Electrical Sequence - Scotsman NME1854R Service Manual

ELECTRICAL SEQUENCE

There are 7 indicator lights on the control board:
·
WTR-OK (Water OK).
Glowing. Glows when there is water in the
reservoir.
·
PWR-OK (Power OK).
Glowing. Glows when the control board has
power and is functional.
·
Service. Red. Normally Off.
·
Freeze. Red. Normally glowing when making
ice.
·
Bin Full. Red. Normally Off when making ice.
·
LED1. White. Located next to the board's
Compressor Relay. Normally Glowing when
making ice.
·
LED3. White. Located next to the board's Auger
Motor Relay. Normally Glowing when making
ice.
If the machine is switched off at the mode switch,
but is otherwise ready to go, switching the mode
switch to ON does the following:
·
The PWR-OK light glows.
·
If there is water in the reservoir the WTR-OK
light glows.
·
After 10 seconds the Freeze, LED1 and LED3
lights glow and the machine starts up.
Start Up:
·
The compressor relay and auger motor relay
become energized, connecting power to the
windings of the auger motor and liquid line valve
coil.
·
The liquid line valve opens, refrigerant flows to
the expansion valve.
·
The pump down pressure switch closes
connecting power to the contactor coil
·
The contactor is energized, connecting power to
the compressor, and the compressor starts.
·
As ice is made it passes between the ice level
sensors but because it is not a continuous
stream it only interrupts the sensor's infrared
beam momentarily. The bin full light remains off
and the machine stays on until ice builds up in
the bin and blocks the path between the
sensors for 6 seconds or longer. When that
occurs the bin full light glows and the machine
shuts down.
Green. Normal =
Green. Normal =
January 2000
NME1854R & FME2404R
Shut Down:
·
The compressor relay opens, LED1 goes out.
·
The liquid line valve closes, stopping refrigerant
flow.
·
The pump down control opens after the suction
pressure falls to its cut out point.
·
The compressor contactor opens
·
The compressor stops
·
The auger motor stays on for 1 more minute,
clearing out ice in the evaporator, and then
·
The auger motor relay opens, LED3 goes out
and the auger motor stops.
The liquid line valve will not reopen until 2 minutes
or more have passed after the last shut down.
If the path between the ice level sensors remains
clear for more than 10 seconds the ice machine
will restart.
Control Board Protection Devices
·
When the water level in the reservoir falls
below the water level sensor's tip, the WTR-OK
light goes out and the machine shuts down.
When water refills the reservoir the WTR-OK
light glows and the machine starts up again.
·
If the auger drive motor current becomes
excessive the liquid line valve and auger drive
motor will be switched Off and the Service light
will blink. The control board will restart the auger
drive motor in 4 minutes. If during the first 60
seconds after restart the auger motor current
stays within limits, the liquid line valve is
reopened and the machine returns to normal
operation. If the auger motor's current is
excessive within 60 seconds after the restart,
the process will be repeated once more. If
during that try the current is still excessive the
machine shuts down and must be manually
reset. The service light will then be glowing
continuously.
To Reset: Disconnect and reconnect power to
the ice machine.
Other Protection Devices:
·
If the high pressure cut out switch opens the
machine will stop immediately. It will
automatically reset when the high pressure falls
below its cut in point.
The mode (on - off) switch is the manual control
for the complete machine, but it is not a service
disconnect.
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