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

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

How It Works - Air 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
cut in point of the fan pressure control, the fan motor(s) will begin to operate and warm air will be discharged
out the back of the cabinet. The fan motor will switch on and off as the discharge pressure rises and falls.
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.
The controller may shut the air cooled fan motor off for a variable period of time to build up heat for harvest.
This is dependant upon the temperature of the discharge line sensor.
Harvest Cycle. When the harvest cycle begins, the controller shuts off the fan motor, 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 one 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
Page 17