GB
22
PRINCIPLE OF OPERATION
In the 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 molds of the evaporator. A smoll quan-
tity 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 compres-
sor reaches the condenser where, being coole down, con-
denses into liquid. Flowing into the liquid line it passes
through the drier filter, then it goes all the way throught 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 tranferred
by the sprayed water.
The refrigerant then increases in volume and changes
entirely into vapor.
The vapor refrigerant then passes throught the suction
accumulator (used to prevent that any small amount of liq-
uid 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 inthe com-
pressor and to be recirculated as hot compressed refrig-
erant gas.
The freezing cycle is controlled by the evaporator thermo-
stat (Which has its bulb in contact with the evaporator ser-
pentine) that determines the length of its portion of the
cycle.
When the temperature of the evaporator thermostat
changes its concts (from 3-4 to 3-2) suppling power to the
finishing timer that takes the control of the second timed
portion of the control of the second timed portion of the
freezing cycle up to its completion.
The length of this second timed portion of the freezing
cycle is pre-fixed and related to the setting of the upper
part of the timer cam.
The electrical components in operation during the freez-
ing cycle are:
COMPRESSOR
FAN MOTOR (in air cooled versio)
WATER PUMP
CONCATROR COIL
and during the second phase of freezing cycle (Time
mode) they are joined by the TIMER
The refriferant head pressure, in the course of the freez-
ing cycle, ranges between 9/7 bars.
On the air cooled version, the FAN MOTOR. Is working
during freezing cycle.
On the water cooled version the same hi-pressure control
is used to itermittently energize a water cooled version,
the discharge pressure is kept constant by the water reg-
ulating valve that meters the water flow to the condenser.
NOTE. In case of shortage of water to the condenser
or failure of the water solenoid valve a second “safe-
ty“ condenser thermostat, with the bulb in contact with
the tube of the liquid refrigerant, switch OFF the unit
operation as soon as its temperature reaches 35°C
(150°F).
The unit will resume automatically its operation when
the temperature of the condenser thermostat bulb
drops down by 10°C (18°F).
At the start of the freezing cycle the refrigerant suction or
lo-pressure lowers papidly to 1 bar then it declines grad-
ually - in relation with the growing of the ice thickness - to
reach, at the end of the cycle, approx. 0,2 bar with the
cubes fully formed in the cup molds.
The total length of the freezing cycle range from 18 to 20
minutes.
DEFROST OR HARVEST CYCLE
As the electric timer has carried the system throughhout
the second phase of frezing cycle, the defrost cycle starts.
NOTE. The length of the defrost cycle is predeter-
mined by the setting of the lower portion of the timer
cam.
In case it is possible to modify the defrost cucle length
through its setting screw.
ATTENTION. The defrost period is the most criti-
cal for the icemaker main components expecially
the compressor. To avoid to abuse of them it is
strongly recommended to limit the harvest cycle
extension to 4 minutes at the most.
The electrical components in operation during this phase
are:
COMPRESSOR
WATER INLET SOLENOID VALVE
HOT GAS SOLENOID VALVE
TIMER MOTOR
Содержание N21
Страница 16: ...GB 30 ELECTRIC DIAGRAM N21...
