Principle Of Operation - Nordcap SDE 100 L Bedienungsanweisung

PRINCIPLE OF OPERATION

In the SIMAG 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 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
thermostat (which has its bulb in contact with the
evaporator serpentine) that determines the length
of its first portion of the cycle.
When the temperature of the evaporator
thermostat bulb drops to a pre-set value, the
evaporator thermostat changes its contacts (from
3-4 to 3-2) suppling power to the finishing timer
that takes 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 freezing cycle are:
COMPRESSOR
CONTACTOR COIL (SDN85-145-215)
FAN MOTOR (in air cooled version)
WATER PUMP
and during the second phase of freezing cycle
(Time mode) they are joined by the
TIMER
On the SDE64-SDE84-SDE100-SDE170-SDE220
air cooled the refrigerant head pressure, in the course
of the freezing cycle, ranges between 8 ÷10 bars
SDE 64, 8 ÷9,5 bars SDE84, 18-14,5 bars SDE 100
15-19,5 bars SDE170, 16-20 bars SDE 220 being
controlled by the hi-pressure control.
When the discharge pressure rises up to a pre
set value, the pressure control closes its electrical
contacts suppling power to the FAN MOTOR.
As soon as the discharged refrigerant pressure
drops, the pressure control opens its contacts to
temporarely de-energize the fan motor. On others
air cooled models (SDE30÷50) the fan motor is
constantly activated and retain the head pressure
between 8÷10 bars (110÷140 psig).
On the models from SDE30 ÷64 water cooled
version the same hi-pressure control is used to
intermittently energize a water solenoid valve
located on the water supply line to the condenser.
On the other models SDE84-100-170-220, in water
cooled version, the discharge pressure is kept
constant by the water regulating valve that meters
the water flow to the condenser.
NOTE. In case of shortage/insufficient cooling
water or air condenser dirty, the operation of
the safety device by hand reset will stop the
machine as soon as the temperature reach
70/75 ° C (160/170 ° F) or the corresponding
pressure. After eliminated the cause of the
stop, put the machine in operation by
pushing the reset button of the safety
thermostat or pressure switch across the
holes in the down/right side of the front panel
or removing it.
At the start of the freezing cycle the refrigerant
suction or lo-pressure lowers rapidly to 0,8 bars
SDE30÷SDE84, 3,6 bars SDE100-SDE 170
and 2,4 bars SDE 220 then it
declines gradually - in relation with the growing of
the ice thickness - to reach, at the end of the
cycle, approx. 0,1 bars SDE30÷SDE84, SDE 100
2 bars, 1,5 bars SDE170, and 1,3 bars
SDE220 with the cubes fully formed in the
cup molds.
The total length of the freezing cycle ranges from
18 to 20 minutes.
DEFROST OR HARVEST CYCLE
As the electric timer has carried the system
throughout the second phase of freezing cycle,
the defrost cycle starts.
NOTE. The length of the defrost cycle is pre-
determined by the setting of timer
.
In case it is possible to modify the defrost
cycle length through its setting screw.
ATTENTION. The defrost period is the
most critical 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 3 minutes at the most.
The electrical components in operation during
this phase are:
COMPRESSOR
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