Sequence Of Operation; One Minute Fill Cycle; Initial Harvest Cycle; Freeze Cycle - Hoshizaki KM-1900SAH Service Manual

B. Sequence of Operation
The steps in the sequence are as outlined below. When power is supplied, the red
"POWER OK" LED on the control board comes on. 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 control 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 PM.

2. Initial Harvest Cycle

LEDs 1, 4, and 2 are on. WV remains open, Comp, FMR, and HGV opens. 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
(S4 dip switch 1 & 2) which is factory set for normal conditions. The harvest timer has
settings of 60, 90, 120, and 180 seconds. For details, see "II.C.3.b) Harvest Timer (S4
dip switch 1 & 2)." When the harvest timer completes its countdown, the harvest cycle
is complete and the freeze cycle starts. The minimum total time allowed by the control
board for a complete harvest cycle is 2 minutes. WV is energized during harvest for
a maximum of 6 minutes or the length of harvest, whichever is shorter. 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 and FMR continue to run, PM and FMS energize, and 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. The pump motor then re-starts in the
reverse direction, 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 (S4 dip switch 3 & 4) stops counting, the pump out is complete. The
1st pump out occurs after the 1st freeze cycle and every 10th cycle thereafter. The
pump-out frequency control (S4 dip switch 5 & 6) 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 (S4 dip switch 5 & 6) can be set to have
a pump out occur every cycle, or every 2, 5, or 10 cycles, see "II.C.3.d) Pump-Out
Frequency Control (S4 dip switch 5 & 6)."
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