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MC0322 through MC2148
Air, Water, and Remote Cooled Service Manual
Electrical Sequence - Air or Water Cooled
Power connected, unit previously switched Off.
Control board does a self check. If the self check fails, the unit displays an E and no further action will occur.
If the self check passes, the controller will display a 0, the curtain light(s) will be ON and the Power and Sump
Empty lights will be ON.
Pushing and releasing the On button will start the ice making process.
The display will begin to blink F. The component indicator lights will switch on and off to match the following
process:
The purge valve opens and the water pump starts to empty the reservoir. This is done to discharge any excess
water from ice melting into the reservoir.
The hot gas valve and the harvest assist solenoid are energized.
The inlet water valve will open to fill the reservoir. The water valve can open any time the water level is low.
After a few seconds the purge valve closes and the pump shuts off.
When the reservoir is full the inlet water valve stops and the compressor switches on. Five seconds after the
compressor starts the hot gas valve and the harvest assist solenoid are de-energized.
Light Information: The display shows a non-blinking F. The Power and Status Lights will be Green. The
compressor, fan motor, water pump, sump full and one or two curtain switch lights will be ON.
The air cooled model's fan motor will start to turn when the discharge pressure has built up to the fan pressure
control's cut in point. This is about 15 seconds after the compressor starts.
The Freeze cycle continues. The compressor, water pump, fan motor and curtain indicator lights will be
ON. When the reservoir water temperature falls to a certain preset point, the water pump will shut off for 30
seconds. This is the anti-slush period. At this time the controller checks the conductivity of the water in the
reservoir for the auto-purge feature. After the water pump restarts the Sump Full light will go out and neither
sump lights will be on for the rest of the freeze cycle.
When the ice has built up enough so that the water flowing over the evaporator comes into continuous contact
with the ice level sensor, the Ready to Harvest light will begin to blink on and off. When it has been On
continuously for 5 seconds, the controller will switch the machine into a Harvest cycle.
Indicator Information: The display shows a non-blinking H. The Power and Status Lights will be Green. The
compressor, hot gas valve and one or two curtain switch lights will be ON. After a few seconds the water pump,
purge valve and inlet water valve lights will come on.
The fan motor(s) shut off and remain off throughout the harvest cycle.
The harvest assist solenoid is connected in parallel with the hot gas valve. Although it is energized throughout
the harvest cycle, its piston does not move until the ice has become partially loosened from the evaporator
plate by the action of the hot refrigerant gas passing through the evaporator serpentine.
The water pump and purge valve will shut off when the purge level setting time has been reached, either the
manual time or the automatic time. The inlet water valve will remain on until it fills the reservoir. The Ready to
Harvest light will switch Off when the ice falls from the evaporator.
Harvest continues until the ice slab is ejected from the evaporator and falls, opening the curtain. When the
curtain opens, the magnetic reed curtain switch opens, breaking the circuit to the controller. If the curtain re-
closes within 30 seconds, the controller switches the machine back into another freeze cycle. If the curtain
switch remains open, the controller shuts the machine down and puts it into a standby position.
January 2022
Page 20
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