Electrical Sequence - Scotsman NME650R Service Manual

ELECTRICAL SEQUENCE

Refer the wiring diagram as needed.
If the machine is switched off at the master switch,
but is otherwise ready to go, switching the master
switch to ON does the following:
The bin empty light on the circuit board goes on
There is a 15 second delay
If there is enough water in the reservoir, the
circuit board will allow the machine to start up.
Start up consists of:
The liquid line relay and auger motor relay
become energized, connecting power to the
liquid line solenoid coil and to the windings of
the auger motor.
The liquid line solenoid opens, raising the low
side pressure.
The pump down control closes.
The auger motor starts, and the centrifugal
switch closes, connecting power to the
compressor contactor coil.
The contactor is energized, connecting power
to the compressor, and the compressor starts.
As ice goes past the ice level sensors, the bin
empty light will stay on, and the machine will
continue to run, unless the ice stays between
the sensors for more than 15 seconds (bin full).
At that point, the bin empty light goes out, and
the machine shuts down.
Shut Down consists of:
The liquid line solenoid closes, lowering the
suction pressure.
The pump down control opens.
The compressor contactor opens
The compressor stops
The auger motor is run by the circuit board for 2
more minutes, clearing out ice in the
evaporator, and then
The auger motor relay opens, and the auger
motor stops.
If the ice level sensor is clear (bin empty) for more
than 15 seconds, the machine will start up again.
Another purpose of the circuit board is to turn the
machine off if there is not enough water in the
machine.
When the water level in the reservoir falls below
the water level sensor, the machine will "shut
down"
When the water refills the reservoir, the
machine will start up again.
Separate from the circuit board:
The high pressure control will stop the machine
immediately if it opens. It is manually reset at
the control and at the reset switch on the circuit
board.
The master switch is the manual control for the
complete machine, but it is not a service
disconnect.
August 1993
Page 15
NME650R