Hoshizaki KM-501MWH User Manual download pdf (Page 13)

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 deenergizes. PM stops for 2 seconds and reverses, taking water from the bottom of

the sump and forcing pressure against the check valve seat allowing water to go through

the check valve and down the drain. At the same time water ﬂows through the small tube

to power ﬂush the F/S. 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; FMR–remote fan motor; FMS–self-contained fan motor;

F/S–ﬂoat switch; HGV–hot gas valve; LLV–Liquid Line Valve; PM–pump motor;

WV–inlet water valve

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Hoshizaki KM-501MWH User Manual Page 13

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