5
2. SEQUENCE OF OPERATION
The steps in the sequence are as outlined below. When power is supplied, a 5 second
delay occurs at startup. Note that the order of the LEDs from the outer edge of the board
is 5, 6, 8, 4, 7.
[a] ONE MINUTE FILL CYCLE
LED 8 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.
[b] INITIAL HARVEST CYCLE
LEDs 5, 6, and 8 are on. WV remains open, Comp energizes, HGV opens, and harvest
begins. As the evaporator warms, the thermistor located on the suction line checks
for a 9°C temperature. When 9°C is reached, a 3.9 kΩ signal turns the harvest over to
the adjustable harvest timer which is factory set for normal conditions. The timer has
settings of 60, 90, 120, and 180 seconds (S1 dip switch 1 & 2). When the harvest timer
completes its count down, 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 0, 10,
30, or 50 seconds (adjustable by S1 dip switch 7 & 8), whichever is shorter. LED 8 goes
off when WV closes. PM energizes and runs for the last 0, 10, 30, or 50 seconds of
harvest depending on S1 dip switch 7 & 8 setting. LED 7 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.
[c] FREEZE CYCLE
LEDs 5 & 7 are on. Comp continues to run, PM and FMS energize, HGV closes and the
freeze cycle starts. For the first 5 minutes after the thermistor temperature reaches 2°C,
the control board will not accept a signal from F/S. This minimum freeze period acts as a
short cycle protection. At the end of this period, F/S assumes control. As the evaporator
cools, the thermistor located on the suction line checks the temperature and PM stops
(see “III. 3. TIMING CHART” for details). This is to prevent slushing. As ice builds on the
evaporator the water level in the sump lowers. The freeze continues until F/S opens and
terminates ice production.
