Manitowoc-ice Q Manuel d'utilisateur télécharger pdf (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.

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Manitowoc-ice Q Manuel d'utilisateur Page 34

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