Monitor, Regulate And Display Freezer Compartment Temperatures - Sub-Zero Wolf BI Series Service Manual

Electronic Control

Monitor, Regulate and Display Freezer Compartment Temperatures

Temperature signals from the freezer compartment thermistor are monitored by the microprocessor. When the
freezer compartment thermistor detects high offset temperature, calling for cooling, the freezer compressor is cycled
ON and in most cases the evaporator fan motor receives a high-speed run command, switching it ON. However, if
the freezer is calling for cooling following a defrost, the evaporator fan will not be switched ON until the freezer evap-
orator falls to 35°F (2°C). When the compartment reaches low offset temperature, the compressor and evaporator
fan are switched OFF. Though compartment air temperature fluctuates from OFF and ON cycles, it is the freezer
compartment's "average" tem-
perature that is displayed at the
left side of the LCD. (See
Figure 2-44)
NOTES:
• Freezer zone temperature
range is -5°F (-21°C) to +5°F
(-15°C)
• If average compartment tem-
perature changes, the display
will change by one degree
per minute.
• When high offset is detected
after a defrost, the freezer
compressor will not be ener-
gized until after the five (5)
minute time delay/dwell that
follows all freezer defrosts.
• If a freezer compartment
thermistor is faulty, the freez-
er compressor defaults to 20
minutes ON, 20 minutes OFF
cycling, EE appears at left in
LCD, the service icon flashes
and the appropriate fault
code is logged.
• If a freezer evaporator ther-
mistor is faulty, the freezer
compressor will be energized
immediately after the five (5)
minute dwell and the evapo-
rator fan motor will be ener-
gized three (3) minutes later,
the service icon flashes and
the appropriate fault code is
logged.
• If in Sabbath Mode, the com-
partment thermistor still
controls compressor oper-
ation, except that when
high offset is reached,
there is a random 15 to 25
second delay before the com-
pressor is energized.
• The condenser fan is ener-
gized whenever a compres-
sor is energized.
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
LOW VOLTAGE
1 NEUTRAL
4 L1
6 L1
1 MAIN LIGHTS
3 COMP 1
5 COMP 2
8 DEFROST HTR
Average temp.
displayed at
Left of LCD
EXTERNAL
DEVICE
KEYPAD
Figure 2-44. Signal Trace Schematic: Regulating Freezer Temperature
(SWS #4380000)
(SWS #4380000)




3. Condenser fan
energized







 

 








2. Compressor energized



1

17

1



6



1

16
1. Freezer's high offset temperature detected
2-28


660 Ω

160 Ω










2300-2900 Ω

27.9-30.9 Ω




5. Run command
sent to evapo-
rator fan









4. Freezer evapo-
rator below

35°F (2°C)





















