Electronic Control System
Under Counter (UC-24) Series
3-14
#7003933 - Revision B - November, 2007
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.
Figure 3-20. UC-24B Signal Trace - Regulate Refrigerator Zone
1. Compartment thermistor at high
off-set temp. calling for cooling.
4. Evap Thermistor
above 38°F (3°C).
3. Evap fan energized.
2. Door is closed, so no power to lights.
This is monitored via the orange wire.
5. Compressor and con-
denser fan energized.
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