How It Works - Water Cooled - Scotsman CU1526 Service Manual

CU1526, CU2026, CU3030
Service Manual

How It Works - Water Cooled

Freeze Cycle. At start up the controller operates the water pump and purge valve to drain the reservoir.
The float valve refills the reservoir after the purge valve shuts off. 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 float valve will open to fill the reservoir anytime 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 open. An open curtain during
the harvest cycle signals the controller that the evaporator has released its ice and the controller will
terminate harvest. If the curtain remains open, the controller will shut the machine down. Anytime
harvest is complete the hot gas valve and harvest assist solenoid are shut off. The harvest assist
solenoid pin returns to its normal position by spring pressure.
If the curtain re-closes after harvest, the freeze cycle will restart
May 2008
Page 17