Electrical Sequence - Scotsman AFE424W1A Manual

AFE424

Electrical Sequence

There are two circuits in the AFE424: one is a
series circuit with several switches connected in
series to the compressor. The other is a parallel
branch of the series circuit, controlling the gear
drive motor.
·
The series circuit begins at the contactor in the
control box. From there, the line side power is
connected to the Master Switch.
·
From the master switch the line side power is
connected to the High Pressure Cut Out.
·
The line side power is also connected, in a
parallel circuit, to terminal 1 of the Auger Delay
pressure control. This pressure control,
connected to the low side of the refrigeration
system, is designed as a by-pass circuit to the
auger drive motor whenever the low side
refrigerant pressure is at its normal ice making
range. At start up, the contacts between
terminals 1 and 2 are open. The line side power
does not pass any further through the auger
delay pressure control until the compressor
starts and the low side pressure drops.
·
The next control the power is connected to is
the Low Water Pressure Control. This switch is
designed to open should the water pressure to
the machine drop too low.
·
The next control is the Bin Thermostat. It is
closed when there is no ice on the portion of the
control inside the thermostat bracket. It is open
when there is ice on the portion of the control
inside the thermostat bracket. Closing of the bin
thermostat begins the process of making ice,
because the line side power now goes to the
compressor contactor coil.
·
Power is initially connected to the gearmotor
through contacts 3 and 2 of the auger delay
pressure control. This causes the auger motor
to start and run. At the same time, if the
centrifugal switch on top of the gearmotor
closes (meaning the motor is at full speed) the
compressor contactor coil is connected to the
neutral side of the power supply, and the
compressor begins to run.
·
As the compressor operates, the low side or
suction pressure begins to fall, when it reaches
a preset point, the contacts within it move,
opening 3 and 2, then closing 1 and 2. The
power for the gearmotor is then connected to a
point in the series circuit ahead of the low
pressure control, the low water pressure control
and the bin thermostat, so that if any of these
open, the gearmotor will continue to run,
pushing ice out of the evaporator.
April 2010
Page 9