Ceiling fan

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A modern ceiling fan The Black Beauty.jpg
A modern ceiling fan

A ceiling fan is a mechanical fan mounted on the ceiling of a room or space, usually electrically powered, suspended from the ceiling of a room, that uses hub-mounted rotating blades to circulate air.They cool people effectively by introducing slow movement into the otherwise still, hot air of a room. Fans do not reduce air temperature, unlike air-conditioning equipment but create a wind chill effect by eveporating sweat in the summer. In fact they heat up the air slightly due to the waste heat from the motor and friction between the moving air. Fans use significantly less power than air conditioning as cooling air is thermodynamically expensive. Conversely, a ceiling fan can also be used to reduce the stratification of warm air in a room by forcing it down to affect both occupants' sensations and thermostat readings, thereby improving climate control energy efficiency.

Contents

History

Punkah-type ceiling fans date back to 500 BC, and are native to India. Unlike modern rotary fans, these punkah fans move air by moving to and from, and were operated manually by cord. [1]

The first rotary ceiling fans appeared in the early 1860s and 1870s in the United States. At that time, they were not powered by any form of electric motor. Instead, a stream of running water was used, in conjunction with a turbine, to drive a system of belts which would turn the blades of two-blade fan units. These systems could accommodate several fan units, and so became popular in stores, restaurants, and offices. Some of these systems survive today, and can be seen in parts of the southern United States where they originally proved useful.

The electrically powered ceiling fan was invented in 1882 by Philip Diehl. He had engineered the electric motor used in the first electrically powered Singer sewing machines, and in 1882 he adapted that motor for use in a ceiling-mounted fan. Each fan had its own self-contained motor unit, with no need for belt drive. [2]

Almost immediately he faced fierce competition due to the commercial success of the ceiling fan. He continued to make improvements to his invention and created a light kit fitted to the ceiling fan to combine both functions in one unit. By World War I most ceiling fans were made with four blades instead of the original two, which made fans quieter and allowed them to circulate more air. The early turn-of-the-century companies who successfully commercialized the sale of ceiling fans in the United States were what is today known as the Hunter Fan Company, Robbins & Myers, Century Electric, Westinghouse Corporation and Emerson Electric.

By the 1920s, ceiling fans were commonplace in the United States, and had started to take hold internationally. From the Great Depression of the 1930s, until the introduction of electric air conditioning in the 1950s, ceiling fans slowly faded out of vogue in the U.S., [2] almost falling into total disuse in the U.S. by the 1960s; those that remained were considered items of nostalgia.

Late '80s Usha Prima, one of the most common ceiling fans in India Late 80s Usha Prima.jpg
Late '80s Usha Prima, one of the most common ceiling fans in India

Meanwhile, electric ceiling fans became very popular in other countries, particularly those with hot climates, such as India and the Middle East, where a lack of infrastructure and/or financial resources made energy-hungry and complex freon-based air conditioning equipment impractical. In 1973, Texas entrepreneur H. W. (Hub) Markwardt began importing highly efficient ceiling fans to the United States that were manufactured in India by Crompton Greaves, Ltd. Crompton Greaves had been manufacturing ceiling fans since 1937 through a joint venture formed by Greaves Cotton of India and Crompton Parkinson of England, and had perfected the world's most energy efficient ceiling fans thanks to its patented 20 pole induction motor with a highly efficient heat-dissipating cast aluminum rotor. These Indian manufactured ceiling fans caught on slowly at first, but Markwardt's Encon Industries branded ceiling fans (which stood for ENergy CONservation) eventually found great success during the energy crisis of the late 1970s and early 1980s, since they consumed far less energy (under 70 watts of electricity) than the antiquated shaded pole motors used in most other American made fans. The fans became very effective energy saving appliances for residential and commercial use by supplementing expensive air conditioning with a cooling wind-chill effect. Fans used for comfort create a wind chill by increasing the heat transfer coefficient, but do not lower temperatures directly.

Casablanca Fan Co. "Delta" ceiling fan from the early 1980s. Casablanca Delta ceiling fan.JPG
Casablanca Fan Co. "Delta" ceiling fan from the early 1980s.

Due to this renewed commercial success using ceiling fans effectively as an energy conservation application, many American manufacturers also started to produce, or significantly increase production of, ceiling fans. In addition to the imported Encon ceiling fans, the Casablanca Fan Company was founded in 1974. Other American manufacturers of the time included the Hunter Fan Co. (which was then a division of Robbins & Myers, Inc), FASCO (F. A. Smith Co.), and Emerson Electric; which was often branded as Sears-Roebuck.

Through the 1980s and 1990s, ceiling fans remained popular in the United States. Many small American importers, most of them rather short-lived, started importing ceiling fans. Throughout the 1980s, the balance of sales between American-made ceiling fans and those imported from manufacturers in India, Taiwan, Hong Kong and eventually China changed dramatically with imported fans taking the lion's share of the market by the late 1980s. Even the most basic U.S-made fans sold for $200 to $500, while the most expensive imported fans rarely exceeded $150.

Since 2000, important inroads have been made by companies such as Monte Carlo, Minka Aire, Quorum, Craftmade, Litex and Fanimation - offering higher price ceiling fans with more decorative value. In 2001, Washington Post writer Patricia Dane Rogers [3] wrote, “Like so many other mundane household objects, these old standbys are going high-style and high-tech.”

Uses

Unlike air conditioners, fans only move air—they do not directly change its temperature. Therefore, ceiling fans that have a mechanism for reversing the direction in which the blades push air (most commonly an electrical switch on the unit's switch housing, motor housing, or lower canopy) can help in both heating and cooling.

While ceiling fan manufacturers (mainly Emerson) have had electrically reversible motors in production since the 1930s, most fans made before the mid-1970s are either not reversible at all or mechanically reversible (have adjustable blade pitch) instead of an electrically reversible motor. In this case, the blades should be pitched to the right (or left if the motor spins clockwise) for downdraft, and to the opposite side for updraft. Hunter's "Adaptair" mechanism is perhaps the most well-known example of mechanical reversibility. In very rare cases, fans are both mechanically and electrically reversible, allowing for the fan to push air in either direction, while rotating either clockwise or counter-clockwise.

For cooling, the fan's direction of rotation should be set so that air is blown downward (Usually counter-clockwise from beneath). The blades should lead with the upturned edge as they spin. The breeze created by a ceiling fan creates a wind chill effect, speeding the evaporation of perspiration on human skin, which makes the body's natural cooling mechanism much more efficient. Since the fan works directly on the body, rather than by changing the temperature of the air, it is a waste of electricity to leave a ceiling fan on when no one is in a room unless air conditioning is in operation.[ citation needed ]

For heating, ceiling fans should usually be set to turn the opposite direction (usually clockwise; the blades should spin with the downward turned edge leading). Air naturally stratifies—that is, warmer air rises to the ceiling while cooler air sinks, meaning that colder air settles near the floor where people spend most of their time. A ceiling fan, with its direction of rotation set so that air is drawn upward, pulls the colder air off the floor, forcing the warmer air nearer the ceiling to move down to take its place, without blowing a stream of air directly at the occupants of the room. This action works to even out the temperature in the room, making it cooler nearer the ceiling, but warmer nearer the floor. Thus the thermostat in the area can be set a few degrees lower to save energy, while maintaining the same level of comfort.

The most commonplace use of ceiling fans today is in conjunction with an air conditioning unit. Without an operating ceiling fan, air conditioning units typically have both the tasks of cooling the air inside the room and circulating it. Provided the ceiling fan is properly sized for the room in which it is operating, its efficiency of moving air far exceeds that of an air conditioning unit, therefore, for peak efficiency, the air conditioner should be set to a low fan setting and the ceiling fan should be used to circulate the air.

Parts of a ceiling fan

The key components of a ceiling fan are the following:

Other components, which vary by model and style, can include:

Configurations

Operating a ceiling fan

A Hunter-branded "Eclipse", which is a basic modern ceiling fan with standard pull-chain controls for the fan motor and light kit Ceiling fan.png
A Hunter-branded "Eclipse", which is a basic modern ceiling fan with standard pull-chain controls for the fan motor and light kit

The way in which a fan is operated depends on its manufacturer, style, and the era in which it was made. Operating methods include:

Old-style choke and new-style capacitor based wall control Ceiling fan wall control types.jpg
Old-style choke and new-style capacitor based wall control

Types of ceiling fans

Many styles of ceiling fans have been developed over the years in response to several different factors such as growing energy-consumption consciousness and changes in decorating styles. The advent and evolution of electronic technology has also played a major role in ceiling fan development. Following is a list of major ceiling fan styles and their defining characteristics:

A cast-iron ceiling fan made by Hunter, dating from the early 1980s. This model is called the "Original". Hunter Original.jpg
A cast-iron ceiling fan made by Hunter, dating from the early 1980s. This model is called the "Original".
The Emerson "Heat Fan", one of the first fans to use a stack motor Emerson Universal.jpg
The Emerson "Heat Fan", one of the first fans to use a stack motor
A close-up of the dropped flywheel on a FASCO "Charleston" ceiling fan Fasco charleston flywheel.jpg
A close-up of the dropped flywheel on a FASCO "Charleston" ceiling fan
A spinner-motor fan Spinner fan.jpg
A spinner-motor fan
A dual-blade spinner fan from India A Dual blade Ceiling fan in India.JPG
A dual-blade spinner fan from India
Three fans driven by a single motor and belts Registrator output.png
Three fans driven by a single motor and belts
Orbit fans inside a train in Sri Lanka. Ventilateurs de train-Sri Lanka (2).jpg
Orbit fans inside a train in Sri Lanka.
A High-volume low-speed fan HVLS wood ceiling.jpg
A High-volume low-speed fan

Safety concerns with installation

A typical ceiling fan weighs between 8 and 50 pounds when fully assembled. While many junction boxes can support that weight while the fan is hanging still, a fan in operation exerts many additional stresses—notably torsion—on the object from which it is hung; this can cause an improper junction box to fail. For this reason, in the United States the National Electric Code (document NFPA 70, Article 314) states that ceiling fans must be supported by an electrical junction box listed for that use. It is a common mistake for homeowners to replace a light fixture with a ceiling fan without upgrading to a proper junction box.

Low-hanging fans/danger to limbs

Another concern with installing a ceiling fan relates to the height of the blades relative to the floor. Building codes throughout the United States prohibit residential ceiling fans from being mounted with the blades closer than seven feet from the floor;[ citation needed ] this sometimes proves, however, to not be high enough. If a ceiling fan is turned on and a person fully extends his or her arms into the air, as sometimes happens during normal tasks such as stretching or changing bedsheets, it is possible for the blades to strike their hands, potentially causing injury. Also, if one is carrying a long and awkward object, one end may inadvertently enter the path of rotation of a ceiling fan's blades, which can cause damage to the fan. Building codes throughout the United States also prohibit industrial ceiling fans from being mounted with the blades closer than 10 feet from the floor for these reasons.

MythBusters: "Killer Ceiling Fan"

In 2004, MythBusters tested the idea that a ceiling fan is capable of decapitation if an individual was to stick his or her neck into a running fan. Two versions of the myth were tested, with the first being the "jumping kid", involving a kid jumping up and down on a bed, jumping too high and entering the fan from below and the second being the "lover's leap", involving a husband dressed in a costume, leaping towards his wife in bed and entering the fan side-on. Kari Byron, Tory Belleci and Scottie Chapman took the lead on the investigation, though original MythBusters Jamie Hyneman and Adam Savage also assisted.

First, Kari and Scottie purchased a regular household fan and also an industrial fan, which has metal blades as opposed to wood and a more powerful motor. They and Tory then fashioned their human analogs - ballistic gel busts of Adam with actual human craniums, pig spines to approximate human spines, and latex arteries filled with fake blood - and then constructed rigs for both scenarios.

They busted the myth in both scenarios with both household and industrial fans, as tests proved that residential ceiling fans are, apparently by design, largely incapable of causing more than minor injury, having low-torque motors that stop quickly when blocked and blades composed of light materials that tend to break easily if impacted at speed (the household fan test of the "lover's leap" scenario actually broke the fan blades.) They did find that industrial fans, with their steel blades and higher speeds, proved capable of causing injury and laceration - building codes require industrial fans to be mounted with blades 10 feet above the floor, and the industrial fan test of the "lover's leap" scenario produced a lethal injury where the fan sliced through the jugular and into the vertebrae - but still lost energy rapidly once blocked and were unable to decapitate the test dummy. As a finale, Scottie, Tory and Kari created an even more dangerous fan with a lawn mower engine as the fan motor and razor sharp blades made from sheet metal in an attempt to duplicate the result, and even it was unable to achieve decapitation, but it caused lethal and horrifying injuries that compelled Adam to put it into the "MythBusters Hall of Fame." [7]

Wobble

Wobbling is usually caused by the weight of fan blades being out of balance with each other. This can happen due to a variety of factors, including blades being warped, blade irons being bent, blades or blade irons not being screwed on straight, or weight variation between blades. Also, if all the blades do not exert an equal force on the air (because they have different angles, for instance), the vertical reaction forces can cause wobbling. Wobble can also be caused by a motor flaw, but that very rarely occurs. Wobbling is not affected by the way in which the fan is mounted or the mounting surface.

Contrary to popular misconception, wobbling alone will not cause a ceiling fan to fall. [8] Ceiling fans are secured by clevis pins locked with either split pins or R-clips, so wobbling won't have an effect on the fan's security, unless of course, the pins/clips were not secured. To date, there are no reports of a fan wobbling itself off the ceiling and falling. However, a severe wobble can cause light fixture shades or covers to gradually loosen over time and potentially fall, posing a risk of injury to anyone under the fan, and also from any resulting broken glass. When the MythBusters were designing a fan with the goal of chopping off someone's head, Scottie used an edge finder to find the exact center of their blades with the aim of eliminating potentially very dangerous wobbling of their steel blades.

Wobbling may be reduced by measuring the tip of each blade from a fixed point on the ceiling (or floor) and ensuring each is equal. If the fan has a metal plate between the motor and blade, this may be gently adjusted by bending.

Related Research Articles

Turbine rotary mechanical device that extracts energy from a fluid flow

A turbine is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating electrical power when combined with a generator. A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are windmills and waterwheels.

Electric motor electromechanical device

An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force in the form of rotation of a shaft. Electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as a power grid, inverters or electrical generators. An electric generator is mechanically identical to an electric motor, but operates in the reverse direction, converting mechanical energy into electrical energy.

Starter (engine) electric motor used to start an internal combustion engine

A starter is a device used to rotate (crank) an internal-combustion engine so as to initiate the engine's operation under its own power. Starters can be electric, pneumatic, or hydraulic. In the case of very large engines, the starter can even be another internal-combustion engine.

Timer device that automatically times a process or event or activates an operation or another device at a preset time or times

A timer is a specialized type of clock used for measuring specific time intervals. Timers can be categorized into two main types. A timer which counts upwards from zero for measuring elapsed time is often called a stopwatch, while a device which counts down from a specified time interval is more usually called a timer. A simple example of this type is an hourglass. Working method timers have two main groups: Hardware and Software timers.

Brushless DC electric motor Synchronous electric motor powered by an inverter

A brushless DC electric motor, also known as electronically commutated motor and synchronous DC motors, are synchronous motors powered by direct current (DC) electricity via an inverter or switching power supply which produces electricity in the form of alternating current (AC) to drive each phase of the motor via a closed loop controller. The controller provides pulses of current to the motor windings that control the speed and torque of the motor.

DC motor motor that relies on magnet poles that repel and attract

A DC motor is any of a class of rotary electrical motors that converts direct current electrical energy into mechanical energy. The most common types rely on the forces produced by magnetic fields. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current in part of the motor.

A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives or electric roadway vehicle.

Punch press machine tool for punching

A punch press is a type of machine press used to cut holes in material. It can be small and manually operated and hold one simple die set, or be very large, CNC operated, with a multi-station turret and hold a much larger and complex die set.

Air handler air handler

An air handler, or air handling unit, is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system. An air handler is usually a large metal box containing a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to a ductwork ventilation system that distributes the conditioned air through the building and returns it to the AHU. Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served without ductwork

Adjustable-speed drive

Adjustable speed drive (ASD), also known as variable-speed drive (VSD), describes equipment used to control the speed of machinery. Many industrial processes such as assembly lines must operate at different speeds for different products. Where process conditions demand adjustment of flow from a pump or fan, varying the speed of the drive may save energy compared with other techniques for flow control.

Light fixture device that provides light

A light fixture, light fitting, or luminaire is an electrical device that contains an electric lamp that provides illumination. All light fixtures have a fixture body and one or more lamps. The lamps may be in sockets for easy replacement—or, in the case of some LED fixtures, hard-wired in place.

Fluid coupling

A fluid coupling or hydraulic coupling is a hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. It also has widespread application in marine and industrial machine drives, where variable speed operation and controlled start-up without shock loading of the power transmission system is essential.

Centrifugal fan mechanical fan that forces fluid to move at an angle (usually perpendicular) to the fan blades rotational axis

A centrifugal fan is a mechanical device for moving air or other gases in a direction at an angle to the incoming fluid. Centrifugal fans often contain a ducted housing to direct outgoing air in a specific direction or across a heat sink; such a fan is also called a blower fan, biscuit blower, or squirrel-cage fan. These fans increase the speed and volume of an air stream with the rotating impellers.

Fan (machine) machine with spinning blades used to create airflow

A fan is a powered machine used to create flow within a fluid, typically a gas such as air. A fan consists of a rotating arrangement of vanes or blades which act on the air. The rotating assembly of blades and hub is known as an impeller, rotor, or runner. Usually, it is contained within some form of housing or case. This may direct the airflow or increase safety by preventing objects from contacting the fan blades. Most fans are powered by electric motors, but other sources of power may be used, including hydraulic motors, handcranks, and internal combustion engines.

Industrial fans and blowers are machines whose primary function is to provide and accommodate a large flow of air or gas to various parts of a building or other structures. This is achieved by rotating a number of blades, connected to a hub and shaft, and driven by a motor or turbine. The flow rates of these mechanical fans range from approximately 200 cubic feet (5.7 m3) to 2,000,000 cubic feet (57,000 m3) per minute. A blower is another name for a fan that operates where the resistance to the flow is primarily on the downstream side of the fan.

In electrical engineering, electric machine is a general term for machines using electromagnetic forces, such as electric motors, electric generators, and others. They are electromechanical energy converters: an electric motor converts electricity to mechanical power while an electric generator converts mechanical power to electricity. The moving parts in a machine can be rotating or linear. Besides motors and generators, a third category often included is transformers, which although they do not have any moving parts are also energy converters, changing the voltage level of an alternating current.

A friction motor is a simple mechanism to propel toy cars, trucks, trains, action figures and similar toys. The motor consists of a large flywheel which is connected to the drive wheels of the toy via a very low gear ratio, so that the flywheel revolves faster. The flywheel's axis is perpendicular to the direction in which the toy faces and moves. When the toy is pushed forward, the drive wheels engage the flywheel. Pushing the vehicle forward repeatedly spins this flywheel up to speed. When let go, the flywheel drives the vehicle forward. The flywheel stores the kinetic energy of the initial acceleration and propels the toy after it is released.

Fan coil unit

A fan coil unit (FCU), also known as a Vertical Fan Coil-Unit (VFC), is a simple device consisting of a heating and/or cooling heat exchanger or 'coil' and fan. It is part of an HVAC system found in residential, commercial, and industrial buildings. A fan coil unit is a diverse device sometimes using ductwork, and is used to control the temperature in the space where it is installed, or serve multiple spaces. It is controlled either by a manual on/off switch or by a thermostat, which controls the throughput of water to the heat exchanger using a control valve and/or the fan speed.

Casablanca Fan Company is a ceiling fan company based in Industry, California. In the late 1970s, the company became known for their premium fans, which were marketed as furniture.

Alternator (automotive) machine

Alternators are used in modern automobiles to charge the battery and to power the electrical system when its engine is running.

References

  1. "Punkah. hand-operated hanging fan. a colonial legacy".
  2. 1 2 3 Scharff, Robert; Casablanca Fan Co. (1983). The Fan Book . Reston, VA: Reston Publishing. p.  128. ISBN   0-8359-1855-6.
  3. Dane Roger, Patricia (June 14, 2001). "Eye on Design". The Washington Post. p. H5.
  4. "Ceiling fan direction". LampsUSA. Retrieved April 4, 2018.
  5. "DC vs AC Ceiling Fans". www.hunterfan.co.uk. Retrieved May 25, 2015.
  6. Staff, S. L. A. "Best 7 Smart Ceiling Fans 2019: Google, Alexa and Wifi – smartlivingadvice.com" . Retrieved September 29, 2019.
  7. Savage, Adam (co-host); Hyneman, Jamie (co-host); Chapman, Scottie (Build Team); Belleci, Tory (Build Team); Byron, Kari (Build Team) (December 5, 2004). "Ming Dynasty Astronaut". MythBusters. Season 2. Episode 24. Begins at 25:45. Discovery.
  8. Gromicko, Nick. "Ceiling Fan Inspection". International Association of Certified Home Inspectors. Retrieved May 31, 2013.