Nick Gromicko, CMI®
A fan attached to a room’s ceiling is known as a ceiling fan. Like other fans,
it is used to provide comfort for building occupants by circulating air within a room.
Fun Facts About Ceiling Fans
- An adult human cannot be decapitated by a ceiling fan,
according to the TV show "MythBusters." A powerful, industrial-strength fan might be able to damage a skull
or slice a person’s neck, however.
fans were first used in the United States in the 1860s. They were powered by a system of belts driven by a stream of running
- Unlike air conditioners, fans
do not actually cool the air, which is why they merely waste electricity when they circulate air in an unoccupied room.
Ceiling Fan Components
A ceiling fan is comprised of the following parts:
motor: varies with the size of the fan and its application;
- blades: typically, two to six spinning, precision-weighted blades made from metal,
wood or plastic; industrial fans typically have three blades, while residential models have four or five;
- blade irons: connect the blades to the motor;
- safety cable: on heavy fans, these are required
to hold the fan in place in case the support housing fails;
- flywheel: connects the blade irons to the motor;
- ceiling mount: designs include ball-in-socket and J-hook;
- downrod: used where ceiling fans are suspended from high
- motor housing: protects
the fan motor from dust and its surroundings; may also be decorative; and
- lamps: may be installed above, below or inside the motor housing.
Common Fan Defects
- The fan falls. A ceiling fan that breaks free from its ceiling mount can be deadly. Fans must be
supported by an electrical junction box listed for that use, according to the National Electric Code, and a fan brace box
will need to be installed. While a particular junction box might support a fully assembled fan, during operation, it
will exert additional forces (notably, torsion) that can cause the support to fail. Homeowners often overlook this distinction
by carelessly replacing light fixtures with ceiling fans without upgrading the junction box, which should clearly state whether
it’s rated to hold a ceiling fan.
fan wobbles. This is a common and distracting defect that is usually caused when fan blades are misaligned from one another.
Specific problems stem from minute differences in the size or weight of individual blades, warping, bent blade irons, or blades
or blade irons that are not screwed in tightly enough. The ceiling mount may also be loose. Wobbling is not caused by
the ceiling or the particular way that the fan was mounted. Wobbling will not cause the fan to fall, and there have been no
such reports. Wobbling can, however, cause light fixture covers or shades to loosen and potentially fall. These items should
be securely attached, with all screws tightly set in place. An easy way to tell if the blades are not on the
same plane is to hold a yardstick or ruler against the ceiling and measure the distance that the tip of each blade is
from the ceiling by manually pushing the blades. A homeowner can carefully bend the misaligned blade back into place. Blades
can also be corrected in this way if measurement reveals that they are not equidistant from one another.
- There is inadequate floor-to-ceiling blade clearance. No part of
the fan blades of a residential ceiling fan (usually having four or more blades) should be closer than 7 feet from the
floor in order to prevent inadvertent contact with the blades. Downward air movement is maximized when the fan blades are
around 8 or 9 feet from the floor. For high ceilings, the fan may be hung to a desired height. Low-profile fan models
are available for ceilings that are lower than 8 feet from the floor. Also, fan blades should be at least 18 inches from
walls. For commercial ceiling fans (usually having three blades), no part of the fan blades should be closer than 10 feet from the floor in order to prevent inadvertent contact
with the blades. Underwriters Laboratories UL 507 Section 70.2.1 says:
"The blades of a ceiling-suspended fan shall be located at least 3.05 m (10 feet) above the
floor when the fan is installed as intended."
Underwriters Laboratories makes exceptions if the fan blade edges are thick and the fan is turning slowly.
- Blades are turning
in the wrong direction. In the winter months, the leading edge of the fan's blades should be lower than the trailing edge
in order to produce a gentle updraft, which forces warm air near the ceiling down into the occupied space below. In the
summer, the leading edge of the fan's blades should be higher as the fan spins counter-clockwise to cool occupants
with a wind-chill effect. On most models, the fan direction can be reversed with an electric switch located on the outside
of the metal housing, but the same effect can be achieved on other models by unscrewing and remounting the fan blades.
- An indoor fan is not designed for exterior use.
Ordinary indoor ceiling fans are unsafe to use outdoors or in humid environments, such as bathrooms. They will wear
out quickly. Fans that are rated “damp” are safe for humid environments, but they, too, should never be used where
they might come into contact with liquid water. Only fans that are rated “wet” are safe for such use, as they
incorporate features such as all-weather, UV-resistant blades, sealed motors, rust-resistant housing, and stainless steel
In summary, properly installed and maintained ceiling fans can inexpensively cool or warm building