Hoshizaki ice machine sequence of operation

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 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 and 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 (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 continues to run, PM and FMS energize, 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 continues to run, HGV opens, and FMS de-energizes.

PM stops for 2 seconds and reverses, 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. The pump-out

frequency control (S4 dip switch 5 & 6) is factory-adjusted to drain the water tank every

10th cycle thereafter, and no adjustment is required. However, where water quality is

bad and the icemaker needs a pump out more often, 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)."

7

How does Hoshizaki ice machine work?

What initiates the harvest cycle on Hoshizaki ice machine?

What is the harvest cycle on an ice machine?

How long does Hoshizaki Ice Maker take to make ice?