Download Just What Is A Service Factor?

Just What Is A Service Factor?
This is a question we regularly receive on the Hotline. Understanding how the service factor affects an electric motor can be confusing, but it is not as complicated as it may seem. This guide
should help explain the term service factor and its relationship to Boat Hoist and Lift motors.
The National Electrical Manufacturers Association (NEMA) defines service factor in section MG1
- 1.43 of their manual as: "The service factor of an alternating current (AC) motor is a multiplier
which, when applied to the rated horsepower, indicates a permissible horsepower loading which
may be carried under the conditions specified for the service factor." The conditions under which
service factor may be applied are described in NEMA MG1 - 14.36 as: "When the voltage and
frequency are maintained at the value specified on the motor's nameplate, the motor may be
overloaded up to the horsepower obtained by multiplying the rated horsepower by the service
factor shown on the nameplate."
How does Service Factor (S.F.) Apply To A Motor?
KNOW BEFORE YOU BUY!
To determine the service factor horsepower of a motor, multiply
Marathon 3/4 HP Boat Hoist Motors
the nameplate horsepower (not amperage) by the service factor.
HP= .75
For example, if a 1 Hp motor has a service factor of 1.25, the
motor's service factor maximum horsepower is:
(1 HP) x (1.25 S.F.) = 1.25 Hp
SF = 1.00
Actual HP = .75
Leeson 3/4 HP Boat Hoist Motors
HP= .75
SF = 1.25
Actual HP = .93
STRONGEST!
AO SMITH 3/4 HP Boat Hoist Motors
HP= .75
SF = 1.00
Actual HP = .75
Marathon 1 HP Boat Hoist Motors
HP = 1hp
SF = 1.25
Actual HP = 1.25
STRONGEST!
Leeson 1 HP Boat Hoist Motors
HP = 1hp
SF = 1.00
Actual HP = 1.00
Anystandard 1 HP Boat Hoist Motors
AO SMITH
How Does Service Factor Relate to Motor Amps?
HP = 1hp
SF = 1.00
Actual HP = 1.00
Boat Hoist motors typically show two amperage values on the nameplate and in the specification sections of the equipment
guide. The first value labeled "amps" is the expected running amps when the motor is operated at rated voltage and nameplate horsepower loads. The second value labeled "SF Amps" is the expected running amps when the motor is operated at
rated voltage and service factor horsepower loads.
Even though amps may increase slightly when input voltage is higher or lower than nameplate voltage, the motor amp reading remains the simplest indicator of motor load. your motor amp reading is higher than nameplate service factor amps, the
horsepower load probably exceeds the service factor horsepower rating. If the AMPs are higher, continued use of the motor
will cause permanent damage to the motor. Review the equipment guide for possible trouble shooting.