Scotsman CME306 - Manual (Page 23)

Technicians Only: Freeze Cycle Operational Sequence
Assuming the machine has been operational, the
Freeze cycle begins with the end of Harvest:
• Condenser fan is OFF
• Water Inlet Valve is CLOSED
• Water Pump may be ON
• Compressor is ON
• Hot Gas Valve is OPEN
The Controller, from the start of the freeze
cycle:
1. Switches on the Freeze indicator light and shuts
off the hot gas valve.
2. Opens the water valve to top off the reservoir.
Water must fill the reservoir within 130 seconds or
the controller shuts the machine down. It will
automatically try to restart in 20 minutes.
3. Measures the discharge temperature.
4. Starts the fan motor (air cooled only). The
Controller checks the discharge temperature and
cycles the fan(s) on every 12 seconds and off for
20 seconds (CME456) or 45 seconds (CME306) if
the temperature is low.
If the discharge temperature exceeds the design
maximum the controller shuts the unit off.
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 stops the unit. 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 controller shuts the unit off.
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.
7. Once per 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. After the pump
restarts, the inlet water valve opens to refill the
reservoir.
8. As the machine makes ice, the water level in the
reservoir will ultimately fall to the Harvest Level .
• CME306 fills the reservoir once at the
beginning of Freeze
• CME456 fills the reservoir at the beginning
of freeze and one more time about ½ way
through freeze.
Air cooled models will switch off the fan motor a
few seconds before harvest begins.
Note: If the freeze cycle exceeds the preset
Maximum (45 minutes), the Controller will shut the
unit off.
9. At the end of Freeze cycle:
• Water level = below harvest position
• Condenser fan 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.
Restarts:
If restarting after shutting 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 then go thru a 5 minute Harvest
cycle. The Freeze light will be blinking - even when
the machine is in harvest.
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 be off and must be
manually reset.
CME306 & CME456
January 2000
Page 23