Hoshizaki KM-901MRH/3, KM-901MWH, KM-901MAH Sequence of Operation, Sequence Cycles and Shutdown

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)."

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