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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 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 k
Ω
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 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 and FMR continue to run, PM and FMS energize, LLV opens, 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 and FMR continue to run, HGV opens, LLV closes, 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 pump-out frequency control (S4 dip switch
5 & 6) is factory-adjusted to drain the water tank every cycle, and no adjustment should
be made.
