Scotsman SCE170 - Manual (Page 12)

Electrical Sequence
This describes the sequence through a complete
cycle.
Freeze Cycle (curtain closed):
When the ON/OFF/CLEAN switch is at the ON
position, power is connected to the primary of the
transformer, which supplies power to the:
•
Control board and curtain sensor. If the curtain
is closed, the control board connects power to:
•
The compressor contactor coil. When the
contactor is energized, it connects power to the
compressor.
•
The control board also operates the water
pump and, if air cooled, the fan motor.
Timed Freeze:
After some ice has built up on the evaporator and
the suction line temperature has fallen, the cube
size thermostat contacts close, resulting in:
1. The Timed Freeze indicator light on the control
board glowing.
2. Power being connected to the freeze timer (in
the control board). After 4 minutes this internal
timer starts the harvest cycle by shutting power off
to the fan motor (if air cooled) and connecting
power to the:
•
Hot gas valve coil, opening the valve.
•
Purge valve coil, opening the valve.
Harvest/Shut Off:
The machine stays in the harvest cycle until the
curtain is opened by the passage of the ice sheet,
or until 7 minutes have passed. If after 7 minutes
of harvest time the curtain has not opened, the
control board switches the machine back into the
freeze cycle.
After the curtain has opened, the control board
keeps the machine in the harvest cycle for 7
additional seconds.
If the curtain re-closes, the machine goes back into
another freeze cycle.
If the curtain does not re-close, the bin control
board opens the circuits to all components except
the control circuit, stopping ice making.
Note: Both curtain indicator lights glow
when the curtain is completely closed.
Timed freeze indicator light glows when
cube size control closes.
Control Board
Located In Control Box
Timed Freeze
Indicator Light
Curtain Position
Indicator Lights
Fan & Purge
Valve Relay
Terminal
Strip
Curtain In Bin Full
Position (OFF)
Curtain In Normal
Run Position
Side View of Curtain Positions
SCE170
October 1998
Page 12