Viking VCSB48, Service Notebook

Page: 13 / 33

13
Electronic Functional Description ( con’t )
Adaptive Defrost Operation
Defrost occurs after predetermined length of
compressor run hours. Compressor run time 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 1 (8 hours) or CRTD 2 (12 hours) or
CRTD 3 (16 hours).
If defrost length is low (DT-LO defined as 21
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. Defrost 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
terminator opens before compressor and
condenser fan motor will operate. Ten minute
dwell time occurs after defrost terminator opens
before evaporator fan motor will operate. Dwell
time can be bypassed by disconnecting power to
the unit for 30 seconds.
•
Conventional defrost can be selected in Program
Mode B.
PROGRAM MODE
Accessing Program Mode
Two programming modes are available. Mode A
allows
reading refrigerator and freezer thermistor
temperatures. Mode B is used for all odther
programmable functions.
1. Open refrigerator door.
2. Press Display On pad.
3. Press Hidden Button pad.
4. Press the following sequence of pads within 6
seconds; Max Ref, Max Frz, Max Ref, Max frz.\
5. When access is granted, tone will sound three
times and control will be in Program Mode A.
unmarked indicator light will illuminate.
6. Toggle to Program Mode B be pressing Display
On pad. Unmarked indicator light is off.
EEPRM Update in Control Memory
EEPRM is permanent programmable memory of the
control pane..
•
Entry tone, door audio alarm and status are
stored in EEPRM after control panel is
deactivated.
•
Information stored in EEPRM memory is not
affected by power loss.
Mode A Functions
Reading Temperature Display
Temperature display will show thermistor
temperature in binary coded decimal format (BCD).
Indicator lights 1 through 4 represent the tens digit
with 1 being the most significant bit. Indicator lights
5 through 8 represent ones digit with 5 being the
most significant bit. Positive and negative are shown
be indicator light 9; light glows to show negative
value.