Manitowoc Marine Q 1000, Service Technician'S Handbook

Page: 61 / 179

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Ice Thickness Probe (Harvest Initiation)
HOW THE PROBE WORKS
Manitowoc’s electronic sensing circuit does not rely on
refrigerant pressure, evaporator temperature, water
levels or timers to produce consistent ice formation.
As ice forms on the evaporator, water (not ice)
contacts the ice thickness probe. After the water
completes this circuit across the probe continuously
for 6-10 seconds, a Harvest cycle is initiated.
HARVEST/SAFETY LIMIT LIGHT
This light’s primary function is to be on as water
contacts the ice thickness probe during the freeze
cycle, and remain on throughout the entire harvest
cycle. The light will flicker as water splashes on the
probes.
The light’s secondary function is to continuously flash
when the ice machine is shut off on a safety limit, and
to indicate which safety limit shut off the ice machine.
FREEZE TIME LOCK-IN FEATURE
The ice machine control system incorporates a freeze
time lock-in feature. This prevents the ice machine
from short cycling in and out of harvest.
The control board locks the ice machine in the freeze
cycle for six minutes. If water contacts the ice
thickness probe during these six minutes, the harvest
light will come on (to indicate that water is in contact
with the probe), but the ice machine will stay in the
freeze cycle. After the six minutes are up, a harvest
cycle is initiated. This is important to remember when
performing diagnostic procedures on the ice thickness
control circuitry.
To allow the service technician to initiate a harvest
cycle without delay, this feature is not used on the first
cycle after moving the toggle switch OFF and back to
ICE.