COMPONENT INFORMATION
2-13
DEFROST SYSTEM
Models 700TC/I, TF/I, BF/I
The electronic control in the 700TC/I, TF/I, BF/I
regulates defrost intervals with what is called
"Adaptive Defrost." With adaptive defrost, the
length of time that the heater actually stays on to
defrost the evaporator and satisfy the defrost ter-
minator is sensed by the evaporator thermistor.
The length of heater ON time determines the num-
ber of hours before the next defrost. For instance,
if the heater stays on for a shorter time than nor-
mal, the electronic control increases the time
between the next defrost. If the heater stays on for
a longer time than normal, the electronic control
decreases the time between the next defrost. This
is an ongoing process whereby the defrost time
and the defrost interval will vary by unit use.
NOTE: To initiate a manual defrost, turn OFF
master power switch for 10 seconds then turn back
ON. The control will initiate defrost upon power
up, provided the evaporator temperature is below
20°F. If the evaporator is warmer than 20°F, the
evaporator thermistor must be disconnected before
initiating defrost.
NOTE: If the evaporator thermistor fails, the elec-
tronic control will initiate defrost at 6 hour inter-
vals and 20 minute defrost dwell. To test the evap-
orator thermistor, refer to Troubleshooting Guide.
Models 700TR, 700BR
Since the 700TR and 700BR do not have defrost
heaters, the evaporator defrosts during the com-
pressor off cycle. If the compartment thermistor
calls for cooling, but the evaporator thermistor is
not sensing temperatures greater than 40°F, the
evaporator fan will be energized but the compres-
sor will not. This ensures complete evaporator
defrost. As soon as the evaporator temperature
reaches 40°F, the compressor is also energized.
NOTE: If the evaporator coil is iced up and the
compressor does not start, check the evaporator
thermistor and replace if faulty. To test the evapo-
rator thermistor, refer to the Trouble Shooting
Guide.
LIGHTING
The 700 Series utilizes Halogen lamps for interior
lighting.
Power for the lights is supplied through a 12 volt
transformer, which is controlled by a 5 volt circuit
through a relay on the control board. This 5 volt
circuit consists of the reed switches behind each
drawer, the sensor behind the control panel
(700TR, 700TC/I, 700TF/I only), the microproces-
sor and relays on the control board. When the
microprocessor senses an "open door" signal from
a reed switch or the sensor behind the control
panel, power is relayed to the 12 volt transformer
which then supplies power to the lighting in the
appropriate compartment.
If the lights in the upper compartment of the
700TR, 700TC/I, or 700TF/I get too hot, a thermal
cut-out in the upper control panel will interrupt
power to lighting system. The lighting system will
not operate until the lights cool back down.
NOTE: There is no light terminator in the drawer
area of 700 Series units.
CAUTION
Do not touch lamp with bare hands. Oils from
skin will reduce the life of the lamp. If lamp is
touched with bare hands, clean lamp with
denatured alcohol and wipe dry with lint free
cloth.
WARNING
Halogen lamps are extremely hot! Allow lamp
to cool before attempting to handle.
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