time is used to calculate
the number of hours before the next defrost (defrost interval). If the heater is energized for a shorter time period
then the microprocessor estimated based on predetermined algorithms, the microprocessor increases the next
defrost interval. If the heater stays on for a longer time period, the microprocessor decreases the next defrost inter-
val. (See Figure 2-46) This is an ongoing process whereby the defrost heater ON-time and the defrost interval will
vary by unit use.
NOTES:
• A five (5) minute time delay/dwell follows all defrosts, before the compressor is energized.
• Minimum defrost interval = 6 hours of compressor run time; Maximum defrost interval = 80 hours of compressor
run time; Maximum defrost duration = 30 minutes, plus 5 minute dwell.
• If the defrost sensing line to P18-6 is open, defrost operation defaults to 25 minute defrost heater ON-time / 6 hour
build-time, and the appropriate fault code is logged.
• During defrost, the displayed freezer temperature is locked.
2. Elapsed time from
heater ON state to
terminator opening
is monitored via
Grey/White Wire to
P18-6, then interval
before next defrost
is determined and
set
7040317 - Revision A - September, 2015
Built-In (BI) Series
Built-In (BI) Series
HIGH VOLTAGE






1 NEUTRAL
4 L1
6 L1
1 MAIN LIGHTS
3 COMP 1
5 COMP 2
8 DEFROST HTR
9
1
6
1

Figure 2-46. Signal Trace Schematic: Freezer Adaptive Defrost
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
 





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
1. Defrost heater
Energized

2-30
(SWS #4380000)
(SWS #4380000)


660 Ω

160 Ω










2300-2900 Ω

27.9-30.9 Ω







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