II
°
PORTION HARVEST CYCLE
Electrical components (Loads) ....... ON
OFF
Compressor ........................................
•
Fan motor (SDN25
÷
45 ON) ...............
•
Hot gas valve .....................................
•
Water inlet valve .................................
•
Water pump ........................................
•
Contactor coil .....................................
•
Timer motor ........................................
•
Electric Controls .............................. ON
OFF
Conctats 3-4 evaporator thermostat ..
•
Conctats 3-2 evaporator thermostat ..
•
Bin thermostat ....................................
•
Conctats COM-NO timer microswitch
•
Conctats COM-NC timer microswitch
•
Pressure control (SDN25
÷
65W) (SDN65
÷
SD210A)
•
OPERATING CHARACTERISTICS
On air cooled models during the freezing cycle
the discharge pressure is kept between 8
÷
10
bars (110
÷
140 psig) SDN25
÷
SD80, 15,5
÷
20 bars
(215
÷
280 psig) SD 125-210.
At the same time the suction pressure will
gradually decline, reaching its lowest point just
before harvest. Compressor amps experience a
similar drop.
COMPONENTS DESCRIPTION
A.
MASTER SWITCH
Fitted on the front side of the unit cabinet the
master switch has to be used to start-up and to
stop the ice maker operation.
In connection with it there is the green monitor
light.
B.
EVAPORATOR THERMOSTAT
The evaporator thermostat with its sensing bulb
intimately in contact with the refrigerant outlet
tube from the evaporator, senses the evaporating
refrigerant temperature (which declines in the
course of the freezing cycle) and when this one
reaches the pre-set value, it switches its contacts
from 3-4 to 3-2 to activate the finishing cycle (2nd
phase) which has a pre-set extension determined
by the large diameter lobe of the timer cam.
C.
BIN THERMOSTAT
The bin thermostat, which has its sensing bulb
downward into the storage bin, shuts-OFF
automatically the icemaker when the ice storage
bin is filled and ice contacts its bulb. Being it
connected in series with the front microswitch of
the timer, it causes the unit shut-off only at the
end of the freezing cycle, when the ice cubes are
completed.
After ice is removed from the bin and its bulb
warm-up it allows the unit to restart from the
beginning of the harvest cycle which, in the
circumstance, is more likely a water filling cycle.
D.
TIMER
Equipped with two microswitches which plungers
ride one timer cam, the timer is located inside the
control box.
The function of the timer begins when activated
by the cube size control (evap. thermostat).
The large diameter lobe of its cam determines
the 2nd freezing cycle portion length, while the
cam small diameter lobe, determines the time
cycle for the harvest sequence.
The timer cam can be adjusted to vary the defrost
time as required.
WARNING. Never set the defrost time for
longer than 4 minutes as this will
jeopardize the compressor motor
windings.
It goes without saying that an extension of the
defrost period will directly reduce the timed portion
of the freezing cycle and viceversa.
Consequently any variation made at the timer
cam setting requires a compensation adjustment,
very fine and very accurate, of the evaporator
thermostat.
E.
COMPRESSOR SWITCH
The compressor switch is located on the edge of
the control box and it can be switched in two
different positions which are:
Operation
Supply power directly to the
compressor motor or, on models
SD 80, SD 125 and SD 210, directly
to the contactor coil.
Cleaning
Shuts-off the compressor so that
only the water pump and the water
inlet valve will remain in operation.
When positioned on “0 - OFF” the water pump
primes the cleaning or the bactericide solution
allover the unit water system to generate a good
cleaning and sanitizing action of the ice maker.
NOTE. It is recommended to avoid the rinsing,
after the sanitation of the unit water system,
as any bactericide coating, which is beneficial
to limit the bacteria growth, left-over in the
system may be removed.
F.
HI PRESSURE CONTROL
Used either on air (SDN65-SD80-125-210A) and
water (SDN25
÷
65W) cooled ice makers it
functions to maintain the head pressure within
the preset values of 8
÷
10 bars (110
÷
140 psig)
SDN25
÷
SD80, and 15,5
÷
20 bars (215
÷
280 psig)
SD 125-210, by intermittently activating the fan
motor (in the air cooled models) and the water
inlet valve to the condenser (in the water cooled
models SDN25-30-35-45-65).
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