Manitowoc Ice Q - Manual (Page 34)

Ice Machine Operation Section 3
3-2 Part Number 000001530
Ice Making Sequence of Operation
INITIAL START-UP OR START-UP AFTER
AUTOMATIC SHUT-OFF
1. Water Purge
Before the refrigeration system starts, the water pump
and water dump solenoid are energized for 45 seconds,
to completely purge the ice machine of old water. This
feature ensures that the ice making cycle starts with
fresh water. The harvest solenoid valves are also
energized during the water purge, although they stay on
for an additional 5 seconds (50 seconds total on time)
then shuts off.
2. Refrigeration System Start-Up
Ice Machine Head Section: The liquid line solenoid
valve energizes after the 45 second water purge and
remains on throughout the entire Freeze and Harvest
Sequences. The harvest solenoid valves remains on for
5 seconds during initial compressor start-up and then
shuts off.
The water fill valve is energized at the same time as the
liquid line solenoid valve.
CVD Condensing Unit: When the refrigerant pressure
is high enough to close the low pressure control, (after
the cool vapor valves energize in step 1) the contactor
coil is energized and the compressor starts. The
compressor and fan cycling control are supplied with
power throughout the entire Freeze and Harvest
Sequences. When the refrigerant pressure is high
enough to close the fan cycling pressure control the
condenser fan motor starts.
FREEZE SEQUENCE
3. Prechill
The liquid line solenoid is energized for 30 seconds prior
to water flow. This allows the refrigeration system to start
up and prechill the evaporator. The water fill valve
remains energized until the water level sensor is
satisfied.
4. Freeze
The water pump restarts after the 30 second Prechill. An
even flow of water is directed across the evaporator and
into each cube cell, where it freezes. The water fill valve
will cycle on one more time to refill the water trough as
needed.
When sufficient ice has formed, the water flow (not the
ice) contacts the ice thickness probe. After
approximately 10 seconds of continual water contact,
the Harvest Sequence is initiated. The ice machine
cannot initiate a Harvest Sequence until a 6-minute
freeze lock has been surpassed.
HARVEST SEQUENCE
5. Water Purge
The water pump continues to run, and the water dump
valve energizes for 45 seconds to purge the water in the
sump trough. The water fill valve energizes for the last
15 seconds of the 45 second water purge. After the
45 second water purge, the water pump and dump
solenoid valve de-energize. The harvest solenoids open
at the beginning of water purge.
6. Harvest
The harvest solenoid valves remain open and the
refrigerant warms each evaporator causing the cubes to
slide as a sheet, off the evaporator and into the storage
bin. The ice may fall first from either the right or the left
evaporator, or both at the same time. The sliding sheet
of cubes swings the water curtain out, opening the
corresponding bin switch, which causes relay #5 or #6 to
open. Opening relay #5 or #6 de-energizes the
corresponding harvest solenoid valve for the remainder
of the Harvest Sequence. The momentary opening and
re-closing of both bin switches terminates the Harvest
Sequence and returns the ice machine to the Freeze
Sequence (steps 3-4).
6a. Water Assist Harvest Feature
Typical duration of a harvest sequence is less than 2.5
minutes when the harvest sequence time reaches 4
minutes the following occurs:
4 minutes into a Harvest Sequence. The water fill valve
will energize to fill the trough with water.
5 minutes into a Harvest Sequence. The water pump will
energize and flow water over the evaporators.
The water fill valve and water pump remain on until all
bin switches have been activated, or until the 7 minute
Harvest Sequence time limit is reached.