Principle Of Operation (How It Works); Water Circuit; Refrigerant Circuit - Scotsman AF 80 Service Manual

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WATER CIRCUIT

The water enter in the machine through the water
inlet fitting which incorporates a strainer and it is
located at the rear side of the cabinet and then it
goes to the water reservoir flowing through a float
valve.
NOTE. The presence of the water in the float
reservoir is detected by a system of two
sensors which operates in conjunction with
the P.C. Board. The two sensors use the
water as a conductor to maintain a low voltage
current flow between them signalling in this
way to the P.C. Board the presence of the
water in the reservoir. In case the water used
is very soft (de-mineralized) or the float
reservoir gets empty the current flow between
the sensors become so weak or is no longer
maintained that, as consequence, the P.C.
Board shutoff the flaker operation with the
simultaneous glowing of the YELLOW LED
signalling "Shortage of water".
The float reservoir is positioned at the side of the
freezing cylinder at such an height to be able to
maintain a constant water level around the freezer
auger.
In fact, the water flows from the reservoir into the
bottom inlet of the freezing cylinder to sorround
the stainless steel auger which is vertically fitted
in the center of the freezer.
In the freezer the incoming water gets chilled into
soft (slush) ice which is moved upward by the
rotating action of the auger. The stainless steel
auger that rotates counter-clockwise within the
freezer, is powered by a direct drive gear motor
and carries the ice upward along the refrigerated
freezer inner walls and by doing so the ice gets
progressively thicker and harder.
FLOAT TANK
FLOAT VALVE
FREEZER
FREEZER WATER
FEED LINE
The ice, being costantly lifted up, meet the toothed
point of the ice breaker which is fitted on the top
end of the auger, where it gets compacted,
cracked and forced to change from vertical into
PRINCIPLE OF OPERATION
horizontal motion to be discharged out, through
the ice spout, into the storage bin.
By running the ice maker, i.e. by putting the unit
under power, starts the automatic and continuous
icemaking process which would not stop until the
ice storage bin gets filled-up to the level of the
control "eyes" located on the sides of the ice
spout.
As the ice level raises to interrupt the light beam
running between the two infrared Leds, the unit
stops after six seconds, with the simulteneous
glowing of the YELLOW LED signalling the "Full
Bin" situation.
NOTE. The interruption of the light beam
between the two light sensors is immediately
signalled by the blinking of the BIN FULL
YELLOW LED located on the front of the
P.C. Board.
After about 6" of steady interruption of the
light beam the unit stops and the "Full Bin"
YELLOW LED glows steady.
The six seconds of delay prevent the unit
from stopping for any undue reason like the
momentarily interruption of the light beam
caused by the flakes that slides along the ice
spout before dropping into the bin.
As some ice gets scooped out from the storage
bin, the light beam between the two sensors
resumes and six seconds later the ice machine
restarts the ice making process - going always
through the 3' stand by - and the YELLOW LED
goes off.

REFRIGERANT CIRCUIT

The hot gas refrigerant discharged out from the
compressor reaches the condenser where, being
cooled down, condenses into liquid.
Flowing into the liquid line it passes through the
drier filter, then it goes all the way through the
ICE SPOUT
capillary tube where it looses some of its pressure
so that its pressure and temperature are lowered.
Next, the refrigerant enters into the evaporator
coil wrapped around the freezer inner tube.
The water being constantly fed at the interior of
the freezer inner tube, exchange heat with the
refrigerant circulating into the evaporator coil,
this cause the refrigerant to boil-off and evapora-
te, thereby it changes from liquid into vapor.
The vapor refrigerant then passes through the
suction accumulator and through the suction line
where the refrigerant exchanges heat with the
one flowing into the capillary tube (warmer) before
being sucked into the compressor to be
recirculated.
The refrigerant heat pressure is kept between
two pre-set values (8.5
by the condenser temperature sensor which has
its probe located within the condenser fins - in air
cooled versions.
This condenser temperature sensor, when
senses a rising of the condenser temperature
beyond the pre-fixed limit, changes its electrical
resistance and send a low voltage power flow to
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÷ 10 bar - 120 ÷ 140 psig)