Foster F40 - Manual (Page 11)

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.
6.2 Defrost 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.
6.3 Operation - 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.
6.4 Components 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.
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E. At completion of the water filling phase (5 minutes) the unit passes automatically into the freezing cycle with the start up of:
COMPRESSOR
WATER PUMP
FAN MOTOR (in air cooled version) controlled by the condensing temperature sensor located within the condenser fins (Fig.2). Page 20.
10.2 Operational Checks
F. Install, if necessary, the refrigerant service gauges on both the high side and low side Schräder valves to check the compressor head and
suction pressures.
NOTE: On air cooled models, the condenser temperature sensor, which is located within the condenser fins, keep the head (condensing)
pressure between 13,5 and 14,5 bars (190-205 psig).
In the water cooled models the discharge pressure is kept constant at the value of 14 bars (195 psig) by means of the water regulating valve
located in the water supply line to the condenser.
In case of condenser clogging such to prevent the proper flow of the cooling air or fan motor out of operation, the condenser temperature rises
and when it reaches 70°C (160°F) the condenser temperature sensor shuts-off the ice maker with the consequent light-up of the RED WARNING
LIGHT (Fig.3). Page 20.
The same happen even for the water cooled version where the condenser probe is placed in contact with the refrigerant liquid line.
When its temperature reaches 62°C (145°F) it trips-off automatically the machine.
After having diagnosed the reason of the rise in temperature and removed its cause, it is necessary to turn the head of the selector - always
using an appropriate screwdriver - first on the RE-SET position then return it on previous OPERATION position, thus to put the machine in
condition to initiate a new freezing cycle.
The same can also be done by just switching OFF and ON the unit at main line switch.
In both cases the machine restarts with the usual 5 minutes water filling phase in order to provide enough water into the sump tank.
G. Check to see through the ice discharge opening that the spray systems are correctly seated and that the water jets uniformly reach the interior
of the inverted mould cups; also make sure that the plastic curtain is hanging freely and there is no excessive water spillage through it.
H. The ice making process takes place thereby, with water sprayed into the moulds that gets gradually refrigerated by the heat exchange with the
refrigerant flowing into the evaporator serpentine.
During the freezing process, when the evaporator temperature falls below an established value, the evaporator temperature sensor supplies a
low voltage power signal to the electronic control device (P.C. BOARD) in order to activate an electronic timer. This one takes over the control
of the freezing cycle up to the complete formation of the ice cubes (Fig.4) Page 20.
NOTE: The length of the entire freezing cycle if govened by the evaporator temperature sensor which has its probe placed in contact with
the evaporator serpentine (Non adjustable) in combination with the electronic timer (Adjustable) incorporated in the P.C. BOARD. The timer
adjustment is factory set in consideration of cooling version and ice cube size (Medium, Large).
It is possible, however, to modify the timed length of the freezing cycle, by changing the DIP SWITCH keys setting.
In Table B, Page 18 are shown the various time extensions of the freezing cycle second phase, in relation with the different DIP SWITCH
settings.
I. After about 15-18 minutes from the beginning of the freezing cycle, in an hypothetic ambient temperature of 21°C, the defrost cycle takes place
with the hot gas and the water inlet valves being simultaneously activated (Fig.5). Page 20. The electrical components in operation are:
COMPRESSOR
WATER INLET SOLENOID VALVE
HOT GAS VALVE
and, if installed
WATER DRAIN SOLENOID VALVE
NOTE: The length of the defrost cycle is determined by the DIP SWITCH keys setting in conjunction with the ambient temperature sensor
located just in front of the condenser. The length of defrost cycle can be adjusted by changing the combination setting of keys 5, 6 and 7 of
DIP SWITCH as illustrated on Table C. Page 18.
As shown, per each individual key combination, it is possible to have a different length of the defrost cycle in relation to the different ambient
temperature situations; shorter when the ambient temperature is high and longer in colder ambient’s to partially compensate for the length of
the freezing cycle, which is longer in high ambient temperatures and shorter in low ones.
J. Check, during the defrost cycle, that the incoming water flows correctly into the sump reservoir in order to refill it and that the surplus overflows
through the overflow drain tube.
K. Check the texture of ice cubes just released. They have to be in the right shape with a small depression of about 5-6mm in their crown.
If not, wait for the completion of the second cycle before performing any adjustment.
If required, the length of the timed freezing cycle can be modified by changing the DIP SWITCH keys setting as illustrated in Table B Page
18.
If the ice cubes are shallow and cloudy, it is possible that the ice maker runs short of water during the freezing cycle second phase or, the quality
of the supplied water requires the use of an appropriate water filter or conditioner.
L. To be sure of the correct operation of ice level control device, place one hand between its sensing “eyes” to interrupt the light beam.
The RED LIGHT located in the front of the P.C. BOARD goes immediately OFF, and after 60 seconds, the unit stops with the simultaneous
glowing of the 2nd YELLOW LIGHT to monitor the BIN FULL situation (Fig.6) Page 20.
Take the hand out from the ice level control sensors to allow the resumption of the light beam; the RED LIGHT, located in the front of the P.C.
BOARD, will glow immediately.
After approximately 6 seconds the ice maker resumes its operation with the immediate glowing of the FOURTH YELLOW LIGHT indicating
UNIT IN OPERATION and the extinguishing of the “BIN FULL” YELLOW LIGHT.
NOTE: The ICE LEVEL CONTROL (INFRARED SYSTEM) is independent from the temperature however, the reliability of its detection can be
affected by external light radiation’s or by any sort of dirt and scale sediment which may deposit directly on the light source and on the receiver.
To prevent any possible ice maker malfunction, due to negative affection of the light detector, it is advisable to locate the unit where it is not
reached by any direct light beam or light radiation, also it is recommended to keep the bin door constantly closed and to follow the instructions
for the periodical cleaning of the light sensor elements as detailed in the MAINTENANCE AND CLEANING PROCEDURES.
M. Remove, in installed, the refrigerant service gauges and re-fit the unit service panels previously removed.
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