A.O. Smith ST1302 Manual page 5

Pump Motors
The overloads or protectors used on pump
motors are tested on an eighteen day locked cycle
test. The eighteen days simulates a two week
vacation plus weekends and a couple of extra
days. During the test, the motor shaft is locked
and power is applied to the motor. Since the
motor cannot start, it will heat up rapidly and
the overload will take it off line. After the over-
load resets, the cycle is repeated. The motor
must operate at the end of the test.
If a motor does not operate because the over-
load has failed you should look for other prob-
lems. Its failure is often a symptom of another
problem.
The pumps are designated centrifugal since the
motor spins an impeller which moves the water
by centrifugal action.
Pumps used in these applications are classified
as centrifugal pumps. A centrifugal pump
derives its name from the principal known as
centrifugal force.
A centrifugal swimming pool pump, in its sim-
plified form, consists of two components. One
component is stationary and serves as the hous-
ing. It is known as the volute. Inside the volute
is the rotating component known as the impeller
which is driven by a motor. The motor is the
"work horse" of the pump while the impeller is
the "cartwheel" that moves the water.
Level 2
3
A.O.Smith