48
Pump Motors
Level 2
A.O.Smith
It may even lead to confusion. For exam-
ple, some A.O. Smith pump motor model
numbers begin with a letter: C =
Capacitor Start, S = Split Phase, K =
Capacitor Start and Run, P = Polyphase.
The next two numbers designate the
motor frame size: 48 = 48 Frame, 56 = 56
Frame. The next letter designates horse-
power: J = 1/2, K = 3/4, L = 1, etc. The
frame in the model number refers to the
motor's diameter of 5-5/8", not the NEMA
frame designation which may be 56C or
56J, etc. The horsepower letter designa-
tion is useless without the service factor.
If the nameplate is not legible, it will be
necessary to utilize pump data and sys-
tem voltage in order to select a replace-
ment.
C. Always install a new seal when reassembling
a pump or installing a replacement motor.
D. Be sure the motor is connected for the system
voltage. Most A.O. Smith dual voltage pump
motors are factory connected for the higher
voltage for two reasons. First, lower current
draw on high voltage allows the use of small-
er circuit wire, and reduces light flicker or
dimming when the motor starts. Second, if a
motor is connected for high voltage and low
voltage is applied, the motor will just hum, or
start and run very slowly until it trips the
overload. If a motor is connected for low volt-
age and high voltage is applied, the motor
burns out immediately.
E. Always be sure the motor is properly ground-
ed before applying power.
F.
Use an ammeter to assure that the motor is
not overloaded. The max load or SF (service
factor) amps on the nameplate should not be
exceeded.
