Sub-Zero UC-24 series Service Manual page 14

Electronic Control System
Regulate Refrigerator Zone Temperature (UC-24B, UC-24R, UC-24RO)
When the refrigerator compartment thermistor detects high off-set temperature, calling for cooling, the evaporator fan
is energized, but the compressor and condenser fan are not allowed to run until the thermistor on the evaporator
rises to 38°F (3°C). (See Figure 3-20)
If the door is opened while the evaporator fan is operating, the microprocessor will detect the power signal to the
lights and cut power to the fan.
NOTES:
• If compartment temperature exceeds either high or low offset the temperature display will change by one degree
(1°) per minute.
• If refrigerator com-
partment thermistor
is faulty, compressor
operation defaults to
twenty (20) minutes
ON, forty (40) min-
utes OFF cycling;
EE appears in right
of LCD; SERVICE
flashes and Error
Code 05 is logged.
• If evaporator ther-
mistor is faulty, the
compressor will not
energize until zone
air temperature
exceeds high offset
by 5°F (3°C); SER-
VICE flashes and
Error Code 06 is
logged.
• When in Sabbath
Mode, the refrigera-
tor compartment
thermistor still con-
trols compressor
operation, except
there is a random fif-
teen (15) to twenty-
five (25) second
delay before the
compressor is ener-
gized.
#7003933 - Revision B - November, 2007
LOW VOLTAGE SCHEMATIC
DISPLAY
4. Evap Thermistor
above 38°F (3°C).
1. Compartment thermistor at high
off-set temp. calling for cooling.
HIGH VOLTAGE SCHEMATIC
ORANGE
J2
P4
PIN 1
P3
MAIN BOARD
P1
P2
PIN 1
J6
J4
PIN 1
PIN 1
PIN 1
J3
J5
ORANGE
Figure 3-20. UC-24B Signal Trace - Regulate Refrigerator Zone
Under Counter (UC-24) Series
MEMBRANE KEYPAD
J2
PIN 1
DISPLAY BOARD
PIN 1
J3
BLUE W/RED STRIPE
THERMISTOR
ORANGE W/RED STRIPE
EVAPORATOR
BLUE W/BLACK STRIPE
BLUE W/BLACK STRIPE
THERMISTOR
REFRIGERATOR
115 VOLTS
60 CYCLES
LIGHT TUBE SWITCH
L1
NEUTRAL
WHITE
5. Compressor and con-
denser fan energized.
WHITE
BLACK
PURPLE
RED
3. Evap fan energized.
ORANGE
REF LIGHT
SWITCH
2. Door is closed, so no power to lights.
This is monitored via the orange wire.
3-14
J6
ORANGE
YELLOW
J4
RED
WHITE
J5
REF LIGHT SWITCH
WHITE
PINK
LIGHTS
(UC-24B ONLY)
OVERLOAD
PROTECTOR
COMPRESSOR
M
M
CONDENSER FAN
M
REF FAN MOTOR
REF (TOP)
LIGHT
J2
P4
PIN 1
P3
MAIN BOARD
P1
P2
PIN 1
PIN 1
PIN 1
PIN 1
J3
WHITE
RUNNING
CAPACITOR
(WHEN
USED)
COMPRESSOR
STARTING
RELAY