Mode A And Mode B - Viking VCSB483D Service Notebook

Electronic Functional Description (con't)
1. Critical temperature for freezer is +15° F; for
refrigerator critical temperature is +60° F.
2. Press Alarm Off pad to turn off alarm.
Thermistor Alarm
Alarm sounds and freezer or refrigerator indicator
light shows and temperature indicators 4 through 7
will turn on in sequence if either thermistor circuit
opens. Refer to Temperature Control Operation
Section and Electronic Testing Section.
1. Press Alarm Off pad to turn off alarm.
2. Alarm will retest for normal operation.
condition has not been corrected, alarm will
sound again.
Temperature Control Operation
For any temperature setting, outputs will be turned
off/on based on
determined by resistance levels of freezer and
refrigerator thermistors.
Refrigerator and Freezer Thermistor
(See page 24, Item A)
As temperature decreases, resistance increases.
As temperature increases, resistance decreases.
Open thermistor or thermistor circuit will
result in failure of refrigerator to cool.
Shorted thermistor will cause refrigerator to
run 100 percent of time except for defrost cycle.
•
Freezer temperature setting and thermistor
value will determine if compressor/condenser
fan and evaporator fan switches are open or
closed. Compressor/condenser fan switch
must be open for 6 minutes before switch can
close again (compressor dwell time).
•
Refrigerator temperature
thermistor value will determine if fresh food
fan switch is open or closed.
•
Cut-out and cut-in temperature values must be
reached and maintained for 15 seconds before
output state will change (digital delay).
•
Refrigerator and freezer control calibration
can be adjusted in Program Mode B.
Factory set freezer and refrigerator settings
(See page 24. Item B)
cut-in/cut-out temperature
setting
Adaptive Defrost Operation
Defrost occurs after predetermined length of
compressor run hours.
between defrosts changes, or adapts, depending
upon recent history of defrost lengths (time it
takes for defrost terminator to open after defrost
heater has been turned on).
•
Defrost terminator opens at 55° F (13° C)
and closes at 20° F (-7° C).
•
Compressor run time between defrost
(CRTD) will be one of 3 values under
normal operation:
CRTD 2 (12 hours) or CRTD 3 (16 hours).
If defrost length is low (DT-LO defined as 21
If
minutes) indicating small frost load, CRTD for
next defrost cycle is advanced to next level.
If defrost length is high (DI-HI defined as 24
minutes) indicating large frost load, CRTD for
next defrost cycle is lowered to next level.
If defrost length is between 21 and 24 minutes,
CRTD for next defrost cycle remains the same.
Initial value at power up CRTD 0 is 4 hours.
•
Hidden Button (*) Mode CRTD equals 96
hours. Hidden Button (*) Mode CRTD is
interrupted with door openings.
interval will revert back to interval before
Hidden Button (*) Mode. Three things must
occur to reach Hidden Button Mode (*)
CRTD:
1. Defrost interval must be CRTD 3 (16
hours).
2. Both refrigerator and freezer doors must
have remained closed since last defrost
cycle.
3. Defrost thermostat must have opened in
less than 21 minutes during last defrost
cycle.
•
Six minutes dwell time occurs after defrost
and
terminator opens before compressor and
condenser fan motor will operate.
minute dwell time occurs after defrost
terminator opens before evaporator fan
motor will operate.
bypassed by disconnecting power to the unit
for 30 seconds.
•
Conventional defrost can be selected in
Program Mode B.
21
Compressor run time
CRTD 1 (8 hours) or
Defrost
Ten
Dwell time can be