Scotsman EC 45 Service Manual page 34

Page 34
An automatic hi pressure control activates the
second coil of the water inlet solenoid valve so to
supply a metered amount of water to the
condenser and drop down its temperature and
pressure.
K. HOT GAS SOLENOID VALVE
The hot gas solenoid valve consists basically in
two parts: the valve body and the valve coil.
Located on the hot gas line, this valve is energized
through the micro processor of P.C. BOARD
during the defrost cycle as well as during the
water filling phase.
During the defrost cycle the hot gas valve coil is
activated so to attract the hot gas valve piston in
order to give way to the hot gas discharged from
compressor to flow directly into the evaporator
serpentine to defrost the formed ice cubes.
L. FAN MOTOR (Air cooled version)
The fan motor is controlled through the P.C.
BOARD and the TRIAC by the condenser tempe-
rature sensor. Normally it operates only during
the freezing cycle to draw cooling air through the
condenser fins. In the second part of the freezing
cycle, the fan motor can run at intermittance as
the condenser pressure must be kept between
two corresponding head pressure values.
M. COMPRESSOR
The hermetic compressor is the heart of the
refrigerant system and it is used to circulate and
retrieve the refrigerant throughout the entire
system. It compresses the low pressure refrigerant
vapor causing its temperature to rise and become
high pressure hot vapor which is then released
through the discharge valve.
N. HI PRESSURE CONTROL - EC 45-55-85-105
(Water cooled version)
Used only on the water cooled versions it operates
to keep between 9.5 and 10.5 bars (135 ÷ 150
psig) the hi-side or discharge pressure of the
refrigerant system by energizing the coil of the
water inlet solenoid valve that control the cooling
water flow to the condenser.
O. WATER REGULATING VALVE - EC 125-175
(Water cooled version)
This valve controls the head pressure in the
refrigerant system by regulating the flow of water
going to the condenser.
As pressure increases, the water regulating val-
ve opens to increase the flow of cooling water.
P. CONTACTOR - EC 125-175
Placed outside of the control box it is controlled
by the P.C. BOARD in order to close or open the
electrical circuit to the compressor.
Q. WATER DRAIN SOLENOID VALVE
The water drain solenoid valve, electrically
connected in parallel to the water inlet and to the
hot gas solenoid valves, is energized for all the
length of the defrost cycle.
By means of the water pump, that remains
energized for 15 seconds at the beginning of the
defrost cycle, it allows the drain out of all remaining
water (rich of minerals deposited during the
previous freezing cycle) from the sump tank.
By doing so it allows to the ice maker to make
every new freezing cycle with new fresh water,
avoiding thereby the accumulation of sediments
and scales, which soon or later will cause the
partial or total clogging of the water system on the
unit.
R. SEALED WATER RESERVOIR
Located on the bottom side of the unit, it is used
to collect all water coming from the:
• Overflow
• Water Drain Valve
• Storage bin
On its top cover are secured two metal pins
(Water Level Sensor) connected to the PWD PC
Board.
S. PWD PC BOARD
Located on the front side of the machine, it is
used to energise the Water Drain Valve any time
the level of the water into the Sealed water
Reservoir reaches the upper metal pins (low
power electrical circuit closed through the water).
The water pump is kept energised by the PWD
PC Board according to the setting of its trimmer.
WATER
WATER
LEVEL LEVEL
SENSOR
SENSOR
OPTICAL OPTICAL
CONNECTOR
IN OR OUT IN OR OUT
- +
TRIMMER
TRIMMER
TIME WATER TIME WATER
PUMP ON
PUMP ON
TRIMMER TRIMMER
- +
WATER
WATER
SENSIVITY SENSIVITY
OPTICAL
OPTICAL
CONNECTOR
IN OR OUT
IN OR OUT
A second trimmer is used to increase the signal
(low power current) received by the water level
sensor of the Sealed Water Reservoir in order to
overcame the problem of low electrical
conductivity of very soft water.
WARNING: to assure the correct operation
of the Water level sensors, the water must
have a minimal electrical of 10
A Buzzer, on the PWD PC Board, is used to alert
the end user in case the water level sensor
transmit the signal to the PWD PC Board for
more then 5 minutes continuously so to avoid
any possibility of water overflowing. In the
meantime the Main PC Board will switch OFF the
entire machine at Storage Bin Full.
T. WATER DRAIN PUMP
Placed beside the Sealed Water Reservoir is
used to pump out the water contained into the
tank. It is energised, by the PWD PC Board, for
just few seconds.
U. CHECK VALVE
Placed on the discharge hose of the water pump,
it prevents the coming back of the pumped out
water.
Page 34
RELAY RELAY
BUZZER BUZZER
POWER IN & OUT
CONNECTION
CONNECTION
TRANSFORMER
TRANSFORMER
µ
S.