Sub-Zero INTEGRATED Series Service Manual page 21

General Information
Monitor and Control Freezer "Adaptive Defrost"
Initially the freezer compressor will cycle-run for twelve hours (twenty-four hours in the model 736TFI), after which
the microprocessor sends the signal to the defrost relay on the control board to close. This supplies power to the
defrost heater, and the compressor is switched off
length of time that the heater actually stays on to defrost the evaporator and satisfy the defrost terminator is
observed by the microprocessor. The microprocessor then determines the number of hours before the next defrost.
If the heater stays on for a shorter time than estimated, the microprocessor increases the next defrost interval. If the
heater stays on longer than estimated, the electronic control decreases the next defrost interval. This is an ongoing
process whereby the defrost time and the defrost interval will vary by unit use.
NOTES:
• A five (5) minute time delay/dwell follows all defrosts, except in the model 736TFI where the delay/dwell is ten
(10) minutes. The drain trough heater is energized during defrost and the delay/dwell period.
• The minimum defrost interval is six (6) hours; The maximum defrost interval is eighty (80) hours; the maximum
defrost duration is twenty-five (25) minutes.
• If the defrost sensing line is open, defrost operation defaults to 25 minute defrost time / 6 hour build time, and
Error Code 22 is logged. If the evaporator thermistor detects an under-heat or overheat situation at the same
time, Error Codes 20 or 23 is logged, respectively.
• During defrost, the displayed temperature is locked.
HIGH VOLTAGE
BLACK
J5
J7
E2 E7 E10 E6
J4
J3
J1
J2
Figure 3-22. 736TCI Signal Trace Schematic (High Voltage) of Freezer Adaptive Defrost
#7015817 - Revision A - January, 2010
INTEGRA
INTEGRA
L1
115 VOLTS
NEUT
60 CYCLES
WHITE
J6
Length of defrost time
monitored by micro-
processor via defrost
sense line
GRAY/WHITE
DEFROST
BLUE TERMINATOR
TED
TED
(736 T (736 T all SWS #2970000) all SWS #2970000)
(See Figure 3-22). With the "Adaptive Defrost" technique, the
WHITE
3
1
5
4
6
2
7 8
M
3-14
SERIES
SERIES
M
M
M
M
Defrost heater energized
& monitored
DEFROST
30-38 Ω
HEATER
155-175 Ω
DRAIN TROUGH
HEATER
Drain trough heater
also energized dur-
ing defrost and
delay/dwell period