Hoshizaki KM-151BAH - Manual (Page 12)

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2. 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 5, 6, 8, 4, 7.
[a] ONE MINUTE FILL CYCLE
LED 8 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.
[b] INITIAL HARVEST CYCLE
LEDs 5, 6, and 8 are on. WV remains open, Comp energizes, 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 (S1 dip switch 1 & 2). 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. WV is open during harvest for a maximum of 6 minutes or the length of
harvest minus 0, 10, 30, or 50 seconds (adjustable by S1 dip switch 7 & 8), whichever is
shorter. LED 8 goes off when WV closes. PM energizes and runs for the last 0, 10, 30,
or 50 seconds of harvest depending on S1 dip switch 7 & 8 setting. LED 7 comes on
when PM energizes. At the end of harvest, the control board checks the position of F/S
and proceeds to the freeze cycle if it is closed or calls for a 1-minute fill if it is open.
[c] FREEZE CYCLE
LEDs 5 & 7 are on. Comp continues to run, PM and FMS energize, HGV closes and
the freeze cycle starts. For the first 5 minutes after the thermistor temperature reaches
36°F (2°C), the control board will not accept a signal from F/S. This minimum freeze
period acts as a short cycle protection. At the end of this period, F/S assumes control.
As the evaporator cools, the thermistor located on the suction line checks for a 34°F (1°C)
temperature. When 34°F (1°C) is reached, a 5.8 kΩ signal causes the control board to
de-energize the pump motor for 10 seconds. This is to prevent slushing. As ice builds
on the evaporator the water level in the sump lowers. The freeze continues until F/S
opens and terminates ice production.