(Page 2) FASCO FACTS
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INTRODUCTION
This edition of the long-standing informative Fasco
Facts booklet has been prepared by Fasco Distributing
Company as a helpful guide for the motor replacement
serviceman. The goal of this booklet is to provide a bet-
ter working knowledge of electric motors and related
disciplines. Being better informed provides a better
foundation for successful motor and blower replacement.
We encourage every service person to take basic pre-
cautions for their own safety as well as their customers
when installing or servicing motors. Power to the
equipment must be disconnected while the unit is being
serviced and all electric motors should be grounded.
The National Electrical Code and local electrical and
safety regulations should be followed at all times.
Keep in mind that even though this booklet provides an
abundance of information, there is much more infor-
mation available on motors from other sources such as
your local library. Depending on how much you wish
to learn about motors, the library can be an invaluable
source for the extended information. The only question
is how much do you want to learn? Have fun.
There are several types of fractional horsepower
motors. Each type performs certain jobs better than
the other types. The characteristics of a motor
designed to move air are completely different than
those of a motor used to drive a grinder, a pump, or
even a belt-driven application.
Fasco manufactures Permanent-Split Capacitor and
Shaded-Pole motors. These motors are normally used
with a fan blade or a blower wheel to move air. They
are used in applications associated with heating, air
conditioning, refrigeration, and ventilation. 3
CONTENTS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Power Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Motor Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Motor Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Motor Enclosures . . . . . . . . . . . . . . . . . . . . . . . . .8
Motor Bearings . . . . . . . . . . . . . . . . . . . . . . . . . .10
Thermal Protectors . . . . . . . . . . . . . . . . . . . . . . .12
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Condensation and Drain Plugs . . . . . . . . . . . . . .17
Motor Stacks and Windings . . . . . . . . . . . . . . . .18
Motor Efficiency . . . . . . . . . . . . . . . . . . . . . . . . .19
Horsepower . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Load Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Mechanical Characteristics . . . . . . . . . . . . . . . .22
Motor Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
High Slip Motors . . . . . . . . . . . . . . . . . . . . . . . . .25
Rating Motors With BTUs . . . . . . . . . . . . . . . . .26
Cooling Motors . . . . . . . . . . . . . . . . . . . . . . . . . .27
Motor Temperature . . . . . . . . . . . . . . . . . . . . . . .28
Speed Controls . . . . . . . . . . . . . . . . . . . . . . . . . .31
Removing Motors . . . . . . . . . . . . . . . . . . . . . . . .31
Motor Replacement . . . . . . . . . . . . . . . . . . . . . .32
Motor Selection . . . . . . . . . . . . . . . . . . . . . . . . . .33
Motor Selection Verification . . . . . . . . . . . . . . . .34
Motor Wiring and Rotation Reversing . . . . . . .36
Motor Installation . . . . . . . . . . . . . . . . . . . . . . . .39
Mounting Motors . . . . . . . . . . . . . . . . . . . . . . . .40
Contactor VA Rating . . . . . . . . . . . . . . . . . . . . . .42
Induced Draft Blowers . . . . . . . . . . . . . . . . . . . .43
Blower Wheels and Fan Blades . . . . . . . . . . . . .44
Fan Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48 POWER SUPPLIES
Voltages that power motors are either alternating current
(AC) or direct current (DC). Direct current provides a
current flow in only one direction. It is derived from the
alternating current. The alternating current simply is elec-
tronically routed to pass through a load in only one direc-
tion. Direct current is commonly used in applications that
require adjustable speed as in production line conveyors.
The properties of DC motors combined with the ease at
which direct current voltage can be created and adjusted
makes this type of drive system very popular. Alternating
current on the other hand provides current that flows in a
forward and reverse action. It does this 60 times per sec-
ond in the case of 60 hertz power. This power is either
single phase or 3 phase. Some common voltages used for
motors are shown below.
Single Phase Voltages
3 Phase Voltages
115 208
208
230
230
460
240
480
460
480
The flow of electric current can be compared to water
flowing through a hose. Voltage is the measure of electric
force in the power supply as the water pressure is the
hydraulic force in the hose.
The replacement and original motor voltages must be
identical. That is, 115 volts to 115 volts, 230 volts to 230
volts, etc. There is a voltage tolerance of +/- 10%, so a
230 volt motor will operate satisfactorily on a 208 volt
application and vice versa.
- Some older motors will be stamped 220 volts. In this
instance, either a 208 or 230 volt motor can be substituted.
- Oil and gas furnace direct drive blower motors are
usually 115 volts.
- Electric furnace direct drive blower motors are usually
230 volts.
- Condenser fan motors for residential air conditioning
units can be 208, 230, 277, or 460 volts.
4 FREQUENCY
MOTOR TYPES
The frequency rating of a power supply determines in part
the speed at which the motor will run. Frequency controls
the RPM of the rotating magnetic field which is what the
rotor follows. The formula for calculating motor RPM is:
RPM = (120)(Frequency)/Number of poles in the motor.
Note, 120 is a constant value.
The most commonly encountered air-moving motors are
Permanent-Split Capacitor and Shaded-Pole types. On the
outside, these two motor types look very much alike.
Sometimes, it may be necessary to disassemble the motor
to be replaced to properly identify its type. This is easily
accomplished by removing the thru bolts or clips, and tap-
ping the end shields off of the motor shell.
SHADED-POLE (SP)
CAPACITOR START
FACT
Used where low cost and low
starting torques are required. They are used
to drive blowers, bathroom ventilators,
range hoods, attic ventilators, down draft
blowers, fan coils, etc.
FACT
A Shaded-Pole motor can be rec-
ognized by the readily identifiable individ-
ual stator coil windings and the single cop-
per band (shaded coil) formed around one
side of each stator pole.
FACT
Shaded-Pole motors rotate toward
the shading band.
FACT
A higher starting torque motor
than the split phase motor. It is constructed
similar to the split phase motor. The key
exception is that the capacitor start motor
has a capacitor in series with the start wind-
ing to increase the start torque. The capaci-
tor is usually visible and mounted on motor
frame. Used in hard-to-start applications
such as compressors and pumps.
5 PERMANENT-SPLIT
CAPACITOR (PSC)
SPLIT PHASE
MOTOR TYPES (continued)
THREE PHASE
FACT
Used where higher starting
torques are needed than what a shaded-pole
motor will provide. They are also used
where higher efficiency motors are
required. Due to their efficiency, they have
become the motor of choice versus a shad-
ed-pole design. They are used to drive
blowers and all the other air-moving appli-
cations where shaded-pole motors are
found. They also are manufactured in high-
er horsepower ratings than what can be
found in shaded-pole designs. Therefore,
they get used in heavier duty applications
such as outside condensers.
FACT
A PSC motor can usually be rec-
ognized by the capacitor that is connected
to it. Also, between the main pole wind-
ings in the motor, there are pole windings
of finer wire. This is the auxiliary winding.
FACT
Higher starting torque motors than
a PSC. Suitable for belt drive furnace
blowers and belt drive ventilators. They are
more efficient than Shaded-Pole motors but
not as efficient as a PSC motor. These
motors have more defined RPM ratings.
They are usually rated at 3450, 1725, and
1140. They are not constructed to provide
the wide-range of multi-speeds as seen in
shaded-pole and PSC motors. Multi-speed
split phase motors are commonly built using
separate windings to provide other speeds.
This assures the speed sensitive start switch
will operate correctly in the motor.
The most efficient general purpose motor.
They are used in industrial or large com-
mercial applications where three phase
power is available.
6 MOTOR FRAMES
A motor frame type is a designation that a manufacturer
assigns to a motor to describe certain construction parame-
ters the motor will be built to meet. Any motors labeled
with a common frame type will be built with a similar set
of parameters such as motor diameter. A frame type will
mandate that a motor meet certain design parameters. For
example, in the case of integral horsepower mot