Scotsman CME855A - Manual (Page 15)

COMPONENT DESCRIPTION
Compressor Contactor
The compressor contactor carries the compressor
line current. The compressor contactor coil has
power whenever the ice machine is making or
harvesting ice.
Cube Size Control
This reverse acting (closes on temperature fall)
thermostat determines how long the freezing cycle
will be. The cube size control closes it’s contacts
when the evaporator & suction line cools to the set
temperature. When the cube size control closes, it
connects power to the timer motor. A variation in
heat load (either ambient air or incoming water
temperature) will affect the efficiency of the
refrigeration system, and that will vary the length of
time it takes the evaporators to cool to the
temperature at which the cube size control is set to
close, which, in turn, will affect the overall cycle
time. See CUBE SIZE ADJUSTMENT BEFORE
attempting to adjust the control.
Relay
The multi-function, three pole, double throw, relay
plugs into a socket on the printed circuit board in
the control box. When the relay coil has power, the
machine is in a freeze cycle, and when power is
removed from the coil, the machine will be in the
harvest cycle.
The relay also by-passes the bin control during the
harvest and freeze cycles, preventing the ice
maker from shutting off in the middle of a cycle.
The bypass action allows only complete freeze
and harvest cycles; the only time that the ice
maker can shut off on bin control is as the end of
the harvest cycle.
Timer - Timer & Switch Assembly
The timer begins to turn when activated by the
cube size control. The outer surface, or large
diameter lobe of the timer cam, determines the
length of time for finish freezing of the ice cubes,
while the inner surface, or small diameter lobe,
determines length of the harvest cycle. The
single-pole, double throw microswitch on the timer
controls the power to the plug in relay coil, making
it either the freezing or harvest cycle. The
microswitch is actuated by the cams connected to
the timer motor. The timer cam can be adjusted to
vary the defrost time, as required. One complete
rotation of the cam will take eight minutes.
Hot Gas Solenoid Valve
The hot gas solenoid valve opens only during the
harvest cycle. When it opens, it diverts the hot
discharge gases so that they flow directly into the
evaporator plates, by-passing the condenser and
thermostatic expansion valve. The hot gases warm
the evaporators, releasing the ice cubes from the
ice cube molds. The hot gas solenoid valve is
installed in a branch of the discharge line, and
when the timer switches the ice machine into the
harvest cycle, the energized solenoid coil lifts the
valve stem within the valve body, allowing the hot
discharge gas to be diverted to the evaporators.
High Temperature Cut Out
This temperature sensor is located next to the hot
gas valve, on the outlet side.
Cut Out is 140
o
F., Cut In is 110
o
F.
During normal operation, it does not affect the ice
machine, but it will shut the machine off if the hot
gas line overheats. It is an automatic reset.
CME855A & CME1000A
October, 1994
Page 15