7. The DIP. SWITCH keys setting is made in consideration of the model and of the type of condenser used (air or water cooled).
In Table B, page 12, are indicated the various lengths of the third portion of freezing cycle (Time mode) in accordance with the different combinations of the DIP. SWITCH KEYS.
In Table A, page 12, are indicated the DIP. SWITCH keys combinations for the different models and versions as they are set in the factory. The electrical components in operation during the freezing cycle are:
COMPRESSOR
FAN MOTOR (in air cooled version)
WATER PUMP and during the timed phase of freezing cycle (Time mode) they are joined by the ELECTRONIC TIMER.
On the air cooled versions the refrigerant head pressure is gradually reduced from a value of approx. 15 bars (210psig), generally recorded at the beginning of the freezing cycle with the unit at 21˚C (70˚F) ambient temperature, to a minimum value of approx. 11 bars (155psig) just at the end of the freezing cycle a few seconds before the starting of the defrost cycle.
The above values are in relation as well to the ambient temperature of the ice maker site and are subject to rise with the increase of this temperature.
On the water cooled versions the refrigerant head pressure ranges between 13.5 and 14.5 bars (190-205psig)being controlled by the automatic high pressure control that energises a water solenoid valve located on the inlet water line to the condenser, which modulates the cooling water rate to the condenser.
With the unit installed in standard location (21˚C ambient temperature) at the start of the freezing cycle the refrigerant suction or low-pressure lowers rapidly to 3.5 bars (50psig) then declines gradually, in relation with the growing of the ice thickness, to reach, at the end of the cycle approx. 1.0 to 1.3 bars (14-l8psig)on 20,30 and 65 and at approx. 0.6 bars (8.5psig) on 40 with the cubes fully formed in the cup moulds.
6.2Defrost or Harvest Cycle
As the electronic timer has carried the system throughout the third phase of freezing cycle or as soon as the second phase T2 is over (when its length has been as long as 35 to 45 minutes) the defrost cycle starts.
NOTE: The length of the defrost cycle (non-adjustable) is related to the length of the second phase of freezing cycle T2 as detailed in Table C. Page 12.
The electrical components in operation during this phase are:
COMPRESSOR
WATER INLET SOLENOID VALVE
HOT GAS SOLENOID VALVE
The incoming water, passing through the water inlet valve and its flow control, runs over the evaporator platen and then flows by gravity through the dribbler holes down into the sump / reservoir.
The overflow, located in the sump tank, limits the level of the water which will be used to produce the next batch of ice cubes.
Meanwhile, the refrigerant as hot gas, discharged from the compressor, flows through the hot gas valve directly into the evaporator serpentine bypassing the condenser.
The hot gas circulating in the serpentine of the evaporator warms up the copper moulds causing the ice cubes to defrost. The ice cubes, released from the cups, drop by gravity onto a slanted cube chute, then through a curtained opening fall into the storage bin.
At the end of the defrost cycle, both the hot gas and the water inlet valves close and the machine starts again a new freezing cycle.
6.3Operation - Control Sequence
At the start of freezing cycle the evaporator temperature sensor controls the length of the first T1 and second T2 portion of the freezing cycle. As it senses the predetermined evaporating temperature of -13˚C (8.5˚F) (-16˚C on 85) it supplies a low voltage current to the P.C. BOARD in order to activate the electronic timer which takes over the control of the remaining portion of the freezing cycle for a pre-fixed time Ta subject to the DIP SWITCH keys setting (see Table B). Page 12.
NOTE: The evaporator temperature sensor, factory pre-set, is the same for all models and is not adjustable in the field.
During the normal operation mode the length or the total time of the freezing cycle is equal to the sum of the three partial times i.e.:
Tc = T1 + T2 + Ta
In case the length of the second portion of the freezing cycle or time T2 gets long as to be between 35 and 45 minutes, the total length of the freezing cycle will be limited to:
Tc = T1 + T2
skipping the added time Ta, controlled by the electronic timer.
If instead the time T2 gets longer than 45 minutes the unit stops immediately with the lighting up of the warning RED LIGHT. The same could happen in case the time T1 (1st portion of freezing cycle) gets longer than 15 minutes.
Once completed the freezing cycle 2nd or 3rd phase (this last one is dependent on the length of the second phase of freezing cycle - T2) the system goes automatically into the defrost cycle Ts.
The defrost cycle also has a prefixed length that can vary in relation to the time T2, as shown in Table C.
At completion of the defrost cycle the P.C. BOARD puts the unit into a new freezing cycle.
6.4Components Description
A.EVAPORATOR TEMPERATURE SENSOR
The evaporator temperature sensor probe, located in contact with the evaporator serpentine, detects the dropping of the evaporator temperature during the freezing cycle and signals it by supplying a current flow to the microprocessor of The P.C. BOARD.
According to the current signal and to how long after this is received, the microprocessor may or not give the consent to the ice maker to complete the freezing cycle.
The low voltage current transmitted, from the evaporator temperature sensor to the P.C. BOARD, is signalled by the lighting up of the fourth (Time T2) and fifth (Time T1) RED LEDS placed in the front of the P.C. BOARD to inform the service engineer, of the normal (regular) progression of the freezing cycle.
