Technicians Only: Freeze Cycle Sequence - Scotsman CME1856W User Manual

CME1856W

Technicians Only: Freeze Cycle Sequence

Assuming the machine has been operational, the
Freeze cycle begins with the end of the Harvest
Cycle:
•
Water Inlet Valve is Closed
•
Water Pump is ON
•
Compressor is ON
•
Hot Gas Valve is Open
System Controller Operation, Beginning freeze:
1. Switches on Freeze indicator light and shuts off
the hot gas valve.
2. Opens the water valve to top off the reservoir.
The controller checks that water fills the reservoir,
if it does not fill up within 250 seconds, the
controller shuts the machine down. It will
automatically try to restart in 20 minutes.
3. Measures and stores the discharge
temperature.
4. If the discharge temperature exceeds the design
maximum, shuts the machine down on a
Refrigeration Error.
5. Checks for a "bin full" signal throughout the
cycle.
6. Measures the reservoir water temperature. If the
machine is operating correctly, the reservoir water
temperature will fall at a standard rate. The
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, the inlet water valve will open again
to fill it. If, after restarting, the water level does not
drop, 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 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.
7. Once per freeze cycle the machine will 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.
8. As the machine makes ice, the water level in the
reservoir will ultimately fall to the Harvest Level.
The first time that happens per freeze cycle the
inlet water valve is re-opened and the reservoir is
refilled. The next time it happens, the unit will go
into a harvest cycle.
Note: If the freeze cycle exceeds the preset
Maximum (36 minutes), the Controller will Shut
Down the machine and switch on the Refrigeration
Light.
9. The end of Freeze cycle will see the machine in
this state:
•
Water level = below harvest position
•
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 System
Controller switches the Harvest indicator light ON.
Restarts:
If the machine is restarting after it has shut off
because the bin was full, the first freeze cycle
sequence is like this:
1. Purge valve is open.
2. Pump starts.
3. Purge valve closes.
4. Water valve opens to fill the reservoir.
5. Compressor starts.
Note: If there is a power interruption, after power is
restored the machine will restart, go thru a brief
Freeze cycle and go thru a 6 minute Harvest cycle.
Error Restarts:
The machine automatically attempts to restart 50
minutes after a shut down. If another problem
occurs in the next cycle, the machine will attempt
one more restart. If another problem occurs in the
next cycle, the machine will shut off and must be
manually reset.
November 2001
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