Scotsman EC 105, Руководство по обслуживанию

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PRINCIPLE OF OPERATION
How it works
In the SCOTSMAN cube ice makers the water
used to make the ice is kept constantly in
circulation by an electric water pump which primes
it to the spray system nozzles from where it is
diverted into the inverted mold cups of the
evaporator. A small quantity of the sprayed water
freezes into ice; the rest of it cascades by gravity
into the sump assembly below for recirculation.
FREEZING CYCLE
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 capillary tube
where, due to the heat exchanging action, it
looses some of its heat content so that its pressure
and temperature are lowered as well.
Next the refrigerant enters into the evaporator
serpentine (which has a larger I.D. then the
capillary) and starts to boil off; this reaction is
emphasized by the heat transferred by the
sprayed water.
The refrigerant then increases in volume and
changes entirely into vapor.
The vapor refrigerant then passes through the
suction accumulator (used to prevent that any
small amount of liquid refrigerant may reach the
compressor) and through the suction line. In both
the accumulator and the suction line it exchanges
heat with the refrigerant flowing into the capillary
tube (warmer), before to be sucked in the
compressor and to be recirculated as hot
compressed refrigerant gas.
The freezing cycle is controlled by the evaporator
temperature sensor (which has its probe in
contact with the evaporator serpentine) that
determines the length of its first portion of the cycle.
When the temperature of the evaporator
serpentine drops to a pre-set value (small Red
LED ON steady) the evaporator sensor probe
changes its electrical resistance allowing a low
voltage current (15 volts) to flow to the P.C.
BOARD which in turn activates an electronic
timer.
The timer, which is built-in the P.C. BOARD,
takes over from the evaporator temperature
sensor, the control of the freezing cycle up to its
completion.
NOTE. The change of the electric potential
of the evaporator sensor with the consequent
activation of the timer (Time mode) is
signalled by the glowing-up of the RED LED
located in the front of the P.C. BOARD.
ATTENTION. In case, after 15 minutes
from the beginning of the freezing cycle,
the temperature of the evaporator sensor
probe is higher then 0
°
C (32
°
F) - small
Red LED still OFF - (shortage of
refrigerant, inoperative hot gas valve, etc.)
the P.C. BOARD switch OFF immediately
the unit with the simultaneous blinking of
the WARNING RED LED.
The length of this timed portion of the freezing
cycle is pre-fixed and related to the setting of the
first four DIP SWITCH keys.
The DIP SWITCH keys setting is made in
consideration of the type of condenser used and
size of ice cubes.
In Table B are indicated the various lengths of
the timed portion of freezing cycle in relation to
the different combinations of the DIP SWITCH
KEYS.
In Table A herebelow are illustrated 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
CONTACTOR COIL (EC 125-175 only)
and during the second phase of freezing cycle
(Time mode) they are joined by the
ELECTRONIC TIMER
The refrigerant head pressure, in the course of
the freezing cycle, ranges between 8.5 and 9.5
bars (110
÷
130 psig) in the air cooled version,
TAB. A
DIP SWITCH FACTORY SETTING COMBINATIONS (PER MODEL AND VERSION)
DIP SWITCH 1 2 3 4
ACM 45-55-85-125-175 A
ACM 45-55-85-125-175 W
ACM 105 A
ACM 105 W
5 6 7 8 9 10
FREEZING CYCLE DEFROST CYCLE
15/30"
W. PUMP
AIR/WATER
ON
ON
ON
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
OFF
OFF
ON
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
ON
OFF
ON
OFF