Operation; Ice Making Sequence Of Operation; Initial Start-Up Or Start-Up After Automatic Shut-Off; Freeze Sequence - Manitowoc QM45 Instructions D'installation

Ice Making Sequence of Operation

INITIAL START-UP OR START-UP AFTER

AUTOMATIC SHUT-OFF

1. Pressure Equalization
Before the compressor starts the hot gas valve is
energized for 15 seconds to equalize pressures during
the initial refrigeration system start-up.
2. Refrigeration System Start-Up
The compressor starts after the 15-second pressure
equalization, and remains on throughout the entire
Freeze and Harvest Sequences. The hot gas valve
remains on for 5 seconds during initial compressor start-
up and then shuts off.
At the same time the compressor starts, the condenser
fan motor (air-cooled models) is supplied with power
throughout the entire Freeze and Harvest Sequences.
The fan motor is wired through a fan cycle pressure
control, therefore it may cycle on and off. (The
compressor and condenser fan motor are wired through
the relay. As a result, any time the relay coil is energized,
the compressor and fan motor are supplied with power.)

FREEZE SEQUENCE

3. Prechill
The compressor is on for 30 seconds prior to water flow
to Prechill the evaporator.
4. Freeze
The water pump starts after the 30-second Prechill. An
even flow of water is directed across the evaporator and
into each cube cell, where it freezes.
When sufficient ice has formed, the water flow (not the
ice) contacts the ice thickness probe. After
approximately 7 seconds of continual water contact, the
Harvest Sequence is initiated. The ice machine cannot
initiate a Harvest Sequence until a 6-minute freeze time
has been surpassed.
Part Number 040001360 6/14
Section 3

Operation

HARVEST SEQUENCE

5. Harvest
The water pump de-energizes stopping flow over the
evaporator. The rising level of water in the sump trough
diverts water out of the overflow tube, purging excess
minerals from the sump trough. The hot gas valve also
opens to divert hot refrigerant gas into the evaporator.
The refrigerant gas warms the evaporator causing the
cubes to slide, as a sheet, off the evaporator and into the
storage bin. The sliding sheet of cubes contacts the ice
damper, opening the bin switch.
The momentary opening and re-closing of the bin switch
terminates the Harvest Sequence and returns the ice
machine to the Freeze Sequence (steps 3 - 4).
AUTOMATIC SHUT-OFF
6. Automatic Shut-Off
When the storage bin is full at the end of a Harvest
Sequence, the sheet of cubes fails to clear the ice
damper and will hold it down. After the ice damper is
held open for 7 seconds, the ice machine shuts off. The
ice machine remains off for 3 minutes before it can
automatically restart.
The ice machine remains off until enough ice has been
removed from the storage bin to allow the ice to fall clear
of the damper. As the ice damper swings back to the
operating position, the bin switch re-closes and the ice
machine restarts (steps 1 - 2), provided the 3-minute
delay period is complete.
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