S Model Operations
Ice Machine Operation
Sequence Of Operation
NOTE: The toggle switch must be in the ice position and the water curtain must be in place on the evaporator
before the ice machine will start. INITIAL START-UP OR START-UP AFTER AUTOMATIC SHUT-OFF
1. Water Purge
Before the compressor 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 valve(s) is also energized during water purge, although it stays on for an additional 5 seconds
(50 seconds total on time) during the initial refrigeration system start-up.
When Used - The air compressor energizes for the last 10 seconds of the cycle.
2. Refrigeration System Start-Up
The compressor starts after the 45 second water purge, and it remains on throughout the entire Freeze and
Harvest Sequences. The water fill valve is energized at the same time as the compressor. The harvest valve(s)
remains on for 5 seconds during initial compressor startup 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 contactor. As a result, anytime the contactor coil is energized, the compressor and fan motor are supplied
The compressor is on for 30 seconds (60 seconds initial cycle) prior to water flow, to prechill the evaporator. The
water fill valve remains on until the water level probe is satisfied.
The water pump restarts after the 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 and then off one more time to refill the water trough.
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.
NOTE: Freeze lock is bypassed after moving the toggle switch from OFF to ICE position for the first cycle only.
5. Water Purge
The harvest valve(s) opens at the beginning of the water purge to divert hot refrigerant gas into the evaporator.
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 (turns on) and de-energizes (turns off) strictly by time. The water fill
valve energizes for the last 15 seconds of the 45-second water purge.
After the 45 second water purge, the water fill valve, water pump and dump valve de-energize. (Refer to
“Water Purge Adjustment” for details.)
The harvest valve(s) remains open and 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 swings the water curtain out,
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 (Step 3 - 4.) When Used - The air compressor energizes after 35
seconds and remains energized throughout the entire harvest cycle. The air compressor will automatically
energize for 60 seconds when the harvest cycle time exceeded 75 seconds in the previous cycle.
7. Automatic Shut-Off
When the storage bin is full at the end of a harvest sequence, the sheet of cubes fails to clear the water
curtain and will hold it open. After the water curtain is held open for 30 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 water curtain. As the water curtain 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.
The control board has the following non-adjustable safety timers:
• The ice machine is locked into the freeze cycle for 6 minutes before a harvest cycle can be initiated.
Freeze lock is bypassed after moving the toggle switch from OFF to ICE position for the first cycle only.
• The maximum freeze time is 60 minutes at which time the control board automatically initiates a
harvest sequence (steps 5 & 6).
• The maximum harvest time is 3.5 minutes at which time the control board automatically initiates a freeze
sequence (steps 3 & 4).
WARM WATER RINSE CYCLE
Closing the back of the evaporator allows ice to build up on the rear of the evaporator and the plastic evaporator
frame parts. After 200 freeze/harvest cycles have been complete the control board will initiate a warm water rinse.
After the 200th harvest cycle ends:
• The Clean and Harvest LED’s energize to indicate the ice machine is in a warm water rinse.
• The compressor and harvest valve remain energized.
• The water pump energizes.
• The water inlet valve energizes until water contacts
the water level probe.
• The compressor and harvest valve warm the water for 5 minutes, then de-energize.
• The water pump remains energized for an additional 5 minutes (10 minute total on time) then deenergizes.
NOTE: The warm water rinse cycle can be terminated by moving the toggle switch to the OFF position, then back to ICE.
Manitowoc ice machines are factory-operated and adjusted before shipment. Normally, new installations do
not require any adjustment. To ensure proper operation, always follow the
• when starting the ice machine for the first time
• after a prolonged out of service period
• after cleaning and sanitizing
NOTE: Routine adjustments and maintenance procedures are not covered by the warranty.
The water level sensor is set to maintain the proper water level above the water pump housing. The water
level is not adjustable. If the water level is incorrect, check the water level probe for damage (probe bent,
etc.). Clean the water level probe with ice machine cleaner, rinse thoroughly and re-check operation. Repair
or replace the probe as necessary.
ICE THICKNESS CHECK
The ice thickness probe is factory-set to maintain the ice bridge thickness at 1/8" (.32 cm).
NOTE: Make sure the water curtain is in place when performing this check. It prevents water from splashing
out of the water trough.
1. Inspect the bridge connecting the cubes. It should be about 1/8" (.32 cm) thick.
2. If adjustment is necessary, turn the ice thickness probe adjustment screw clockwise to increase
bridge thickness, counterclockwise to decrease bridge thickness. Set at 1/4” gap between ice
machine and evaporator as starting point, then adjust to achieve a 1/8” 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
3. Make sure the ice thickness probe wire and the bracket do not restrict movement of the probe.
Water Level Probe Location
HARVEST SEQUENCE WATER PURGE
The harvest sequence water purge adjustment may be used when the ice machine is hooked up to special
water systems, such as a de-ionized water treatment system.
• The harvest sequence water purge is factory set for 45 seconds. Repositioning the jumper will set the
harvest water purge to 0 seconds. This setting does not affect the SeCs or AuCs (cleaning) sequences.
• During the harvest sequence water purge, the water fill valve energizes and de-energizes by time. The
water purge must be at the factory setting of 45 seconds for the water fill valve to energize during the
last 15 seconds of the water purge. If it is set to less than 45 seconds, the water fill valve will not energize
during the water purge.
Water Purge Adjustment
For your safety and to eliminate errors, we recommend that a qualified service technician make the harvest
water purge adjustment.
Disconnect electric power to the ice machine at the electrical disconnect before proceeding.
The harvest sequence water purge is factory-set at 45 seconds. A shorter purge setting (with standard
water supplies such as city water) is not recommended. This can increase water system cleaning and sanitizing requirements.