Technicians Only: Freeze Cycle Operational Sequence - Scotsman SCE275 Serivce Manual

SCE275

Technicians Only: Freeze Cycle Operational Sequence

How The Electronic Cuber Works
This section is intended for the technician. It is not
necessary for the normal operation and
maintenance of the machine.
The AutoIQ Controller operates the ice machine by
monitoring several input measures and switching
various loads on and off.
Assuming the machine has been operational,
the Freeze cycle begins with the end of the
Harvest Cycle:
Reservoir is full
Condenser fan is OFF
Water Inlet Valve is OFF
Water Pump is ON
Compressor is ON
Hot Gas Valve is ON
AutoIQ Controller Operation, Beginning freeze:
1. Switches on the Freeze indicator light and shuts
off the hot gas valve.
2. Measures and stores the discharge temperature.
3. Starts the fan motors (air cooled only). Fan
control begins 4 minutes into the freeze cycle.
When the discharge temperature indicates that
cooler ambient conditions exist, the fan is cycled
on and off every 30 seconds until it is switched of
just before harvest.
If the discharge temperature exceeds the design
maximum, shuts the machine down on a
Refrigeration Error.
4. Checks for a "bin full" signal throughout the
cycle.
5. Measures the reservoir water temperature. If the
machine is operating correctly, the reservoir water
temperature will fall at a standard rate. The AutoIQ
Controller will be checking to see if the water
temperature fall matches that rate.
If not, it re-checks the discharge line temperature.
If too low, it Shuts Down on a Refrigeration Error. If
the discharge temperature is acceptable, the water
system is checked by shutting off the water pump
and determining if the water level goes up enough.
If it does not, it is assumed that there is a water
pump problem and the machine Shuts Down on a
Water Error.
If the water level does "measure up" the water
pump is restarted and the AutoIQ Controller then
measures how long it takes to lower the water
level. If the water level does not fall, the machine
Shuts Down on a Water Error.
6. Once per cycle the machine may shut off the
water pump. It only does this when the water
temperature reaches a preset minimum. The pump
will only be off for a few seconds. After the pump
restarts, the inlet water valve opens to refill the
reservoir.
7. When the water level falls to the pre-set limit, the
inlet water valve will open to refill the reservoir.
This happens 2 times every freeze cycle.
8. As the machine makes ice, the water level in the
reservoir will ultimately fall a third time to the
Harvest Level (when the top electric eye in the
water level sensor is disrupted by the adjustment
screw). At that point, the fan may be shut off and
the unit continues in a freeze cycle for a few more
seconds (0-60 depending upon discharge
temperature). Note: If the freeze cycle exceeds the
preset Maximum of 35 minutes, the AutoIQ
Controller will Shut Down on a Refrigeration Error.
9. The end of Freeze cycle will see the machine in
this state:
Water level = below harvest position
Condenser fans will be off
Water inlet valve will be off
Water pump will be ON
Compressor will be ON
Hot gas valve will be off
At this point Harvest begins and the AutoIQ
Controller switches the Harvest indicator light ON.
Note: If there is a power interruption, the AutoIQ
Controller will automatically restart the machine
with a process that begins with returning the
machine back to a normal state: water re-fills the
reservoir, the unit freezes for 30 seconds, and then
goes thru a 4 minute harvest. After harvest it
returns to a new Freeze cycle. While in this
electrical restart mode, the controllers Freeze light
will be blinking, even when it is in a Harvest cycle.
January 2003
Page 18