Manitowoc QD0202A, Service Manual

Page: 125 / 175

Section 7 Refrigeration System
Part No. 80-1100-3
7-13
SAFETY LIMITS
General
In addition to standard safety controls, such as high
pressure cut-out, the control board has two built in safety
limit controls which protect the ice machine from major
component failures. There are two control boards with
different safety limit sequences. Original production
control boards have a black micro-processor. Current
production and replacement control boards have an
orange label on the control board microprocessor.
Safety Limit #1: If the freeze time reaches 60 minutes,
the control board automatically initiates a harvest cycle.
Control Board with black microprocessor
If 3 consecutive 60-minute freeze cycles occur, the ice
machine stops.
Control Board with orange label on microprocessor.
If 6 consecutive 60-minute freeze cycles occur, the ice
machine stops.
Safety Limit #2: If the harvest time reaches 3.5
minutes, the control board automatically returns the ice
machine to the freeze cycle.
Control Board with black microprocessor
If three consecutive 3.5 minute harvest cycles occur, the
ice machine stops.
Control Board with orange label on microprocessor.
If 500 consecutive 3.5 minute harvest cycles occur, the
ice machine stops.
Safety Limit Indication
Control Board with Black Microprocessor
When a safety limit condition is exceeded for 3
consecutive cycles the ice machine stops and the
harvest light on the control board continually flashes on
and off. Use the following procedures to determine
which safety limit has stopped the ice machine.
1. Move the toggle switch to OFF.
2. Move the toggle switch back to ICE.
3. Watch the harvest light. It will flash one or two times,
corresponding to safety limits 1 and 2, to indicate
which safety limit stopped the ice machine.
After safety limit indication, the ice machine will restart
and run until a safety limit is exceeded again.
Control Board with Orange Label
When a safety limit condition is exceeded for 3
consecutive cycles the control board enters the limit into
memory and the ice machine continues to run. Use the
following procedures to determine if the control board
contains a safety limit indication.
1. Move the toggle switch to OFF.
2. Move the toggle switch back to ICE.
3. Watch the harvest light. If a safety limit has been
recorded, the harvest light will flash one or two
times, corresponding to safety limit 1 or 2.
When a safety limit condition is exceeded (6 consecutive
cycles for Safety Limit #1 or 500 cycles for Safety Limit
#2) the ice machine stops and the harvest light on the
control board continually flashes on and off. Use the
following procedures to determine which safety limit has
stopped the machine.
1. Move the toggle switch to OFF.
2. Move the toggle switch back to ICE.
3. Watch the harvest light. It will flash one or two times,
corresponding to safety limit 1 or 2 to indicate which
safety limit stopped the ice machine.
After safety limit indication, the ice machine will restart
and run until a safety limit is exceeded again.
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