Scotsman MV 12 Service Manual page 23

Page 23
3. Compressor Contactor
Located in the control box, the compressor
contactor functions to carry the compressor line
current. The contactor is wired to receive power
from the P.C. Board.
4. Ice Thickness Sensor
Located in the front upper right side off the
evaporator, the sensor is made with two metal
reeds in which passes power at low voltage. The
two metal reeds, which are individually insulated,
are set, through a setting screw, to maintain
a minimum clearence from the evaporator
(5÷7 m/m). Once ice is formed into each mold
and is thick enough to fill-up that minimum
clearance existing between the two sensor reeds,
and the evaporator, the water that cascades over
the ice has gradually approached to make contact
between the two sensor reeds.
It is enough that this contact remains there for
about 10 seconds that the P.C. Board receives
the signals to put the ice machine on defrost.
5. Magnetic Switch
Located in the front of the evaporator front plastic
deflector (one for each one on model MV 50), this
switch sends a pulse to the P.C. Board which
switches the machine back in the freezing cycle.
On model MV 50 after the pulse sent by the
second magnetic switch, signalling the dropping
into the bin of the second slab of ice, the P.C.
Board restarts a new freezing cycle.
NOTE: In case the P.C. Board does not
receive the pulse from the second
microswitch, after 40 second from the first
pulse, it will switch in any case the unit from
defrost to freezing cycle.
6. Hot Gas Solenoid Valve
The Hot Gas Solenoid Valve functions only during
the Harvest Cycle, to divert the hot discharge gas
from the Compressor, bypassing the Condenden-
ser and thermostatic expansion valve, for direct
flow to the Evaporator Platen Assembly to release
ice cubes from the ice cube molds.
The Hot Gas Solenoid Valve is comprised of two
parts, the Body & Plunger and the Coil assembles.
Installed in the discharge line of the Compressor,
the energized solenoid coil lifts the valve stem
within the valve body to cause the hot discarge
gas to be diverted when the ice Thickness sensor
has signalled to the P.C. Board to start the
Harvest Cycle.
7. Condenser temperature sensor
The condenser temperature sensor probe
(located in contact with the condenser tube coil)
detects the condenser temperature variations
and signals them by supplying current, at low
voltage, to the P.C. BOARD.
In the air cooled versions, in relation to the
different current received, the micro processor of
the P.C. BOARD supplies, through a TRIAC, the
power at high voltage to the fan motor so to cool
the condenser and to reduce its temperature.
In case the condenser temperature rises and
reaches 65°C (150°F) the current arriving to the
micro processor is such to cause an immediate
and total stop of the machine operation with the
blinking of the Red LED.
8. High Pressure Control
The high Pressure Control, a safety control, is
factory set to cut-out, at 28 bar and cut-in at 22
bar. The control, functions as a precautionary
device to shut OFF electrical power to Icemaker,
should a loss of water occur to the water cooled
Condenser or a burnt out of one of both the fan
motors on air cooled versions. The high Pressure
Control is manual reset with reset button located
on the rear side of the machine and a monitoring
light on the Front Console Panel.
9. Water Regulator Valve
(Water Cooled Models)
The Water Regulator Valve functions maintain a
constant Compressor head pressure, by
regulating the amount of incoming water flow
through the Condenser, on water-cooled models.
The valve operate through the refrigerant system
high side pressure. Rotating the adjusting screw
located on top of the valve, can INCREASE or
DECREASE the water flow through the water-
cooled Condenser, which in turn, will DECREASE
or INREASE the Compressor operating head
pressure.
10. Water Distribution System
The Water Distribution System function to eventy
supply water to all cells of the evaporator plate.
The water pump pumps water from the sump to
the tee. From there water is channeled through
the vertical tygon tube to the water distributors,
above the evaporator plate, and from the holes in
the distributor tube water flows to the cells on one
side of the evaporator plate.
Gravity flow returns the unfrozen excess portion
of water to the sump reservoir for recirculation.
11. Water Drain Solenoid Valve
The Water Outlet Solenoid Valve functions in
conjunction with the water pump to flush-out the
sump assembly at the beginning (first 20") of
every harvest cycle. This action cleans-up and
rinses the sump during each harvest cycle pre-
venting dangerous water minerales concentration.
12. Thermostatic Expansion Valve
(TXV) (2 on model MV 50)
The Thermostatic Expansion Valve regulates
the flow of refrigerant to the evaporator and
reduces pressure of liquid refrigerant from
condensing pressure to evaporating pressure.
13. Water pump
The water pump primes the water from the sump
to the water distributor tube/s and through the
distributing holes it cascades down onto the
evaporator cells by gravity so to be frozen into
clear ice cubes. The water pump remains off
during the first minute of the freezing cycle (to
avoid any cavitation problem) while it's kept
running during the first 20" of defrost/harvest
cycle to drain out (purge) the remaining water
from the sump (reach in mineral salts).
Page 23