Hoshizaki KM-901MWH - Manual (Page 20)

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B. Sequence of Operation
1. Sequence Cycles and Shutdown
a) "E" Control Board: Auxiliary Code T-0, U-0
The steps in the sequence are as outlined below. When power is supplied, CB red
"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 1, 4, 3, 2.
(1) 1-Minute Fill Cycle
LED 4 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.
(2) Initial Harvest Cycle
LEDs 1, 4, and 2 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 (S4 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 (S4 dip switch 1 & 2)." WV is energized during
harvest for a maximum of 6 minutes or the length of harvest, whichever is shorter.
LED 4 goes off when WV de-energizes. When the harvest timer expires, the harvest
cycle is complete. CB checks the position of F/S and proceeds to the next 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.
(3) Freeze Cycle
LED 1 is on. Comp and FMR remain energized, PM, FM, and LLV energize, HGV
and WV de-energize. For the first 5 minutes, CB will not accept a signal from F/S.
This minimum 5-minute freeze time is short cycle protection for Comp. At the end of
5 minutes, 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.
(4) Pump-Out Cycle
LEDs 1, 3, and 2 are on. LED 4 is on when S4 dip switch 3 & 4 are set to 3 off and
4 on. Comp and FMR remain energized. HGV energizes. WV energizes if S4 dip
switch 3 off and 4 on. LLV and FM de-energize. PM stops for 2 seconds then
reverses, taking water from the bottom of the tank 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 F/S. When the
pump-out timer expires, the pump-out is complete.
The first pump-out occurs after the 1st freeze cycle, then every 10th cycle thereafter.
The pump-out frequency is factory set, and generally 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. For details, see "II.C.3.d) Pump-Out Frequency Control (S4 dip
switch 5 & 6)."