Manitowoc b970 series, Technician'S Handbook

Page: 113 / 264

Part Number STH025 8/12 113
Troubleshooting
Safety Limits
In addition to standard safety controls, the control
board has built in safety limit controls which protect the
ice machine from major component failures.
Safety limits are stored and indicated by the control
board. The number of cycles required to stop the ice
machine varies for each safety limit.
•
Safety Limit 1
- If the freeze time reaches 60
minutes, the control board automatically initiates a
harvest cycle. 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. If 500
consecutive 3.5 minute harvest cycles occur, the
ice machine stops.
SAFE OPERATION MODE
Allows the ice machine to operate up to 72 hours if the
ice thickness probe (E19 fault) and/or water level
probe sensors fail (E20 fault).
•
When the control board starts the safe mode an
alert is flashed on the LCD display to notify the
end-user they have a production problem.
• The control board automatically initiates and
monitors the safe mode. The control will
automatically exit the safe mode if a normal signal
is received from the input.
• After 72 hours the control board will enter a
standby mode and turn off
NOTE: The control board needs a five cycle history to
operate safe mode. If five cycles have never been
successfully completed the ice machine will shut-off.