How It Works - Water Cooled - Scotsman Prodigy Elite MC0322 Service Manual

MC0322 through MC2148
Air, Water, and Remote Cooled Service Manual

How It Works - Water Cooled

Freeze Cycle. At start up the controller drains and refills the reservoir. The reservoir refills when the mid length
water level sensor probe is uncovered and continues to fill until the top probe is in contact with water. When the
reservoir has filled, the compressor and water pump start. After the discharge pressure has increased past the
set point of the water regulating valve, the water regulating valve will open and warm water will be discharged
out the condenser drain. The water regulating valve will modulate to maintain a relatively constant discharge
pressure. Water flows over the evaporator as the refrigeration system begins to remove heat. When the water
temperature falls to a preset point, as measured by the water temperature sensor, the controller shuts off the
water pump for 30 seconds. The freeze cycle resumes when the pump restarts and ice begins to form on
the evaporator. As it forms, the water flowing over the ice moves closer and closer to the metal tip of the ice
thickness sensor. When it comes into contact with the sensor for a few continuous seconds, that signals the
controller that the freeze cycle is complete.
Harvest Cycle. When the harvest cycle begins, the controller switches on the hot gas valve, and through a
parallel circuit, the harvest assist solenoid. After a few seconds the purge valve opens and water is drained
from the reservoir. Based on either the automatic purge or manual purge setting, the pump and purge valve
will be switched off at a time determined to have drained enough water for that setting. The inlet water valve
will open to fill the reservoir anytime the mid length probe is uncovered, which occurs during the reservoir drain
cycle.
Harvest continues as the hot discharge gas flows into the evaporator serpentine, heating up the evaporator. At
the same time the harvest assist solenoid is pushing against the back of the ice slab. When the ice releases
from the evaporator, it harvests as a unit, and the harvest assist probe provides some additional force to push
it off. When the ice falls off it will force the curtain(s) open. An open curtain during the harvest cycle signals
the controller that the evaporator has released its ice. If this is a single evaporator machine the controller will
terminate harvest. If it is a two evaporator machine, the controller will continue harvest until both curtains have
opened. If a curtain remains open, the controller will shut the machine down on bin full. Anytime harvest is
complete the hot gas valve and harvest assist are shut off. The harvest assist pin returns to its normal position
by spring pressure.
If the curtain(s) re-close after harvest, the freeze cycle will restart.
January 2022
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