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Manitowoc Undercounter Operations

Ice Machine Operation

Ice Making Sequence of Operation
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.)
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.
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).
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
Your Manitowoc ice machine was factory-operated and adjusted before shipment. Normally, a newly installed ice machine does not require any adjustment.
To ensure proper operation, always follow these Operational Checks when starting the ice machine:
• for the first time
• after a prolonged out of service period
• after cleaning and sanitizing
Routine adjustments and maintenance procedures outlined in this manual are not covered by the warranty.
To reduce mineral build-up and cleaning frequency, the water in the sump trough must be purged during each harvest cycle.
When the water pump de-energizes the level in the water trough rises above the standpipe starting a siphon action.
The siphon action stops when the water level in the sump trough drops. When the siphon action stops, the float valve
refills the water trough to the correct level.
Siphon System Check
Follow steps 1 through 6 under water level check.
Before water will flow into the water trough the float valve shut-off must be in the OPEN position. DRAIN STANDPIPE
Check the water level while the ice machine is in the ice mode and the water pump is running. The correct water level is 1/4" (6.3mm) to 3/8″ (9.5mm) below the top of the standpipe a line in the water trough indicates the correct level.
Water Level
The float valve is factory-set for the proper water level. If adjustments are necessary:
1. Verify the ice machine is level (see page 2-4).
2. Remove the siphon cap from the standpipe.
3. Place the main ON/OFF/WASH toggle switch to the ON position, and wait until the float valve stops adding water.
4. Adjust the water level to (1/4" to 3/8"
(6.3 to 9.5 mm) below the standpipe) the line in the water trough:
A Loosen the two screws on the float valve bracket.
B Raise or lower the float valve assembly as necessary, then tighten the screws.
5. Move the main ON/OFF/ WASH toggle switch to the OFF position. The water level in the trough will rise above the standpipe and run down the drain.
6. Replace the siphon cap on the standpipe, and verify water level and siphon action by repeating steps 3 through 5.
The ice thickness probe is factory-set to maintain the ice bridge thickness at 1/8” (3.2 mm).
1. Inspect the bridge connecting the cubes. It should be about 1/8” (3.2 mm) thick.
2. If adjustment is necessary, turn the ice thickness probe adjustment screw clockwise to increase bridge thickness, or counterclockwise to decrease bridge thickness.
NOTE: Turning the adjustment 1/3 of a turn will change the ice thickness about 1/16” (1.5 mm).

Ice Thickness Check
Make sure the ice thickness probe wire and the bracket do not restrict movement of the probe.