Ice Thickness Probe - Manitowoc Q270 Technician's Handbook

Ice Thickness Probe

How The Probe Works
Manitowoc's electronic sensing circuit does not rely on
refrigerant temperature, 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.
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
ON.
Maximum Freeze Time
The control system includes a built-in safety, which will
automatically cycle the ice machine into harvest after
60 minutes in the freeze cycle.
Part Number STH039 8/13 89