Scotsman MAR 106, Руководство по обслуживанию

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3. ELECTRICAL / REFRIGERATION
The electrical circuit consists of the compressor
motor, drive motor, water pump, condenser fan
motor and control (on air cooled version), main
controls (ON-OFF compressor Switch - Timer -
Contactor), safety controls - Thermal protection
for compressor - Hi and Lo pressure switches -
water failure switch, compressor and drive motor
delay timer, three phases monitoring relay.
A. Compressor unit - (see Technical Specifi-
cation Table for H.P.).
The compressor used on the MAR 56 - 76
- 106 - 126 is hermetic reciprocating type
compressors while on MAR 206 and 306 is
semihermetic type. All of them operating with
R 404a.
All compressors are equipped with a
crankcase heater element and are thermally
protected. Cooling is achieved with refrigerant
passing through suction valve and by a sepa-
rate fan motor on water cooled version only.
a) Compressor Crankcase Heater
Must be constantly energized particularly
during OFF period of ice maker operations.
The temperature provided by the heating
element into the crankcase prevents that
refrigerant dilutes with oil.
b) Compressor Thermal Protector
(Thermistor) on MAR 206 and 306
A thermistor is a solid state semiconductor
which permits or allows more electrons to
flow throught it as the material's temperatu-
re increases. Today thermistors are used
in place of a bimetal strip or in place of a
temperature sensitive power element as a
safety device in electric motors by stopping
the electric power flow to a motor if the
motor windings temperature increases to
the danger point.
B. Drive Motor
The evaporator drum drive motor is a three
phase motor of 1/2 HP wired for 380/220 Volts
50/60 Hz - 1,2/2,1 Amps - 1400 R.P.M. with
inherent thermal protector.
IMPORTANT - When this motor is discon-
nected or the entire unit is disconnected, it is
necessary - when resuming the electrical
connection to immediately make sure that
drive motor rotates clockwise facing the
unit front.
Failure to this, may result in wrong rotation of
evaporator drum with the risk of major
damages to the system.
C. Timer
It will be mainly used to pre-set the system
operation time in relation to the desired amount
to ice.
Therefore it takes the function of an Ice Level
Control in the storage area. This timer can be
remotely located if desired.
D. Hi Pressure Cut-Out Hand Reset
This high pressure control prevents operation
at high refrigerant pressure.
Shuts-off entire system in case of water failure
to condenser on water cooled units and of fan
motor failure on air cooled machines.
Factory cut-out setting are:
air cooled 34
±
2 bar (480
±
30 psi)
water cooled 30 bar (420 psi)
E. Water Failure Switch
This switch used as safety device when low or
interrupted supply water conditions are
encountered.
Operates on pressure between supply line
and feed line to water reservoir.
Range is 0.5 bar (7 psi) off and 0.8 bar
(12 psi) on.
Cuts off complete unit and Resets auto-
matically.
F. Lo-Pressure Cut-Out Automatical Reset
Lo Pressure Control prevents operation at
vacuum refrigerant suction pressure.
Shuts off entire system in case of refrigerant
failure in the system.
Factory setting cut-out: 0,2 bar.
G. Condenser Fan Motor
Air Cooled Units
The fan Motors used are permanent capacitor
type fan motors. Electrical supply to the fan
motors is 230 V, 50 Hz - 0,7 Amp. for
MAR 56, 76, 106, 126 10 and 306 - 0,9 Amp.
for MAR 206.
H. Fan Motor Pressure Control
MAR Air Cooled version are equipped with a
pressure control which is a reverse acting
automatic re-set control directly connected to
the fan motor. Its function is to maintain the
head pressure between the cut-in and cut out
setting values which are 15
÷
17 bar.
I. Control Console
Located on the front of the unit cabinet, is a
visual control console that monitors unit per-
formance automatically.
Any interruption or significant reduction in
water or electrical supply causes an instant
stop to the operation of the MAR flaker
system. At the same time a warning light is
activated on the control console telling the
user of the ice maker stoppage and also the
reason why.