Sequence Of Operation; One Minute Fill Cycle; Initial Harvest Cycle; Freeze Cycle - Hoshizaki KML-451MAH Service Manual

B. Sequence of Operation
The steps in the sequence are as outlined below. When power is supplied, a 5 second
delay occurs at startup. Note that the order of the LEDs from the outer edge of the board
is 1, 4, 3, 2.

1. One Minute Fill Cycle

LED 4 is on. WV opens and the fill period begins. After 1 minute, the board checks for
a closed F/S. If F/S is closed, the harvest cycle begins. If not, WV will remain energized
through additional 1 minute cycles until water enters the sump and F/S closes. This
serves as a low water safety to protect the water pump.

2. Initial Harvest Cycle

LEDs 1, 4, and 2 are on. WV remains open, Comp and FMR energize, HGV opens,
and harvest begins. As the evaporator warms, the thermistor located on the suction line
checks for a 48°F (9°C) temperature. When 48°F (9°C) is reached, a 3.9 kΩ signal turns
the harvest over to the adjustable harvest timer which is factory set for normal conditions.
The timer has settings of 60, 90, 120, and 180 seconds (dip switch 1 & 2). The water
valve is open during harvest for a maximum of 6 minutes or the length of harvest,
whichever is shorter. When the harvest timer completes its count down, the harvest cycle
is complete and the freeze cycle starts.The minimum total time allowed by the board for
a complete harvest cycle is 2 minutes.

3. Freeze Cycle

LED 1 is on. Comp and FMR continue to run, PM and FMS energize, LLV opens, HGV
and WV close and the freeze cycle starts. For the first 5 minutes the control board
will not accept a signal from F/S. This 5 minute minimum freeze acts as a short cycle
protection. At the end of 5 minutes, F/S assumes control. As ice builds on the evaporator
the water level in the sump lowers. The freeze continues until F/S opens and terminates
ice production.

4. Pump-Out Cycle

LEDs 1, 3, and 2 are on. Comp and FMR continue to run, HGV opens, LLV closes, and
FMS de-energizes. PM stops for 2 seconds. SR energizes, restarting PM and taking
water from the sump and forcing it to go through DV and down the drain. When the
pump-out timer stops counting, the pump out is complete.
Pump out always occurs on the 2nd harvest after startup. Then, depending on the control
board setting, pump out occurs every cycle, or every 2nd, 5th or 10th cycle (dip switch
5 & 6).

5. Normal Harvest Cycle

LEDs 1, 4, and 2 are on. Comp and FMR continue to run, HGV remains open and WV
opens. As the evaporator warms, the thermistor reaches 48°F (9°C). The control board
then receives the thermistor's 3.9 kΩ signal and starts the harvest timer. The water valve
is open during harvest for a maximum of 6 minutes or the length of harvest, whichever is
shorter. When the harvest timer completes its count down, the harvest cycle is complete
and the next freeze cycle starts. The unit continues to cycle through 3, 4 and 5 sequence
until the bin control senses ice and shuts the unit down.
Legend: Comp–compressor; DV–Drain Valve; FMR–remote fan motor; FMS–self-contained
fan motor; F/S–float switch; HGV–hot gas valve; LLV–Liquid Line Valve; PM–pump
motor; SR–Service Relay; WV–inlet water valve
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