How It Works - Remote
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 liquid line valve, compressor
and water pump are switched on. After the discharge pressure has increased past the set point
of the headmaster in the condenser, the headmaster will direct refrigerant gas into the
condenser and warm air will be discharged out of the condenser. The headmaster will
modulate to maintain a minimum 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. 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(s) re-close after harvest, the freeze cycle will restart.
Shut down occurs when a curtain remains open after a harvest cycle. The controller will switch
off the liquid line solenoid valve and operate the compressor for 30 seconds, then shut it off.
November 2006 Page 26
