Basic Pump Operation and
Pumps used in pools and
spas are centrifugal type pumps. Water is pulled into the
center end fitting, called the suction, and sent out through the exit
fitting, called the discharge. In virtually every
implementation the discharge is at a 90 degree angle from the
suction. There are a few exceptions in this, namely the
Aqua-FloÂ® pump that is used in older 'Mr Spa' applications, and some
AcuraÂ® spa pumps. The flow-isolator shown above, is not on
all pumps, and is used to allow a higher pressurization of the pump
cavity. Without it, the output from the impeller will feed
back into the suction, reducing pump output.
Rotation speed is counter-clockwise (viewed from the front), typically
3450 RPM in a single speed pump, and 1725 and 3450 RPM in a
two speed version.
Pump motors are brushless, and the rotation speed is primarily
dependent upon the line frequency of 50 or 60 Hz. Because of
this design, the speeds can't be changed since the pump is 'hardwired'
for these specific speeds of operation.
The diagram above uses a 48 frame through bolt motor, which is the most
frequently used in the spa industry.
Motor manufacturers: A.O. SmithÂ®, EmersonÂ®, Franklin ElectricÂ®, General
ElectricÂ®, and MagnetekÂ®.
The business end of the spa pump, the part that moves the water, is
called the 'wet end'.
All 48 frame through bolt motors, with a threaded shaft, are generally
interchangeable among different manufacturers. That is, if
you remove the wet end from a GE motor, you can re-install it on any of
the other manufacturers pump motors with a similar horsepower rating.
The most commonly found problem in existing spa pumps, is the failure
of the pump seal assembly, located between the impeller and the volute
(back of the wet end). The end result is usually the
destruction of the impeller because of rust creeping back up the shaft,
and in severe cases, the pump bearing will fail, requiring replacement
of the bearing or the motor.
The cause for seal failure is usually the lack of proper water quality