ELECTRICAL SEQUENCE
There are two circuits in the MFE400: 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 terminal strip in
the control box. From there, the line side power
is connected to the Master Switch.
••
When the master switch is closed, the power is
then connected to the Spout Switch. This
switch, located on the top of the ice chute, is
closed unless the ice chute has overfilled with
ice, it is an automatic reset.
••
From the spout switch the line side power now
is connected to the High Pressure Control
(water cooled). This control, connected to the
refrigeration system, is designed to open
whenever higher pressures are sensed. The
high pressure control is a manual reset.
••
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 it’s 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 ice chute. It is open when
there is ice on the portion of the control inside
the ice chute. Closing of the bin thermostat
begins the process of making ice, because the
line side power now goes to the compressor,
gearmotor, and if air cooled, the fan motor.
••
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 is connected to the neutral side of
the power supply, and the compressor begins
to run.
••
As the compressor runs, 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.
MFE400
May 1994
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