Electrical Sequence - Scotsman NME1250R Service Manual

NME1250R
ELECTRICAL SEQUENCE: A Model
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 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 be 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 machine shuts down.
Shut Down consists of:
The liquid line solenoid relay opens, lowering
the suction pressure.
The pump down pressure 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:
If the high pressure control (cut out) opens,
the machine will stop immediately (through the
relays on the circuit board). It must be manually
reset.
The pump down control switch will stop & start
the compressor.
The master switch is the manual control for the
complete machine, but it is not a service
disconnect.
June 1994
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