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Air Conditioner

History

Main article: Air conditioning#History

In 1758, Benjamin Franklin and John Hadley, professor of chemistry at Cambridge University, conducted an experiment to explore the principle of evaporation as a means to rapidly cool an object. Franklin and Hadley confirmed that evaporation of highly volatile liquids such as alcohol and ether, could be used to drive down the temperature of an object past the freezing point of water. They conducted their experiment with the bulb of a mercury thermometer as their object and with a bellows used to "quicken" the evaporation; they lowered the temperature of the thermometer bulb down to 7 F (14 C) while the ambient temperature was 65 F (18 C). Franklin noted that soon after they passed the freezing point of water (32F) a thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about a quarter inch thick when they stopped the experiment upon reaching 7 F (14 C). Franklin concluded, "From this experiment, one may see the possibility of freezing a man to death on a warm summer's day".

In 1820, British scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air when the liquefied ammonia was allowed to evaporate. In 1842, Florida physician John Gorrie used compressor technology to create ice, which he used to cool air for his patients in his hospital in Apalachicola, Florida. He hoped eventually to use his ice-making machine to regulate the temperature of buildings. He even envisioned centralized air conditioning that could cool entire cities. Though his prototype leaked and performed irregularly, Gorrie was granted a patent in 1851 for his ice-making machine. His hopes for its success vanished soon afterward when his chief financial backer died; Gorrie did not get the money he needed to develop the machine. According to his biographer Vivian M. Sherlock, he blamed the "Ice King", Frederic Tudor, for his failure, suspecting that Tudor had launched a smear campaign against his invention. Dr. Gorrie died impoverished in 1855 and the idea of air conditioning faded away for 50 years.

Early commercial applications of air conditioning were manufactured to cool air for industrial processing rather than personal comfort. In 1902 the first modern electrical air conditioning was invented by Willis Haviland Carrier in Syracuse, NY. Designed to improve manufacturing process control in a printing plant, his invention controlled not only temperature but also humidity. The low heat and humidity were to help maintain consistent paper dimensions and ink alignment. Later Carrier's technology was applied to increase productivity in the workplace, and The Carrier Air Conditioning Company of America was formed to meet rising demand. Over time air conditioning came to be used to improve comfort in homes and automobiles. Residential sales expanded dramatically in the 1950s.

In 1906, Stuart W. Cramer of Charlotte, North Carolina, was exploring ways to add moisture to the air in his textile mill. Cramer coined the term "air conditioning", using it in a patent claim he filed that year as an analogue to "water conditioning", then a well-known process for making textiles easier to process. He combined moisture with ventilation to "condition" and change the air in the factories, controlling the humidity so necessary in textile plants. Willis Carrier adopted the term and incorporated it into the name of his company. This evaporation of water in air, to provide a cooling effect, is now known as evaporative cooling.

The first air conditioners and refrigerators employed toxic or flammable gases like ammonia, methyl chloride, and propane which could result in fatal accidents when they leaked. Thomas Midgley, Jr. created the first chlorofluorocarbon gas, Freon, in 1928. The refrigerant was much safer for humans but was later found to be harmful to the atmosphere's ozone layer. Freon is a trademark name of DuPont for any chlorofluorocarbon (CFC), hydrogenated CFC (HCFC), or hydrofluorocarbon (HFC) refrigerant, the name of each including a number indicating molecular composition (R-11, R-12, R-22, R-134A). The blend most used in direct-expansion home and building comfort cooling is an HCFC known as R-22. It is to be phased out for use in new equipment by 2010 and completely discontinued by 2020. R-12 was the most common blend used in automobiles in the United States until 1994 when most changed to R-134A. R-11 and R-12 are no longer manufactured in the United States, the only source for purchase being the cleaned and purified gas recovered from other air conditioner systems. Several non-ozone depleting refrigerants have been developed as alternatives, including R-410A, known by the brand name Puron. The most common ozone-depleting refrigerants are R-22, R-11, and R-123.

Innovation in air conditioning technologies continue, with much recent emphasis placed on energy efficiency and improving indoor air quality. As an alternative to conventional refrigerants, natural alternatives like CO2 (R-744) have been proposed.

Air conditioning applications

Main article: Air conditioning#Air conditioning applications

This section requires expansion.

Air conditioning system basics and theories

Refrigeration cycle

A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) evaporator coil, 4) compressor.

In the refrigeration cycle, a heat pump transfers heat from a lower-temperature heat source into a higher-temperature heat sink. Heat would naturally flow in the opposite direction. This is the most common type of air conditioning. A refrigerator works in much the same way, as it pumps the heat out of the interior and into the room in which it stands.

This cycle takes advantage of the way phase changes work, where latent heat is released at a constant temperature during a liquid/gas phase change, and where varying the pressure of a pure substance also varies its condensation/boiling point.

The most common refrigeration cycle uses an electric motor to drive a compressor. In an automobile, the compressor is driven by a belt over a pulley, the belt being driven by the engine's crankshaft (similar to the driving of the pulleys for the alternator, power steering, etc.). Whether in a car or building, both use electric fan motors for air circulation. Since evaporation occurs when heat is absorbed, and condensation occurs when heat is released, air conditioners use a compressor to cause pressure changes between two compartments, and actively condense and pump a refrigerant around. A refrigerant is pumped into the cooled compartment (the evaporator coil), where the low pressure causes the refrigerant to evaporate into a vapor, taking heat with it. In the other compartment (the condenser), the refrigerant vapor is compressed and forced through another heat exchange coil, condensing into a liquid, rejecting the heat previously absorbed from the cooled space.

Cylinder unloaders are a method of load control used mainly in commercial air conditioning systems. On a semi-hermetic (or open) compressor, the heads can be fitted with unloaders which remove a portion of the load from the compressor so that it can run better when full cooling is not needed. Unloaders can be electrical or mechanical.

Humidity

Air conditioning equipment usually reduces the humidity of the air processed by the system. The relatively cold (below the dew point) evaporator coil condenses water vapor from the processed air, much as a cold drink will condense water on the outside of a glass. The water is drained, removing water vapor from the cooled space and thereby lowering its relative humidity. Since humans perspire to provide natural cooling by the evaporation of perspiration from the skin, drier air (up to a point) improves the comfort provided. The comfort air conditioner is designed to create a 40% to 60% relative humidity in the occupied space. In food retail establishments, large, open chiller cabinets act as highly effective dehumidifiers.

Some air conditioning units dry the air without cooling it. These work like a normal air conditioner, except that a heat exchanger is placed between the intake and exhaust. In combination with convection fans, they achieve a similar level of comfort as an air cooler in humid tropical climates, but only consume about one-third the energy. They are also preferred by those who find the draft created by air coolers uncomfortable.

Refrigerants

Main article: Refrigerant

"Freon" is a trade name for a family of haloalkane refrigerants manufactured by DuPont and other companies. These refrigerants were commonly used due to their superior stability and safety properties. Unfortunately, evidence has accumulated that these chlorine-bearing refrigerants reach the upper atmosphere when they escape. Once the refrigerant reaches the stratosphere, UV radiation from the Sun cleaves the chlorine-carbon bond, yielding a chlorine radical. These chlorine atoms catalyze the breakdown of ozone into diatomic oxygen, depleting the ozone layer that shields the Earth's surface from strong UV radiation. Each chlorine radical remains active as a catalyst unless it binds with another chlorine radical, forming a stable molecule and breaking the chain reaction. CFC refrigerants is common, but decreasing usage include R-11 and R-12. In light of these environmental concerns, beginning on November 14, 1994, the Environmental Protection Agency has restricted the sale, possession and use of refrigerant to only licensed technicians, per Rules 608 and 609 of the EPA rules and regulations; failure to comply may result in criminal and civil sanctions. Newer and more environmentally-safe refrigerants such as HCFCs (R-22, used in most homes today) and HFCs (R-134a, used in most cars) have replaced most CFC use. HCFCs in turn are being phased out under the Montreal Protocol and replaced by hydrofluorocarbons (HFCs) such as R-410A, which lack chlorine. Carbon Dioxide (R-744) is being rapidly adopted as a refrigerant in Europe and Japan with Volkswagen being one of the first automotive manufacturers to roll out the new systems. R-744 must use higher compression to produce an equivalent cooling effect but has the advantage of being about 10% more efficient as compared to R-134A. R-744 also has a co2 factor of 1.

The external section of a typical single-room air conditioning unit. For ease of installation, these are frequently placed in a window. This one was installed through a hole cut in the wall.

The internal section of the above unit. The front panel swings down to reveal the controls.

Internal section of a modern Americool window air conditioner.

Reverse-cycle

This section requires expansion.

For more details on this topic, see Air conditioning#Heat pumps.

Types of air conditioner equipment

Window and through-wall units

Room air conditioners come in two forms: unitary and packaged terminal PTAC systems. Unitary systems, the common one room air conditioners, sit in a window or wall opening, with interior controls. Interior air is cooled as a fan blows it over the evaporator. On the exterior the air is heated as a second fan blows it over the condenser. In this process, heat is drawn from the room and discharged to the environment. A large house or building may have several such units, permitting each room be cooled separately. PTAC systems are also known as wall split air conditioning systems or ductless systems. These PTAC systems which are frequently used in hotels have two separate units (terminal packages), the evaportive unit on the exterior and the condensing unit on the interior, with tubing passing through the wall and connecting them. This minimizes the interior system footprint and allows each room to be adjusted independently. PTAC systems may be adapted to provide heating in cold weather, either directly by using an electric strip, gas or other heater, or by reversing the refrigerant flow to heat the interior and draw heat from the exterior air, converting the air conditioner into a heat pump. While room air conditioning provides maximum flexibility, when cooling many rooms it is generally more expensive than central air conditioning.

Evaporative coolers

Main article: Evaporative cooler

In very dry climates, evaporative coolers are popular for improving comfort during hot weather. This type of cooler is the dominant cooler used in Iran, which has the largest number of these units of any country in the world, causing some to referring to these units as "Persian coolers." An evaporative cooler is a device that draws outside air through a wet pad, such as a large sponge soaked with water. The sensible heat of the incoming air, as measured by a dry bulb thermometer, is reduced. The total heat (sensible heat plus latent heat) of the entering air is unchanged. Some of the sensible heat of the entering air is converted to latent heat by the evaporation of water in the wet cooler pads. If the entering air is dry enough, the results can be quite comfortable; evaporative coolers tend to feel as if they are not working during times of high humidity, when there is not much dry air with which the coolers can work to make the air as cool as possible for dwelling occupants. Unlike air conditioners, evaporative coolers rely on the outside air to be channeled through cooler pads that cool the air before it reaches the inside of a house through its air duct system; this cooled outside air must be allowed to push the warmer air within the house out through an exhaust opening such as a open door or window.

These coolers cost less and are mechanically simple to understand and maintain.

An early type of cooler, using ice for a further effect, was patented by John Gorrie of Apalachicola, Florida in 1842. He used the device to cool the patients in his malaria hospital.

Absorptive chillers

Main article: Absorption refrigerator

Portable air conditioners

Portable air conditioners (or PACs) are moveable units that can be used to cool a specific room in a home and do not require permanent installation. Warm air in the room is drawn in through inlets on the portable air conditioner. The air is circulated through the unit and is cooled by evaporator coils with refrigerant running through them and then blown out through the front. Remaining hot air in the unit is expelled and vented through the back with an exhaust hose. All portable air conditioners require exhaust hoses for venting.

Single Hosed Units

A single hosed unit has one hose that runs from the back of the portable air conditioner to the vent kit where hot air can be released. A single hosed portable air conditioner can cool a room that is 475 sq. ft. or smaller and has at most a cooling power of 12,000 BTUs.

Dual Hosed Units

Dual hosed units are typically used in larger rooms. One hose is used as the exhaust hose to vent hot air and the other as the intake hose to draw in additional air (usually from the outside). These units generally have a cooler power of 12,000-14,000 BTUs and cool rooms that are around 500 sq. ft. The reason an intake hose is needed to draw in extra air is because with higher BTU units, air is cycled in large amounts and hot air is expelled at a faster rate. This creates negative air pressure in the room, and the intake hose stabilizes the room's air pressure.

Split Units

Portable units are also available in split configuration, with the compressor and evaporator located in a separate external package and the two units connected via two detachable refrigerant pipes, as is the case with fixed split systems. Split portable units are superior to both single and dual hosed mono-portable units in that interior noise and size of the internal unit is greatly reduced due to the external location of the compressor, and no water needs to be drained from the internal unit due to the exterior location of the evaporator.

A drawback of split portable units compared with mono-portables is that a surface exterior to the building, such as a balcony must be provided for the external compressor unit to be located.

Unlike window ACs the split AC does not have an option of exchange of indoor and outdoor air.

Heat and Cool Units

Some portable air conditioner units are also able to provide heat by reversing the cooling process so that cool air is collected from a room and warm air is released. These units are not meant to replace actual heaters though and should not be used to cool rooms lower than 50 F (10 C).

Central air conditioning

Central air conditioning, commonly referred to as central air (U.S.) or air-con (UK), is an air conditioning system which uses ducts to distribute cooled and/or dehumidified air to more than one room, or uses pipes to distribute chilled water to heat exchangers in more than one room, and which is not plugged into a standard electrical outlet.

With a typical split system, the condenser and compressor are located in an outdoor unit; the evaporator is mounted in the air handler unit. With a package system, all components are located in a single outdoor unit that may be located on the ground or roof.

Central air conditioning performs like a regular air conditioner but has several added benefits:

When the air handling unit turns on, room air is drawn in from various parts of the building through return-air ducts. This air is pulled through a filter where airborne particles such as dust and lint are removed. Sophisticated filters may remove microscopic pollutants as well. The filtered air is routed to air supply ductwork that carries it back to rooms. Whenever the air conditioner is running, this cycle repeats continually.

Because the condenser unit (with its fan and the compressor) is located outside the home, it offers a lower level of indoor noise than a free-standing air conditioning unit.

Mini (Small) Duct, High Velocity

A central air conditioning system using high velocity air forced through small ducts (also called mini-ducts), typically round, flexible hoses about 2 inches in diameter. Using the principle of aspiration, the higher velocity air mixes more effectively with the room air, eliminating temperature discrepancies and drafts. A high velocity system can be louder than a conventional system if sound attenuators are not used, though they come standard on most, if not all, systems.

The smaller, flexible tubing used for a mini-duct system allows it to be more easily installed in historic buildings, and structures with solid walls, such as log homes. These small ducts are also typically longer contiguous pieces, and therefore less prone to leakage. Another added benefit of this type of ducting is the prevention of foreign particle buildup within the ducts, due to a combination of the higher velocity air, as well as the lack of hard corners.

Thermostats

Main article: Thermostat

Thermostats control the operation of HVAC systems, turning on the heating or cooling systems to bring the building to the set temperature. Typically the heating and cooling systems have separate control systems (even though they may share a thermostat) so that the temperature is only controlled "one-way." That is, in cold weather, a building that is too hot will not be cooled by the thermostat. Thermostats may also be incorporated into facility energy management systems in which the power utility customer may control the overall energy expenditure. In addition, a growing number of power utilities have made available a device which, when professionally installed, will control or limit the power to an HVAC system during peak use times in order to avoid necessitating the use of rolling blackouts. The customer is given a credit of some sort in exchange, so it is often to the advantage of the consumer to buy the most efficient[citation needed] thermostat possible.

Equipment capacity

Air conditioner equipment power in the U.S. is often described in terms of "tons of refrigeration." A "ton of refrigeration" is defined as the cooling power of one short ton (2000 pounds or 907 kilograms) of ice melting in a 24-hour period. This is equal to 12,000 BTU per hour, or 3517 watts. Residential central air systems are usually from 1 to 5 tons (3 to 20 kilowatts (kW)) in capacity.

The use of electric/compressive air conditioning puts a major demand on the electrical power grid in hot weather, when most units are operating under heavy load. In the aftermath of the 2003 North America blackout locals were asked to keep their air conditioning off. During peak demand, additional power plants must often be brought online, usually expensive peaker plants. A 1995 meta-analysis of various utility studies concluded that the average air conditioner wasted 40% of the input energy. This energy is lost in the form of heat, which must be pumped out. There is a huge opportunity to reduce the need for new power plants and to conserve energy.

In an automobile, the A/C system will use around 5 horsepower (4 kW) of the engine's power.[citation needed]

Seasonal Energy Efficiency Rating (SEER)

Main article: Seasonal Energy Efficiency Rating

For residential homes, some countries set minimum requirements for energy efficiency. In the United States, the efficiency of air conditioners is often (but not always) rated by the Seasonal Energy Efficiency Ratio (SEER). The higher the SEER rating, the more energy efficient is the air conditioner. The SEER rating is the BTU of cooling output during its normal annual usage divided by the total electric energy input in watt hours (Wh) during the same period.

SEER = BTU Wh

this can also be rewritten as:

SEER = (BTU / h) W, where "W" is the average electrical power in Watts, and (BTU/h) is the rated cooling power.

For example, a 5000 BTU/h air-conditioning unit, with a SEER of 10, would consume 5000/10 = 500 Watts of power on average (assuming 1000 hours of operation during a typical cooling season, i.e., 8 hours per day for 125 days per year)

The electrical energy consumed per year can be calculated as the average power multiplied by the annual operating time:

500 W 1000 h = 500,000 Wh = 500 kWh

Another method that yields the same result, is to calculate the total annual cooling output:

5000 BTU/h 1000 h = 5,000,000 BTU

Then, for a SEER of 10, the annual electrical energy usage would be:

5,000,000 BTU 10 = 500,000 Wh = 500 kWh

SEER is related to the coefficient of performance (COP) commonly used in thermodynamics and also to the Energy Efficiency Ratio (EER). The EER is the efficiency rating for the equipment at a particular pair of external and internal temperatures, while SEER is calculated over a whole range of external temperatures (i.e., the temperature distribution for the geographical location of the SEER test). SEER is unusual in that it is composed of an Imperial unit divided by an SI unit. The COP is a ratio with the same metric units of energy (joules) in both the numerator and denominator. They cancel out, leaving a dimensionless quantity. Formulas for the approximate conversion between SEER and EER or COP are available from the Pacific Gas and Electric Company:

(1)     SEER = EER 0.9

(2)     SEER = COP x 3.792

(3)     EER = COP x 3.413

From equation (2) above, a SEER of 13 is equivalent to a COP of 3.43, which means that 3.43 units of heat energy are pumped per unit of work energy.

Today, it is rare to see systems rated below SEER 9 in the United States, since older units are being replaced with higher-efficiency units. The United States now requires that residential systems manufactured in 2006 have a minimum SEER rating of 13 (although window-box systems are exempt from this law, so their SEER is still around 10). Substantial energy savings can be obtained from more efficient systems. For example by upgrading from SEER 9 to SEER 13, the power consumption is reduced by 30% (equal to 1 - 9/13). It is claimed that this can result in an energy savings valued at up to US$300 per year (depending on the usage rate and the cost of electricity). In many cases, the lifetime energy savings are likely to surpass the higher initial cost of a high-efficiency unit.

As an example, the annual cost of electric power consumed by a 72,000 BTU/h air conditioning unit operating for 1000 hours per year with a SEER rating of 10 and a power cost of $0.08 per kilowatt hour (kWh) may be calculated as follows:

unit size, BTU/h hours per year, h power cost, $/kWh (SEER, BTU/Wh 1000 W/kW)

(72,000 BTU/h) (1000 h) ($0.08/kWh) [(10 BTU/Wh) (1000 W/kW)] = $576.00 annual cost

A common misconception is that the SEER rating system also applies to heating systems. However, SEER ratings only apply to air conditioning.

Air conditioners (for cooling) and heat pumps (for heating) both work similarly in that heat is transferred or "pumped" from a cooler heat source to a warmer "heat sink". Air conditioners and heat pumps usually operate most effectively at temperatures around 10 to 13 degrees Celsius (C) (50 to 55 degrees Fahrenheit (F)). A balance point is reached when the heat source temperature falls below about 4 C (40 F), and the system is not able to pull any more heat from the heat source (this point varies from heat pump to heat pump). Similarly, when the heat sink temperature rises to about 49 C (120 F), the system will operate less effectively, and will not be able to "push" out any more heat. Geothermal heat pumps do not have this problem of reaching a balance point because they use the ground as a heat source/heat sink and the ground's thermal inertia prevents it from becoming too cold or too warm when moving heat from or to it. The ground's temperature does not vary nearly as much over a year as that of the air above it.

Insulation

This section requires expansion.

Insulation reduces the required power of the air conditioning system. Thick building walls, reflective roofing, curtains, and trees next to buildings also cut down on system and energy requirements.

Home air conditioning systems around the world

Domestic air conditioning is most prevalent and ubiquitous in developed Asian and Middle Eastern nations and territories, such as Japan, Taiwan, South Korea, Singapore, Hong Kong, Israel, China and the Persian Gulf States such as Bahrain, Kuwait, and the United Arab Emirates. This especially applies to Singapore and Hong Kong due to most of the population living in small high-rise flats. In these areas, with high summer temperatures and a high standard of living, air conditioning is considered a necessity and not a luxury. Japanese-made domestic air conditioners are usually window or split types, the latter being more modern and expensive. In Israel, virtually all residential systems are split types. Air conditioning is also increasing in popularity with the rising standard of living in tropical Asian nations such as Thailand, India, Pakistan, Malaysia, and the Philippines.

In the United States, home air conditioning is most prevalent in the South/Southwest and on the East Coast, areas in which it has reached the ubiquity it enjoys in East Asia.[citation needed] Central air systems are most common in the United States, and are virtually standard in all new dwellings in most states.[citation needed]

In Canada, home air conditioning is less common than in East Asia and the United States, but it still quite prevalent. This is especially true of the Great Lakes regions of southern Ontario and Quebec, where there are especially high humidity levels. While window and split units are common in these regions, central air systems are the most widespread in Western Canada. Virtually all Western Canadian homes are built with already-compatible central forced air natural gas heating systems, making installing a central air system very simple. In Central Canada separate room-based hydro powered heating is more common, leading to the higher cost of retrofitting a central air system. The majority of modern urban high-rise condominiums built in Canadian cities have air conditioning systems. It is also offered as a relatively low-cost option on most new built homes. While energy is comparatively very cheap in Canada, the large size of the average Canadian home and cold winters make heating and cooling one of the largest household expenses. Canadian summers are uncomfortably hot, but rarely reach the dangerous temperatures experienced in the United State or Asia. As such, many Canadians, especially in older homes, simply choose to forgo air conditioning in lieu of simple fans and evaporative coolers. Aside from the cost, air conditioning is often considered environmentally unfriendly, even though the majority of household energy in Canada comes from hydro and nuclear. There have been a number of advances in more "green" technologies, including geothermal cooling and a new Toronto system that cools a number of office towers using cold water from Lake Ontario.

In Europe, home air conditioning is generally less common in part due to higher energy costs and moderate summer temperatures, but these devices use lots of energy and are considered environmentally unfriendly.[who?] Southern European countries such as Greece, on the other hand, have seen a wide proliferation of home air-conditioning units in recent years. The lack of air conditioning in residences, residential care homes, and medical facilities was identified as a contributing factor to the estimated 35,000 deaths  mostly in Germany, France and Italy  left in the wake of the 2003 heat wave.

See also

Air filter

Dehumidifier

EcoCute

Energy

Energy conservation

Heat pump

Heating

HVAC

Hydronics

Inverter

Noise mitigation

Renewable energy

Refrigeration

Trigeneration

Whole house fan

References

^ Cooling by Evaporation (Letter to John Lining). Benjamin Franklin, London, June 17, 1758

^ History of Air Conditioning Source: Jones Jr., Malcolm. "Air Conditioning". Newsweek. Winter 1997 v130 n24-A p42(2). Retrieved 1 January 2007.

^ The current status in Air Conditioning  papers & presentations

^ EPA Rules & Regulations restricting refrigerant

^ Air Conditioning Explained, retrieved 19 May 2009

^ Dahlgren, Derek; Jewell, Amy; Li, Ruth; et al.. "History of Air Conditioning". Bucknell University. http://www.facstaff.bucknell.edu/mvigeant/therm_1/AC_final/bg.htm. Retrieved 2007-09-15. 

^ Shane Smith (2000). Greenhouse gardener's companion: growing food and flowers in your greenhouse or sunspace (2nd ed.). Fulcrum Publishing. p. 62. ISBN 9781555914509. http://books.google.com/books?id=Onv60-c6iEIC&pg=PA62&dq=evaporative-cooler+exhaust+open+door+window&lr;=&as_brr=3&ei=kv2MSqH7AZqIlQShoKymBw#v=onepage&q=evaporative-cooler exhaust open door window&f=false. 

^ "Portable Air Conditioner FAQs". PortableAirShop.com. http://www.portableairshop.com/Buyers+Guide:+PAC+FAQ/BUYERS_GUIDE_PAC_FAQ,default,pg.html. Retrieved 2009-07-20. 

^ a b c "Portable Air Conditioner Buyer's Guide". PortableAirShop.com. http://www.portableairshop.com/Buyers+Guide:+Introduction+to+PAC/BUYERS_GUIDE_PAC_OVERVIEW,default,pg.html. Retrieved 2009-07-20. 

^ a b "Cooling Capacity Calculator". PortableAirShop.com. http://www.portableairshop.com/Buyers+Guide:+Air:+PAC+BTU+Calculator/BUYERS_GUIDE_PAC_BTU_CALCULATOR,default,pg.html. Retrieved 2009-07-20. 

^

^

^ "NIST Guide to the SI". National Institute of Standards and Technology. http://physics.nist.gov/Pubs/SP811/appenB9.html. Retrieved 2007-05-18. 

^ "Energy Glossary - S". Energy Glossary. Energy Information Administration. http://www.eia.doe.gov/glossary/glossary_s.htm. Retrieved 2006-07-02. 

^ SEER conversion formulas from Pacific Gas and Electric

^ United States Department of Energy (2006-01-23). "Stronger Manufacturers' Energy Efficiency Standards for Residential Air Conditioners Go Into Effect Today". Press release. http://www.energy.gov/news/3097.htm. Retrieved 2006-07-02. 

^ " " (in Greek). news in.gr (Athens: Lambrakis Press). 2007-07-25. http://www.in.gr/news/article.asp?lngEntityID=819799&lngDtrID=244. Retrieved 2008-06-30. 

External links

Wikimedia Commons has media related to: Air conditioners

"DENSO Develops World's First CO2 Car Air Conditioner". The Auto Channel. 2002-12-04. http://www.theautochannel.com/news/2002/12/04/151245.html. Retrieved 2008-07-19. 

Space heating and cooling from the U.S. Department of Energy's Energy Efficiency and Renewable Energy

UK Enhanced Capital Allowance Scheme (ECA), a UK Government scheme to provide tax rebates for companies who use products which are ECA approved.

International Energy Agency - Energy Conservation In Buildings And Community Systems

Top-Rated Energy-Efficient Central Air Conditioners

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Viair 90P Portable Compressor Kit 00093 $78.95 Viair Portable Compressors in stock now! Read Viair 90P Portable Compressor Kit 00093 customer reviews. AutoAccessoriesGarage.com has the best selection of Viair Air Compressors at the lowest prices around. Viair 90P Portable Compressor Kit 00093 are chosen by auto enthusiasts everywhere to personalize their vehicles. Viair 90P Portable Compressor Kit available now at AutoAccessoriesGarage.

Viair 300 Series Portable Compressor Kit $149.95 Viair Portable Compressors in stock now! Read Viair 300 Series Portable Compressor Kit customer reviews. AutoAccessoriesGarage.com has the best selection of Viair Air Compressors at the lowest prices around. Viair 300 Series Portable Compressor Kit are chosen by auto enthusiasts everywhere to personalize their vehicles. Viair 300 Series Portable Compressor Kit available now at AutoAccessoriesGarage.

Viair 300P Portable Compressor Kit 30033 $149.95 Viair Portable Compressors in stock now! Read Viair 300P Portable Compressor Kit 30033 customer reviews. AutoAccessoriesGarage.com has the best selection of Viair Air Compressors at the lowest prices around. Viair 300P Portable Compressor Kit 30033 are chosen by auto enthusiasts everywhere to personalize their vehicles. Viair 300 Series Portable Compressor Kit available now at AutoAccessoriesGarage.

Viair 400P Portable Compressor Kit 40043 $198.95 Viair Portable Compressors in stock now! Read Viair 400P Portable Compressor Kit 40043 customer reviews. AutoAccessoriesGarage.com has the best selection of Viair Air Compressors at the lowest prices around. Viair 400P Portable Compressor Kit 40043 are chosen by auto enthusiasts everywhere to personalize their vehicles. Viair 400 Series Portable Compressor Kit available now at AutoAccessoriesGarage.

Viair 440P Portable Compressor Kit 44043 $288.95 Viair Portable Compressors in stock now! Read Viair 440P Portable Compressor Kit 44043 customer reviews. AutoAccessoriesGarage.com has the best selection of Viair Air Compressors at the lowest prices around. Viair 440P Portable Compressor Kit 44043 are chosen by auto enthusiasts everywhere to personalize their vehicles. Viair 400 Series Portable Compressor Kit available now at AutoAccessoriesGarage.

VIAIR 44043 Viair 440P Portable Air Compressor Kit $384.74 440P is the ultimate portable compressor kit. It can inflate a 37inch tire from 0 to 30 PSI in less than 5 minutes. The 440P is the largest and most powerful portable compressor kit available today. Rock crawlers and semitruckers alike will find the power of this unit irreplaceable. VIAIR 440P portable compressors are shipped complete with an openended (freeflowing) air delivery hose with a quickconnect coupling a pressure gauge an air filter element with replaceable air filtration media a vibrationresistant sand tray inflation tips and a deluxe carry bag for simple stowage and increased portability.

400PA Automatic Portable Air Compressor Kit by VIAIR for Jeep $259.99 12-volt;Duty cycle = 33% @ 100 psi;Max working pressure = 150 psi;Max amp draw = 26 amps;Dimensions = 11.25 in. L x 4 in. W x 7 in. H;Automatic shut-off function;Vibration-resistant diamond plate sand tray 400PA Automatic Portable Air Compressor Kit by VIAIR for Jeep

400PRV Automatic Portable Air Compressor Kit by VIAIR for Jeep $299.99 12-volt;Duty cycle = 33% @ 100 psi;Max working pressure = 150 psi;Max amp draw = 26 amps;Dimensions = 11.25 in. L x 4 in. W x 7 in. H;Automatic shut-off function;Vibration-resistant diamond plate sand tray;60 ft. reach;Tire inflation gun with 130 psi gaug 400PRV Automatic Portable Air Compressor Kit by VIAIR for Jeep

VIAIR 40045 Viair 400PA Automatic Portable Air Compressor Kit $337.94 400PAutomatic is VIAIR s first Automatic shutoff function portable compressor. This 33 duty cycle unit is capable of pressures up to 150 PSI and can be operated for up to 40 minutes at a time before needing to be rested. The 400PAutomatic comes with a closeended gas stationstyle air gun for added convenience. VIAIR 400P Automatic portable compressors are shipped complete with an air delivery hose with a quickconnect coupling a gas stationstyle air gun a pressure gauge an air filter element with replaceable air filtration media a vibrationresistant sand tray inflation tips and a deluxe carry bag for simple stowage and increased portability.

VIAIR 40043 Viair 400P Portable Compressor Kit $259.93 400P is a larger portable compressor kit that can inflate up to a 35inch tire from 0 to 30 PSI in less than 5 minutes. Used and approved of by off road enthusiasts worldwide the 400P can save you when you re miles from home. VIAIR 400P portable compressors are shipped complete with an openended (freeflowing) air delivery hose with a quickconnect coupling a pressure gauge an air filter element with replaceable air filtration media a vibrationresistant sand tray inflation tips and a deluxe carry bag for simple stowage and increased portability.

ViAir 450P-A Automatic Portable Compressor Kit 45043 $299.99 12-volt;Duty cycle = 100% @ 100 PSI;Max working pressure = 150 PSI;Max amp draw = 19 amps;Dimensions: 12.5" L x 6" W x 7.25" H;Automatic shut-off function;Vibration-resistant diamond plate sand tray;Dual battery clamps with 40-amp inline fuse holder;25 feet of air hose ViAir 450P-A Automatic Portable Compressor Kit 45043

T-Max Portable Air Compressor $147.21 T-Max Portable Compressors in stock now! Read T-Max Portable Air Compressor customer reviews. AutoAccessoriesGarage.com has the best selection of T-Max Air Compressors at the lowest prices around. T-Max Portable Air Compressor are chosen by auto enthusiasts everywhere to personalize their vehicles. T-Max Portable Air Compressor available now at AutoAccessoriesGarage.

VIAIR 44043 440P Portable Compressor Kit $384.74 VIAIR offers the most complete line of air compressors air accessories for both the onand offroad markets available anywhere. VIAIR compressors and components are used in the OEM segment 4x4 Sport Air Suspension and have become the industry standard for both 12 and 24volt automotive applications worldwide. VIAIR compressors are currently being used in every corner of the Globe even in the worlds harshest environments from arctic climates to the worlds harshest deserts from North America to Europe Africa Asia and even Australia. VIAIR is recognized by its customers and peers alike as the leading manufacturer of high performance air compressors for mobile pneumatic applications. Our goal is to consistently deliver performance reliability and value to our customers; providing the ultimate Vital Air Source the heart of any mobile pneumatic system to our valued partners worldwide. 440P is the ultimate portable compressor kit. It can inflate a 37inch tire from 0 to 30 PSI in less than 5 minutes. The 440P is the largest and most powerful portable compressor kit available today. Rock crawlers and semitruckers alike will find the power of this unit irreplaceable. VIAIR 440P portable compressors are shipped complete with an openended (freeflowing) air delivery hose with a quickconnect coupling a pressure gauge an air filter element with replaceable air filtration media a vibrationresistant sand tray inflation tips and a deluxe carry bag for simple stowage and increased portability.. Oilless Design. High Performance PTFE Piston Ring. Stainless Steel Valves. Moisture and Dust Resistant. Gearless DirectDrive Motor. Anodized Aluminum Alloy Cylinder. Automatic Reset Thermal Overload Protector. VibrationFree DiamondPlate Sand Tray. Deluxe Dual Compartment Carry Bag. 3pc. Inflation Tips Kit. 5in1 Inflator/Deflator with Inline 120 PSI Gauge. Dual Battery Clamps with 50amp Inline Fuse Holder.

Mabis Deluxe Combo NebXP Portable Handheld Compressor Nebulizer Kit, Each $119.99 Deluxe neb XP portable handheld compressor nebulizer kit. Extra performance, extra power source, extra portable. Output of up to 36 psi and 5 year warranty. Only 12.3 ounces. Includes handheld compressor nebulizer, clear cover, nebulizer, 7" air tubing, tubing connector, 5 air filters, AC adapter, rechargeable battery pack, DC auto adapter, standard battery pack and tote bag.

VIAR 00093 90P Portable Compressor Kit $103.93 90P is a small but powerful portable compressor kit that is capable of inflating up to 31inch tires by simply clamping the power leads to your battery connecting the tire chuck to the valve stem and turning the unit on. Tire pressure can be checked using the gauge mounted on top of the unit. Heavy duty steel stand with vibration isolators. Deluxe Carry Bag. 3Piece Inflation Tips Kit. Tire Chuck with Builtin Bleeder Valve. 120 PSI Gauge with Rubber Boot. Dual Battery Clamps. 30Amp Inline Fuse Holder. Power Cord: 12 / Air Hose: 3 . 12Volt. Permanent Magnetic Motor. Duty Cycle: 15 100 PSI. Max. Working Pressure: 120 PSI. Max. Amp Draw: 22 Amps.

Air Compressor Battery Clamp Kit $26.99 Air Compressor Battery Clamp Kit. Incl. 2 Heavy Duty Clamps. Necessary Hardware To connect To The Existing Compressor Cables.

VIAIR 00085 Viair 85P 12 Volt Portable Air Compressor Kit $78.25 85P is a small portable compressor with a builtin LED work light capable of inflating up to 31inch tires by simply plugging into your cigarette lighter power port (14.5 amps max.). Connect the screwon tire chuck to a tire valve stem before turning the unit on. Tire pressure can be monitored using the gauge incorporated into the top of the unit.

On Board Air Compressor Kit $546.99 On Board Air Compressor Kit; Double QuickShot; Side-to-side and Front-to-rear leaving; For (2) Air Springs; Dual Needle; Heavy duty compressor; 2 Gallon reserve tank; Easy-connect auxiliary air line makes adding air to tires and air toy a breeze

Measurement Limited MS5540 Trademark Tools Portable Air Compressor Kit with Light $43.81 Air Compressor with Light is a professional quality tool that makes checking your tire pressure a snap. Driving with correctly inflated tires is important for several reasons it increases safety reduces tread wear improves handling and ride performance and better fuel economy. Power required: DC 12V 10A. With light and pressure gauge. 10 foot cord with plug. 20 inch Air Hose. 2 Nozzle Adapter and Sports Needle. Size: 7.9 (L) x 4.0 (W) x 5.5 (H).

450PA Automatic Portable Air Compressor Kit by VIAIR $299.99 12-volt;Duty cycle = 100% @ 100 PSI;Max working pressure = 150 PSI;Max amp draw = 19 amps;Dimensions: 12.5 in. L x 6 in. W x 7.25 in. H;Automatic shut-off function;Vibration-resistant diamond plate sand tray;Dual battery clamps with 40-amp inline fuse hol

440P Portable Air Compressor Kit by VIAIR $295.99 12-volt;Duty cycle = 33% @ 100 PSI;Max working pressure = 150 PSI;Max amp draw = 38 amps;Dimensions = 13 in. L x 5.83 in. W x 6.69 in. H;Vibration-resistant diamond plate sand tray;5-in-1 Inflator/Deflator with inline 120 PSI gauge;Inflates 37 in. tires i

400PRV Automatic Portable Air Compressor Kit by VIAIR $299.99 12-volt;Duty cycle = 33% @ 100 PSI;Max working pressure = 150 PSI;Max amp draw = 26 amps;Dimensions = 11.25 in. L x 4 in. W x 7 in. H;Automatic shut-off function;Vibration-resistant diamond plate sand tray;60 ft. reach;Tire inflation gun with 130 PSI gaug

400PA Automatic Portable Air Compressor Kit by VIAIR $259.99 12-volt;Duty cycle = 33% @ 100 PSI;Max working pressure = 150 PSI;Max amp draw = 26 amps;Dimensions = 11.25 in. L x 4 in. W x 7 in. H;Automatic shut-off function;Vibration-resistant diamond plate sand tray

VIAIR 40043 400P Portable Compressor Kit $259.93 VIAIR offers the most complete line of air compressors air accessories for both the onand offroad markets available anywhere. VIAIR compressors and components are used in the OEM segment 4x4 Sport Air Suspension and have become the industry standard for both 12 and 24volt automotive applications worldwide. VIAIR compressors are currently being used in every corner of the Globe even in the worlds harshest environments from arctic climates to the worlds harshest deserts from North America to Europe Africa Asia and even Australia. VIAIR is recognized by its customers and peers alike as the leading manufacturer of high performance air compressors for mobile pneumatic applications. Our goal is to consistently deliver performance reliability and value to our customers; providing the ultimate Vital Air Source the heart of any mobile pneumatic system to our valued partners worldwide. 400P is a larger portable compressor kit that can inflate up to a 35inch tire from 0 to 30 PSI in less than 5 minutes. Used and approved of by off road enthusiasts. worldwide the 400P can save you when you're miles from home. VIAIR 400P portable compressors are shipped complete with an openended (freeflowing) air delivery hose with a quickconnect coupling a pressure gauge an air filter element with replaceable air filtration media a vibrationresistant sand tray inflation tips and a deluxe carry bag for simple stowage and increased portability.. Oilless Design. High Performance PTFE Piston Ring. Stainless Steel Valves. Moisture and Dust Resistant. Gearless Direct Drive Motor. Anodized Aluminum Alloy Cylinder. Automatic Reset Thermal Overload Protector. Aluminum Sand Tray with Vibration Isolators. Deluxe Dual Compartment Carry Bag. 3pc. Inflation Tips Kit. 5in1 Inflator/Deflator with Inline 100 PSI Gauge. Dual Battery Clamps with 40amp Inline Fuse Holder

VIAIR 30033 300P Portable Compressor Kit $194.93 VIAIR offers the most complete line of air compressors air accessories for both the onand offroad markets available anywhere. VIAIR compressors and components are used in the OEM segment 4x4 Sport Air Suspension and have become the industry standard for both 12 and 24volt automotive applications worldwide. VIAIR compressors are currently being used in every corner of the Globe even in the worlds harshest environments from arctic climates to the worlds harshest deserts from North America to Europe Africa Asia and even Australia. VIAIR is recognized by its customers and peers alike as the leading manufacturer of high performance air compressors for mobile pneumatic applications. Our goal is to consistently deliver performance reliability and value to our customers; providing the ultimate Vital Air Source the heart of any mobile pneumatic system to our valued partners worldwide. 300P is a larger portable compressor kit that is capable of inflating up to 33inch tires easily by simply clamping the power leads to your battery connecting the tire chuck to the valve stem and turning the unit on. Tire pressure can be monitored using the 5in1 Inflator/Deflator inline pressure gauge. VIAIR 300P portable compressors are shipped complete with an openended (freeflowing) air delivery hose with a quickconnect coupling a pressure gauge an air filter element with replaceable air filtration media a vibrationresistant sand tray inflation tips and a deluxe carry bag for simple stowage and increased portability.. Oilless Design. High Performance PTFE Piston Ring. Stainless Steel Valves. Moisture and Dust Resistant. Gearless Direct Drive Motor. Anodized Aluminum Alloy Cylinder. Automatic Reset Thermal Overload Protector. Aluminum Sand Tray with Vibration Isolators. Deluxe Dual Compartment Carry Bag. 3pc. Inflation Tips Kit. 5in1 Inflator/Deflator with Inline 100 PSI Gauge. Dual Battery Clamps with 40amp Inline Fuse Holder

Air Compressor Accessory Kit $32.99 Air Compressor Accessory Kit. Incl. 25 ft. Coiled Nylon Air Hose. Tire Inflator. Tire Pressure Gauge. Ball Inflator. Air Nozzle And Other Inflators/Adaptors And Fittings.