Scotsman CME506 Manual download pdf (Page 16)

Technicians Only: Freeze Cycle Operational Sequence

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

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 motor (air cooled only). Some

early units have a fan control switch, it shuts the

fan off if the discharge pressure drops below 190

PSIG. Machines built beginning in August 1996 do

not have a fan control switch, instead the

Controller checks the discharge temperature and

cycles the fan every 30 seconds if the temperature

is low (below 125

F. or more than 3381 ohms).

If the discharge temperature exceeds the design

maximum (250

F. or less than 377 ohms), 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

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 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 (38

F. or

27835 ohms). The pump will only be off for a few

seconds. After the pump restarts, the inlet water

valve opens to refill the reservoir.

7. As the machine makes ice, the water level in the

reservoir will ultimately fall to the Harvest Level

(when the top electric eye in the water level sensor

is disrupted by the adjustment screw).

Note: If the freeze cycle exceeds the preset

Maximum (50 minutes), the Controller will Shut

Down on a Refrigeration Error.

8. The end of Freeze cycle will see the machine in

this state:

•

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 Controller

switches the Harvest indicator light ON.

Note: If there is a power interruption, the system

controller will automatically restart the machine

with a process that begins with getting the

machine back to a normal state: water re-fills, the

unit freezes for 30 seconds and then goes into a 4

minute harvest. It will then proceed to a new

Freeze cycle. While in an electrical restart mode,

the controller’s Freeze light will be blinking - even

when the machine is in harvest.

CME256, 506, 656, 806: AutoIQ™ Cubers

January 2002

Page 16

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Scotsman CME506 Manual Page 16

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