Sequence Of Operation; One Minute Fill Cycle; Initial Harvest Cycle; Freeze Cycle - Hoshizaki KMD-850MAH Service Manual

B. Sequence of Operation
The steps in the sequence are as outlined below. When power is supplied, the red
"POWER OK" LED and the green "BC CLOSED" LED on the control board come on (If
the yellow "BC OPEN" LED is on, the unit will not start. In this case clear ice away from
the bin control actuator). A 5-second delay occurs at startup. Note that the order of the
green sequence 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, FMR, HGV energize. The control
board monitors the warming of the evaporator via the thermistor located on the suction
line. When the thermistor reaches 48°F (9°C), the control board reads a 3.9 kΩ signal
from the thermistor and turns harvest termination over to the adjustable harvest timer
which is factory set for normal conditions. The timer has settings of 60, 90, 120, and
180 seconds (S4 dip switch 1 & 2). For details, see "II.C.3.b) Harvest Timer." When the
harvest timer completes its countdown, 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 50 seconds, whichever is shorter. LED 4 goes off when WV closes.
PM energizes and runs for the last 50 seconds of harvest. LED 3 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.

3. Freeze Cycle

LED 1 is on. Comp, FMR, and PM continue to run, FMS energizes, LLV opens, HGV
closes 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, 4, 3, and 2 are on. With S4 dip switch 5 and 6 in the factory default position, the
1st pump out occurs after the 11th freeze cycle and every 10th cycle thereafter. Comp
and FMR continue to run, DV and WV open, 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. At the same time, water
flows through the vent tube to power flush the F/S. After 10 seconds, the pump out is
complete. The pump-out frequency control is factory-adjusted to drain the water tank
every 10 cycles, and no adjustment is required. However, where water quality is bad and
the icemaker needs a pump out more often, the pump-out frequency can be adjusted.
The pump-out frequency control can be set to have a pump out occur every cycle,
or every 2, 5, or 10 cycles (S4 dip switch 5 & 6). For details, see "II.C.3.d) Pump-Out
Frequency Control."
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