Mar Split Electrical/Refrigeration - Scotsman MAR 78 Service Manual

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3. MAR SPLIT - ELECTRICAL /
REFRIGERATION
The electrical circuit consists of drive motor,
water pump, water pressure switch, spout switch
and time delay safety device.
A. 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
disconnected 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.
B. 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 0,8 bar (10 psi) off and 1,2 bar
(17 psi). Cuts off complete unit and Resets
automatically.
C. Ice Spout Safety Switch
Located on top of the Ice Spout, the Safety
Switch is operated by a plate on top of the ice
chute by the ice backing up in the spout.
The switch will shut-off entire ice making
mechanism.
D. Liquid valve Delay timer
Delays belay 18' refrigerant liquid valve
opening at every start up of the ice maker.
Supplied.
E. Drum rotation delay timer
Delays drum STOP by 18' at every trip OFF of
the ice maker. Supplied.
F. 3 - phases monitoring relay
On the power IN, it checks and assures correct
rotation of the drive motor - evaporator drum.
Supplied.
G. Drum rotation control
It operates using the Hall effect sensor/
principle. In case the drum is not rotating at all
(or it rotates too slow - less then 1/4 turn every
30") such relay trips the unit OFF so to avoid
that in case of fiber keys breakage, the drive
motor - gear reducer and compressor can
operate with the drum OFF. Supplied.
H. Automatic Expansion Valve (A.E.V.)
The automatic expansion valve controls the
refrigerant when passing from the liquid line
to the evaporator. As the pressure decreases
on the low side, the expansion Valve open
and refrigerant escapes into the evaporator
drum channel where it absorbs heat from
water while evaporating. The valve maintains
a constant pressure in the evaporator coil
when the system is running indipendently of
the amount of refrigerant in the system.
This valve has an adjustment which may be
manually regulated to give the evaporator coil
the desired amount of refrigerant.
Turning the adjustment to the left,
counterclockwise, will increase the rate of
flow which is controlled by the pressure in the
evaporator.
When the compressor is not running the valve
remains closed as the low side pressure
will be high enough to close the expansion
valve.
- MAR Split 78-108-128 - is equipped with an
expansion valve having an orifice of 2,5 m/m.
- MAR Split 208-308 - is equipped with an
expansion valve having an orifice of 4,5 m/m.
I. Evaporator Drum
Refrigerant inlet/outlet takes place on left
side journal.
The drum body is covered by a jacket in
special stainless steel resistant to the water
corrosion.
The front edge of the scraping blade must
have a clearance of minimum 0.10 m/m from
cylinder metal jacket.
L. Refrigerant Seal System
Housed in the refrigerant inlet/outlet manifold
located on the evaporator drum left side
journal, is a leakproof joint. This joint is made
with seals that are carefully designed and
installed. The seals use two rubbing surfaces.
One surface tourns with the cylinder journal
and is sealed on it with on O ring of synthetic
material. The other surface is stationary and
fitted in its housing with leak-proof O rings.
The rubbing surfaces (optically flats) are made
of two different material that are: hardenend
steel for the rotating ring and graphite for the
stationary ring.
The rotating parts are:
a) the spring collar
b) the compression spring
c) the stainless steel seal ring with O ring.
The stationary parts are:
a) the graphitic ring with O ring
b) the stainless steel housing ring with gasket
and O rings.
M. Heat Exchanger
MAR Split 78, 108, 128, 208 and 308 have a
heat exchanger mounted in the suction and
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