Scotsman MAR 78 Service Manual page 26

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liquid line to reduce flash gas in the liquid line,
to reduce liquid refrigerant in the suctionand
to subcool the liquid refrigerant thereby
increasing the operating efficiency.
N. Strainer Filter
All MAR Splits mount on liquid line a wiremesh
type of filter to prevent that screen of filter of
the expansion valve could becopme clogged
from dirt thereby stopping the refrigerant flow.
connections.
O. Motor Shaft Pulley
MAR Split units are generally equipped with
"Step pulley" and by changing the belt from
one groove to the other the speed of drum can
be changed.
MAR Machines are factory delivered with V
belt on smaller dia V groove of step pulley to
rotate the evaporator drum at the lowest
possible R.P.M. to obtain "THICK" (2 m/m
gauge) scale ice.
Normal drum R.P.M. for "THICK" ice
production are:
MAR 78 - 1.1 RPM
MAR 108 - 1.5 RPM
MAR 128 - 2.4 RPM
MAR 208 - 1.05 RPM
MAR 308 - 1.6 RPM
P. V Belt
V belts used on motor shaft pulley and gear
box are type:
MAR MAR MAR
78 108 128
X PZ 750 X PZ 900
When changing the V belt from one groove to
another, be careful to adjust it for proper
tension and alignement.
It should be snug not tight. A way to roughly
check belt tension is to apply a firm hand
pressure in the middle of the longest belt
span. If the belt is correctly tensioned, you
should be able to depress it about 5 m/m out
of line.
Q. Gear Reducer
The gear reducer is mounted on the right side
frame of evaporator drum basin to which it is
firmaly secured with four nuts.
The gear reducer bore in which passes the
drum shaft to be driven, has a keyway.
Two fiber keys are used to engage the gear
reducer to the drum shaft, they are in series in
the gear reducer bore, and shaft keyways.
Should the driving strain be excessive, the
two fiber keys will shear.
MAR 78, 108 and 128 are equipped with a
gear reducer having a ratio of 1/570.
MAR 208 and 308 have a gear reducer with a
ratio of 1/525.
MAR MAR
208 308
X PZ 937
The gear reducers are greased for life,
therefore they do not require any mainte-
nance.
R. Water pump / spay bar
Used only on FRESH WATER version the
water pump is mounted on the rear left side of
evaporator drum basin. It supplies water
under gentle pressure to the spray bar
located on top of evaporator drum.
S. Ice Level Control
Could not be necessary - It is subject to
corrosion in marine application. Supplied.
T. ON/OFF switch
The manual start-up or switching of the entire
system requires the attention of the operator
who may instantly keep control of the situation,
therefore it is preferable to any timed switch.
Supplied.
U. Warning Lights
Monitoring unit performance and interventions
of safety controls. Supplied.
V. Master Relay or Contactor
With electric coil connected in series with
safety controls for operation in safe conditions
of condensing and evaporating unit. Supplied.
W. Time Delay Relay
Mar Split series are equipped by two time
relay delay (KT1 and KT2) which control
operating condition of drive motor - gear
reducer and liquid solenoid valve opening.
On each ice maker start up, at first, drive
motor-gear reducer operates and KT1 liquid
solenoid valve delay by 18' its opening,
afterward opens and refrigerant pass through
the same (KT1 Yellow LED steady).
In case of any ice maker devices trip OFF,
KT2 relay keeps drive motor operating farther
for 18' in order to clean up the evaporator
from ice thus to assure easier/freely torque
forcing of the same on next start up (KT2
Yellow LED blinks).
X. Daily timer
Could not be necessary - Can be used in
place of the ice level control and of the ON/
OFF switch. Upon request.
Y. Liquid Line - Solenoid Valve
Necessary to stop refrigerant flow when not
desired. To be located on the liquid line past
the drier is electrically connected to
compressor contactor or relay to stop flooding
the evaporator and suction side during
compressor off periods. Supplied.
Z. Hi and Lo Pressure indicating gauges
Could not be necessary - They are subject to
setting alternations. Not supplied.
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