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Since Franklin Electric was the motor manufacturer for every
American submersible pump company in the United States
up until recently; the information below will relate to only
one brand of motor.
The two wire Franklin motor has three wires. Two of
these wires are black and connect directly to the power source.
The third wire is the green ground wire.
The three wire motor has four wires. A red (start
wire) a black, a yellow and the green ground wire. The red,
black and yellow all connect to their perspective terminals
in a control box which is installed above ground in a convenient
location. The green is connected to the ground terminal. The
other two terminals in the control box are the L1 and L2 connections
which accept the power from the electric company. In this
control box are a start capacitor, a relay and sometimes an
overload protector and run capacitor.
The two wire motor has a biac switch that energizes the start
winding in the motor to get it up to speed. When the motor
is almost at normal RPMs, the biac switch disconnects the
start winding for the remainder of that cycle.
The three wire motor uses the start capacitor along with
the start winding to get the motor nearly up to speed, then
the relay points open and disconnect the start winding and
the start capacitor until needed again. In the case of the
run capacitor, it is in line all the time and does not need
a relay to disable it.
When a pump gets locked up due to sand or grit, the three
wire motor depends on the start capacitor to have enough strength
to kick start the pump. But in the case of the two wire, if
the pump is locked up, the biac switch will kick the motor
in a reverse direction then back in the foreward direction
to try to break the pump loose. Of coarse if the pump is hopelessly
froze up, it will have to be pulled and serviced.
The cost for a two wire pump or a three wire with/control
box is usually the same . But for my money, I will stick with
the two wire. It has been proven to last longer, it is easier
to install and you don’t have to look for a mounting spot
for the control box.
Two wire motors are available in 1/2, 3/4, 1 and 1.5 horsepower
only. Two, three and five horse are three wire only.
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