Think of the compressor as a sort of "heart" of the system pumping the refrigerant though all the refrigeration components in a big loop. Refrigerant enters the compressor as a low pressure warm vapor and leaves it as a high pressure hot vapor. Condenser From the compressor, hot refrigerant vapor moves to the condenser. Here the high pressure hot refrigerant vapor is cooled by air blowing over finned condensing coils by the condenser fan as it moves through the finned coils. Using a fin comb helps keep these fins in shape. As the refrigerant "cools" it changes state from a hot vapor to a hot liquid at high pressure and moves onto the expansion valve. The compressor, condenser coil and condenser fan are all located in the big noisy boxy thing in your back yard often called a condensing unit Expansion ValveThe expansion valve is really what does the work. As the hot liquid refrigerant passes through a tiny opening at high pressure in the valve on one side, it emerges as a cool low pressure mist on the other side because as a gas expands, it cools. So now we have a low pressure cold liquid mist that moves onto the evaporator coil.Evaporator Coil The low pressure cold liquid leaving the expansion valve now runs through the evaporator coil located in the plenum of your furnace. Here the hot air of your home blows across the evaporator coil and heats it up while the cold coil cools off the air blowing across it and back into your home. As the refrigerant heats up, it boils and changes from a cold liquid and evaporates into a warm vapor. From there it moves back onto the compressor and exterior condensing unit and the cooling cycles continues. Maintenence Your air conditioning system needs to be maintained just like any other aspect of your home's HVAC system. See the tutorial Central Air Conditioning Unit and Heat Pump Maintenance for tips on how to maintaining your AC system. Designed to improve manufacturing process control in a printing plant, Carrier's invention controlled not only temperature but also humidity. Carrier used his knowledge of the heating of objects with steam and reversed the process. Instead of sending air through hot coils, he sent it through cold coils (filled with cold water). The air was cooled, and thereby the amount of moisture in the air could be controlled, which in turn made the humidity in the room controllable. The controlled temperature and humidity helped 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 as well. 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. Modern refrigerants have been developed to be more environmentally safe than many of the early chlorofluorocarbon-based refrigerants used in the early- and mid-twentieth century. These include as HCFCs (R-22, used in most U.S. homes even before 2011) and HFCs (R-134a, used in most cars) have replaced most CFC use. HCFCs, in turn, are supposed to have been in the process of being phased out under the Montreal Protocol and replaced by hydrofluorocarbons (HFCs) such as R-410A, which lack chlorine. HFCs, however, contribute to climate change problems. Moreover, policy and political influence by corporate executives resisted change. Corporations insisted that no alternatives to HFCs existed. The environmental organization Greenpeace solicited a European laboratory to research an alternative ozone- and climate-safe refrigerant in 1992, gained patent rights to a hydrocarbon mix of isopentane and isobutane, but then left the technology as open access. Their activist marketing first in Germany led to companies like Whirlpool, Bosch, and later LG and others to incorporate the technology throughout Europe, then Asia, although the corporate executives resisted in Latin America, so that it arrived in Argentina produced by a domestic firm in 2003, and then finally with giant Bosch's production in Brazil by 2004. In 1995, Germany made CFC refrigerators illegal. DuPont and other companies blocked the refrigerant in the U.S. with the U.S. E.P.A., disparaging the approach as "that German technology." Nevertheless, in 2004, Greenpeace worked with multinational corporations like Coca-Cola and Unilever, and later Pepsico and others, to create a corporate coalition called Refrigerants Naturally!. Then, four years later, Ben & Jerry's of Unilever and General Electric began to take steps to support production and use in the U.S. Only in 2011 did the E.P.A. finally decide in favor of the ozone- and climate-safe refrigerant for U.S. manufacture.
"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. However, 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. The use of CFC as a refrigerant was once common, being used in the refrigerants R-11 and R-12. In most countries the manufacture and use of CFCs has been banned or severely restricted due to concerns about ozone depletion. In light of these environmental concerns, beginning on November 14, 1994, the U.S. 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. R-744 is an effective refrigerant with a global warming potential of 1. It must use higher compression to produce an equivalent cooling effect.