Scotsman NU100 Series, User Manual

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NU Undercounter Ice Maker User Manual How the Ice Maker Works
B9
How the ice maker works
For the NU100/150/220/300 ice maker, the
water for making ice is pumped into the spray
bar by a water pump. After flowing out of the
holes of the spray bar, then it will flow over the
surface of the evaporator plate with a constant
and even speed. On the evaporator plate,
some of the water will turn into ice; the
remaining water will flow into to the water
trough by gravity and will be re-circulated by
the water pump.
Freezing Cycle
The refrigerant gas discharged from the
compressor goes into the condenser, where it
is cooled and condensed into a liquid. The
liquid will flow into the drier filter and then it will
pass through the expansion valve. After that,
the pressure and temperature of the refrigerant
liquid will get much lower.
The refrigerant starts evaporating when it gets
into the serpentine pipes on the back of the
evaporator plate and cools the water flowing
over the front of the evaporator plate.
The refrigerant evaporates in the evaporator;
finally, the liquid changes into vapor and then it
will be pumped into the compressor where the
cycle starts again.
The 30 seconds before the freezing cycle starts
is the pre-cooling period, in this period, the
compressor is working, water pump is not, the
fan is working (controlled by the temperature
sensor on the condenser) and water inlet valve
is working (controlled by the water-level sensor
in the water trough).
The freezing cycle is controlled by the ice
thickness sensor, as long as the sensor
touches the ice for 30 consecutive seconds, the
ice thickness has reached the set point. Then,
the freezing cycle ends. The total length of
freezing cycle depends on the ambient
temperature and ice thickness setting.
Defrosting cycle
As soon as the controller detects the ice
thickness has reached the set point, the
machine will go into the defrosting cycle.
Hot refrigerant gas discharged from the
compressor directly flows into the serpentine
pipes of the evaporator, which bypasses the
defrost valve.
The refrigerant circulating in the serpentine
pipes heats the evaporator plate, which will
cause the ice cubes to melt. The ice cubes will
separate from the evaporator plate, then fall off
and go into the ice chute by gravity, finally
going into the storage bin.
When the ice has been harvested, the defrost
cycle will end. Then, the hot gas valve and
drain valve close (according to the PC board
setting); and the unit goes into its new ice
making cycle.