B. Sequence of Operation. Hoshizaki KMD-850MAH, KMD-850MWH, KMD-850MRH

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 deenergizes. 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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5. Normal Harvest Cycle

LEDs 1, 4, and 2 are on. Comp, FMR, and HGV remain energized and WV opens. PM stops. As the evaporator warms, the thermistor reaches 48°F (9°C). The control board then receives the thermistor's 3.9 kΩ signal and starts the harvest timer. When the harvest timer completes its countdown, the harvest cycle is complete. The minimum total time allowed by the 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 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.

The unit continues to cycle through freeze and harvest cycles until the bin control activates (opens) and shuts the unit down.

Note: To prevent incomplete batches of ice from forming on the evaporator, the control board will only shut down the machine within the first 5 minutes of the freeze cycle. If ice pushes the bin control actuator in (open) after the first five minutes of the freeze cycle, the control board will allow the machine to complete the freeze cycle and the following harvest cycle before shutting down the machine.

Legend: Comp–compressor; DV–Drain Valve; FMR–remote fan motor; FMS–self-contained

fan motor; F/S–float switch; HGV–hot gas valve; LLV–liquid line valve;

PM–pump motor; SR–service relay; WV–inlet water valve

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