7
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 k
Ω
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)."
