Sequence Of Operation; Sequence Cycles And Shutdown; A) 1-Minute Fill Cycle; B) Initial Harvest Cycle - Hoshizaki KMD-450MAH Service Manual

B. Sequence of Operation

1. Sequence Cycles and Shutdown

The steps in the sequence are as outlined below. When power is supplied, CB "POWER
OK" LED comes on. There is a 5-second delay before startup. Note that the order of the
component LEDs from the outer edge of CB is 5, 6, 8, 9, 4, 7.

a) 1-Minute Fill Cycle

LED 8 is on. WV energizes and the 1-minute fill cycle begins. After 1 minute, CB checks
for a closed F/S. If F/S is closed, the harvest cycle begins. If not, WV remains energized
through additional 1-minute fill cycles until water fills the tank and closes F/S. This
serves as a low water safety to protect PM.

b) Initial Harvest Cycle

LEDs 5, 6, and 8 are on. WV remains energized, Comp, FMR, HGV energize.
CB monitors the warming of the evaporator via the thermistor located on the suction line.
When the thermistor reaches 48°F (9°C), CB reads a 3.9 kΩ signal from the thermistor
and turns harvest termination over to the harvest timer (S1 dip switch 1 & 2). The
harvest timer has settings of 60, 90, 120, and 180 seconds. For details, see "II.C.3.b)
Harvest Timer (S1 dip switch 1 & 2)." WV is energized during harvest for a maximum of
6 minutes or the length of harvest minus 0, 10, 30, or 50 seconds (harvest pump timer
(S1 dip switch 7 & 8)), whichever is shorter. For details, see "II.C.3.e) Harvest Pump
Timer (S1 dip switch 7 & 8)." LED 8 goes off when WV de-energizes. LED 7 comes on
and PM energizes and runs for the last 0, 10, 30, or 50 seconds of harvest depending
on the harvest pump timer setting. This circulates water over the evaporator for the last
0, 10, 30, or 50 seconds of harvest. When the harvest timer expires, the harvest cycle is
complete. CB checks the position of F/S and proceeds to the freeze cycle if it is closed
or calls for a 1-minute fill cycle if it is open. The minimum total time allowed by CB for a
complete harvest cycle is 2 minutes.

c) Freeze Cycle

LEDs 5 & 7 are on. Comp and FMR remain energized, PM energizes or remains
energized depending on the harvest pump timer (S1 dip switch 7 & 8) setting. FM and
LLV energize, HGV and WV (may de-energize during harvest cycle) de-energize. CB
monitors the cooling of the evaporator via the thermistor located on the suction line.
When the thermistor drops to 36°F (2°C), CB reads a 5.5 kΩ signal from the thermistor
and starts a 5-minute short cycle protection timer. CB will not accept a signal from F/S
until the 5-minute timer expires. After the 5-minute timer expires, F/S assumes control.
As ice builds on the evaporator, the water level in the tank lowers. The freeze cycle
continues until F/S opens and terminates the cycle.
The float switch selector (S2 dip switch 2) and the refill counter (S2 dip switch 3 & 4)
allow certain models to use a double F/S to refill the water tank during the freeze cycle.
The KMD-450MAH and KMD-450MWH use a single F/S and do not refill. For details,
see "II.C.3.h) Float Switch Selector (S2 dip switch 2)" and "II.C.3.i) Refill Counter (S2 dip
switch 3 & 4)." CAUTION! Do not adjust S2 dip switch 2, 3, or 4 out of the factory
default position on this model. These dip switches must be left in the factory
default position or this unit will not operate correctly.
The anti-slush control (S2 dip switch 6) helps prevent slushing during the freeze cycle
on certain models. When activated, the control board monitors the cooling of the
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