Innovative Mechanical, LLC
1700 Cumberland Point Dr Suite 17, Marietta
home goods store store general contractor
Sears Heating and Air Conditioning
Cumberland Mall, 2940 Cobb Pkwy, Atlanta
roofing contractor home goods store store
AirCom of Gorgia
3003 Greyfield Trace SE, Marietta
home goods store store point of interest
Assured Comfort Heating, Air, Plumbing
5590 Oakdale Rd SE #300, Mableton
plumber home goods store store
Aaron Services: Plumbing, Heating, Cooling, Septic
869 Pickens Industrial Dr N E #4, Marietta
plumber home goods store store
E. Smith Heating & Air Conditioning
964 Industrial Park Dr, Marietta
home goods store store general contractor
ARS / Rescue Rooter Atlanta (PL)
1775 W Oak Pkwy #800, Marietta
plumber home goods store store
Heating & Air Conditioning Inc
3483 Fairburn Pl NW, Atlanta
general contractor point of interest establishment
Coolray Heating & Air Conditioning
1787 Williams Dr, Marietta
home goods store store general contractor
24 Hour Air Service Inc
1401 Peachtree St NW #500, Atlanta
home goods store store general contractor
Sears Heating and Air Conditioning
400 Ernest W Barrett Pkwy NW, Kennesaw
roofing contractor home goods store store
Reliable Heating & Air, Plumbing and Electrical
1305 Chastain Rd NW Suite 500, Kennesaw
plumber electrician home goods store
1925 Cobblewood Dr, Kennesaw
home goods store store general contractor
inAir Heating & Air Conditioning
820 Acworth Due West Rd NW, Kennesaw
plumber home goods store store
Adkins Air Conditioning & Heating
3226 Douglas Ln, Kennesaw
general contractor point of interest establishment
Ful-Bro Heating and Air Conditioning, Inc.
3230 Cumberland Dr, Chamblee
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Stay Cool Heating & Cooling
1235 Hemingway Ln, Roswell
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Central Heating & Air Conditioning
2801, 3575 McCall Pl, Atlanta
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More About Air Conditioning Services from Wikipedia

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Air conditioning (often referred to as AC, A/C, or air con) is the process of removing heat and moisture from the interior of an occupied space, to improve the comfort of occupants. Air conditioning can be used in both domestic and commercial environments. This process is most commonly used to achieve a more comfortable interior environment, typically for humans and other animals; however, air conditioning is also used to cool/dehumidify rooms filled with heat-producing electronic devices, such as computer servers, power amplifiers, and even to display and store some delicate products, such as artwork.

Air conditioners often use a fan to distribute the conditioned air to an occupied space such as a building or a car to improve thermal comfort and indoor air quality. Electric refrigerant-based AC units range from small units that can cool a small bedroom, which can be carried by a single adult, to massive units installed on the roof of office towers that can cool an entire building. The cooling is typically achieved through a refrigeration cycle, but sometimes evaporative cooler or free cooling is used. Air conditioning systems can also be made based on desiccants (chemicals which remove moisture from the air) and subterraneous pipes that can distribute the heated refrigerant to the ground for cooling.

In the most general sense, air conditioning can refer to any form of technology that modifies the condition of air (heating, (de-) humidification, cooling, cleaning, ventilation, or air movement). In common usage, though, "air conditioning" refers to systems which cool air. In construction, a complete system of heating, Ventilation (architecture), and air conditioning is referred to as HVAC.

The 2nd-century Chinese mechanical engineer and inventor Ding Huan of the Han Dynasty invented a Fan (mechanical) for air conditioning, with seven wheels In 747, Emperor Xuanzong of Tang (r. 712–762) of the Tang Dynasty (618–907) had the ''Cool Hall'' (''Liang Dian'' ) built in the imperial palace, which the ''Tang Yulin'' describes as having hydraulics fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song Dynasty (960–1279), written sources mentioned the air conditioning rotary fan as even more widely used.

In 1758, Benjamin Franklin and John Hadley (chemist), a chemistry professor 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 speed up the evaporation. They lowered the temperature of the thermometer bulb down to

James Harrison (engineer)'s first mechanical ice-making machine began operation in 1851 on the banks of the Barwon River (Victoria) at Rocky Point in Geelong, Australia. His first commercial ice-making machine followed in 1853, and his patent for an ether vapor compression refrigeration system was granted in 1855. This novel system used a compressor to force the refrigeration gas to pass through a condenser, where it cooled down and liquefied. The liquefied gas then circulated through the refrigeration coils and vaporized again, cooling down the surrounding system. The machine produced

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 Carrier Corporation 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. Realizing that air conditioning would one day be a standard feature of private homes, particularly in regions with warmer climate, David St. Pierre DuBose (1898-1994) designed a network of ductwork and vents for his home ''Meadowmont'', all disguised behind intricate and attractive Georgian-style open moldings.

In 1945, Robert Sherman (engineer) of Lynn, Massachusetts invented a portable, in-window air conditioner that cooled, heated, humidified, dehumidified, and filtered the air.
The first air conditioners and refrigerators employed toxic or flammable gases, such as ammonia, methyl chloride, or propane, that could result in fatal accidents when they leaked. Thomas Midgley, Jr. created the first non-flammable, non-toxic chlorofluorocarbon gas, ''Freon'', in 1928. The name is a trademark name owned by DuPont for any chlorofluorocarbon (CFC), HCFC (HCFC), or hydrofluorocarbon (HFC) refrigerant. The refrigerant names include a number indicating the molecular composition (e.g., 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 chlorodifluoromethane (R-22).

Dichlorodifluoromethane (R-12) was the most common blend used in automobiles in the U.S. until 1994, when most designs changed to 1,1,1,2-Tetrafluoroethane due to the ozone-depleting potential of R-12. R-11 and R-12 are no longer manufactured in the U.S. for this type of application, but is still imported and can be purchased and used by certified HVAC technicians. For systems requiring only an occasional "shot" of R-12 and otherwise in good working order and performing far better than virtually all "R-134a" systems whether "converted" or "factory", even $50-$100 per pound of R-12 is considered "cheap" by many individuals.

Several non-ozone-depleting refrigerants have been developed as so-called alternatives, including R-410A. It was first commercially used by Carrier Corp. under the brand name ''Puron''. However, no "alternative" is a safe, effective, efficient and "legal" alternative and the use of so-called "alternatives" to top-off low R-12 systems has resulted in destroyed systems charged with mixed,incompatible and inseparable R-12 and "alternatives" that further cont meaminated, damaged or destroyed hundreds or thousands of dollars worth of systems, components, tools, recovery and recycling machines and tanks, charging and testing machines and gauges and tens to hundreds of pounds of recovered, recycled and reusable R-12 that ultimately had to be "illegally" released and dumped into the atmosphere and environment because "contaminated" R-12 is also considered hazardous waste and there is no legal means of transporting, recycling, separating or disposing of it.

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 HCFCs (Chlorodifluoromethane, as used in most U.S. homes before 2011) and hydrofluorocarbon (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 HFCs such as R-410A, which lack chlorine.

Air-conditioning systems are refrigeration systems for living and working spaces both stationary, such as homes and other inhabited structures, as well as mobile spaces such as cars, aircraft and construction equipment. And like all refrigeration systems, air-conditioners remove heat from that specific space and transfer it the exterior space the systems condenser unit is located in. In the process, the interior air as well as any "fresh" exterior air that is intentionally or incidentally allowed into the space is dehumidified and to an extent "filtered" as a result of the heat removal and dehumidification process.

Simply put, a refrigeration system works in much the same way human perspiration and a breeze transfer heat and humidity from inside our bodies to our environment, although in a closed loop. A refrigerant fluid confined in the closed loop is a chemical compound which has is more dense and has a higher specific heat capacity than atmospheric "air" above 32 degrees F at up to 99% relative humidity.

The closed loop typically contains anywhere from several ounces to several pounds of refrigerant and ideally no "air" or water vapor. With the system "off", depending on the refrigerant type, ambient environmental temperature and humidity around the exterior of the "loop" and the system's state of charge - i.e. how "full" it is, the static, uniform refrigerant pressure within the "loop" can vary from only 2-5 pounds per square inch at 32 degrees F for a mobile R-12 system to 30-40 psi at 80 degrees F for a similar system with R-134a to somewhere in between for a home system on a 50-degree day with R-22 refrigerant. By using the correct temperature/pressure chart,an accurate ambient temperature and quality, correctly-calibrated and accurate manifold gauges to check static system pressure, the system's state of charge
can be accurately and reliably determined. Both under-charged and over-charged systems will suffer reduced efficiency, decreased cooling, intermittent and inconsistent system operation and potential system mlfunctions or even catastrophic failure. Proper refrigerant type, lubricant type and "oil charge" are also crucial to system efficiency and like longevity.

In the refrigeratio system,the refrigerant serves essentially the same purpose as the coolant in a car's cooling system. While in the system's evaporator as a "cool" liquid, it absorbs heat from the air in a building or vehicle just as coolant absorbs heat while flowing through an engine. The refrigerant "compressor", which is like all "compressors" simply a positive-displacement pump for fluids such as gases or vapors, pumps refrigerant through the refrigeration system just as a water pump circulates coolant.

A temperature-controlled valve or fixed orifice in the system controls the flow rate of refrigerant through the system much the same way an engine's thermostat and/or water pump
bypass ensure that coolant flows to,through and from the water pump, engine and radiator only when and as quickly as necessary to absorb enough engine heat while in the
engine and release enough while in the radiator to sufficiently cool but not over-cool the engine while releasing enough to prevent rapid overheating if the engine suddenly heats up rapidly and/or the water pump and cooling fan slow down significantly.

In cooling systems the thermostat is "downstream" of the engine while the expanansion valve or orifice tube is "upstream" of the evaporator, but in a refrigeration system the refrigerant reaches the expansion valve or orifice tube and that restriction is what creates the "system pressure" by placing a major restriction in the flow of the refrigerant.

All pressure in hydraulic or pneumatic systems is the result of flow and restriction. Upstream of the restriction there is "high pressure" and the fluid is "hot" because the heat in the fluid is confined and concentrated in a smaller space and increased by "friction" from pumping and flow.

Because the fluid squeezing through the restriction can suddenly expand and flow freely with minimal restriction "downstream" of the
restriction that was causing most of the heat buildup, if there is a larger, empty low-presssure space downstream of the restriction, suddenly a little concentrated heat in the fluid has all kinds of "cold" space to fill, heat always moves toward "cold", the high-pressure, hot fluid suddenly becomes a very "cold", dense low-presssure liquid flowing slowly through a large,
cool space and it "refrigerates" that space and the container around it.

In a refrigeration system, that container is the evaporator and it's the tube/fin-type heat-exchanger in a freezer, refrigerator, vehicle dash assembly or furnace/AC unit which can reach temperatures down to or below 32 degrees F and over/through which a blower fan pumps "interior" air to remove heat from it by letting the evporator transfer it to the freezing cold refrigerant.

The unit is called an evaporator because as the refrigerant absorbs heat, that heat combined with the ever-lower system pressure downstream, where the compressor pumps refrigerant by creating an area of low pressure "upstream" of its inlet, and the reduced pressure lowers the boiling point of the liquid refrigerant just as increased pressures raise liquid boiling points, all combine to "evaporate" and boil the refrigerant as it passes through the evaporator.

While the evaporator transfers heat from the air and boils away the refrigerant, it condenses water vapor in the air on it's surface as long as its surface temp is lower than the dew point of the air. The condensate accumulates until there is enough to form droplets and run down the evaporator fins onto a tray or pan with one or more drain lines leading to an exterior drain. Typically a floor drain in a basement or evaporator drain in a vehicle. The puddle of water underneath a parked vehicle's firewall area in the summer after the AC has been operating for at least five or ten minutes and has normalized on a muggy, warm day is distilled water from the evaporator.

As long as the evaporator temperature is below the dew point of the air passing over it, condensation will continue to form although it takes a pretty significant drop to prevent it from evaporating again whenever a volume of "dry" air passes through again. Liquid water condensation on the evaporator insulates it and reduces its efficiency. When the system's evaporator icing prevention system or component doesn't function, has been bypassed or is incorrectly adjusted and the water freezes on the evaporator, the refrigerant temperature throughout the system becomes lower and lower, the evaporator becomes colder and colder and more and more condensation and ice form.

For a brief period of time it may be noticed the system is working "great" and is really "freezing out" the occupants of the building or vehicle. In reality it is freezing up and it's possible for the entire evaporator to turn into a literal block of ice that no air will flow through or around and that will thaw much more slowly than it froze up. Typically it will partially thaw and the system will begin cooling again only after a long period during which it will actually add heat and return humidity to the space so that when it begins briefly working again, it will freeze up sooner and usually harder and thicker than before.

Evaporator freezing can also damage the evaporator, expansion valve and even the compressor. Freeze-ups are to be avoided and the cause repaired immediately if serious expense and downtime later on is less desirable than relatively cheap and quick repair or even basic service and maintenance as soon as possible. A simply dirty evaporator or filter, a malfunctioning blower fan or plugged evaporator drain(s) can cause evaporator freezing.

After the refrigerant leaves the evaporator as a relatively cool, low-presssure gas having been boiled and expanded into a vapor, it is drawn into the suction side of the compressor. Compressing gases, contrary to popular belief, does not dramatically heat them. There may be a small amount of heat added by the gas acting as a "coolant" for compressor parts and to a very limited degree, but the compressor itself is primarily heated by the air it's pumping, and the pumping action and production of outlet flow invariably leading to downstream restriction concentrates, rather than creates, heat during the "compression" process.

In refrigeration systems, the final heat exchange and refrigerant state change in the refrigerant state occurs in the condenser. The compressor concentrates the heat in the refrigerant, pumps it - still in vapor/gas form - into the restriction of the condenser. As the exact opposite of the evaporator and a confined space into which a large volume of hot, low-presssure gas is pumped against and to what is ultimately the expansion valve or orifice tube, the condenser forces the refrigerant through a very long, narrow and slow series of passages in tubes made of a good heat conductor rather than a heat sink. As it travels through what amount's to the radiator for the refrigerant, its heat is released to the atmosphere, it cools and contracts and it leaves the condenser...condensed.

The condenser separates gas from liquid, organizes and directs and combines several small streams of cooler, denser and pure liquid refrigerant and serves as an attenuator and shock absorber for the pressure pulses of the compressor as well as an oil "strainer" so compressor oil doesn't circulate throughout the system and will be "pumped" back to the compressor when it shuts down.

And it supplies "fresh" refrigerant to the accumulator or receiver-drier where a cloth filter element and dessicant material filter the refrigerant and catch and hold any "water" that happens to end up in the system. Water and it's ever-present companion "air" combine to corrode, erode, damage and destroy expensive and invisible internal parts like compressor check valves, pistons and seals and can freeze and stick expansion valves as well. The filter and dessicant have extremely limited capacity to protect the system and are not a replacement for proper system service, repair, evacuation and charging.

Upon leaving the accumulator or receiver-drier as a high-pressure and relatively "cool" liquid headed for the expansion valve or orifice tube, the refrigerant enters the same vicious cycle all over again.

Evaporative cooling

In very dry climates, evaporative coolers, sometimes referred to as swamp coolers or desert coolers, are popular for improving coolness during hot weather. An evaporative cooler is a device that draws outside air through a wet pad, such as a large sponge (tool) soaked with water. The sensible heat of the incoming air, as measured by a Dry-bulb temperature, is reduced. The temperature of the incoming air is reduced, but it is also more humid, so the total heat (sensible heat plus latent heat) 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 substantial.

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 other types of 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 an open door or window.
Air conditioning can also be provided by a process called free cooling which uses pumps to circulate a coolant (typically water or a glycol mix) from a cold source, which in turn acts as a heat sink for the energy that is removed from the cooled space. Common storage media are deep aquifers or a natural underground rock mass accessed via a cluster of small-diameter boreholes, equipped with heat exchanger. Some systems with small storage capacity are hybrid systems, using free cooling early in the cooling season, and later employing a heat pump to chill the circulation coming from the storage. The heat pump is added because the temperature of the storage gradually increases during the cooling season, thereby declining its effectiveness.

Free cooling systems can have very high efficiencies, and are sometimes combined with seasonal thermal energy storage (STES) so the cold of winter can be used for summer air conditioning. Free cooling and hybrid systems are mature technology.
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 50% to 60% relative humidity in the occupied space.

Dehumidification and cooling

Refrigeration air conditioning equipment usually reduces the absolute humidity of the air processed by the system. The relatively cold (below the dewpoint) evaporator coil condenses water vapor from the processed air, much like an ice-cold drink will condense water on the outside of a glass. Therefore, water vapor is removed from the cooled air and the relative humidity in the room is lowered. The water is usually sent to a drain or may simply drip onto the ground outdoors.
The heat is ejected by the air conditioners condenser, which is located outside of the area being cooled.

Dehumidification program

Most modern air-conditioning systems feature a dehumidification cycle during which the compressor runs while the fan is slowed as much as possible
A specialized air conditioner that is used only for dehumidifying is called a dehumidifier. It also uses a refrigeration cycle, but differs from a standard air conditioner in that both the evaporator and the condenser are placed in the same air path. A standard air conditioner transfers heat energy out of the room because its condenser coil releases heat outside. However, since all components of the dehumidifier are in the ''same'' room, no heat energy is removed. Instead, the electric Watt consumed by the dehumidifier remains in the room as heat, so the room is actually ''heated'', just as by an electric heater that draws the same amount of power.

In addition, if water is condensed in the room, the amount of heat previously needed to evaporate that water also is re-released in the room (the Enthalpy of vaporization). The dehumidification process is the inverse of adding water to the room with an evaporative cooler, and instead releases heat. Therefore, an in-room dehumidifier always will warm the room and reduce the relative humidity indirectly, as well as reducing the humidity directly by condensing and removing water.

Inside the unit, the air passes over the evaporator coil first, and is cooled and dehumidified. The now dehumidified, cold air then passes over the condenser coil where it is warmed up again. Then the air is released back into the room. The unit produces warm, dehumidified air and can usually be placed freely in the environment (room) that is to be conditioned.

Dehumidifiers are commonly used in cold, damp climates to prevent mold growth indoors, especially in basements. They are also used to protect sensitive equipment from the adverse effects of excessive humidity in tropical countries.

Energy transfer

In a thermodynamically closed system, any power dissipated into the system that is being maintained at a set temperature (which is a standard mode of operation for modern air conditioners) requires that the rate of energy removal by the air conditioner increase. This increase has the effect that, for each unit of energy input into the system (say to power a light bulb in the closed system), the air conditioner removes that energy. To do so, the air conditioner must increase its power consumption by the inverse of its "efficiency" (coefficient of performance) times the amount of power dissipated into the system. As an example, assume that inside the closed system a 100 W heating element is activated, and the air conditioner has a coefficient of performance of 200%. The air conditioner's power consumption will increase by 50 W to compensate for this, thus making the 100 W heating element cost a total of 150 W of power.

It is typical for air conditioners to operate at "efficiencies" of significantly greater than 100%. However, it may be noted that the input electrical energy is of higher thermodynamic quality (lower entropy) than the output thermal energy (heat energy).

Air conditioner equipment power in the U.S. is often described in terms of "ton of refrigeration", with each approximately equal to the cooling power of one short ton (2000 pounds or 907 kilograms) of ice melting in a 24-hour period. The value is defined as 12,000 BTU per hour, or 3517 watts. Residential central air systems are usually from 1 to 5 tons (3.5 to 18 kW) in capacity.

Seasonal energy efficiency ratio

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 Kilowatt hour (W·h) during the same period.

: SEER = BTU ÷ (W·h)
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.

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 W·h = 500 kWh

Assuming 1000 hours of operation during a typical cooling season (i.e., 8 hours per day for 125 days per year).

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 W·h = 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 units divided by an SI unit. The COP is a ratio with the same metric units of energy (joules) in both the Fraction (mathematics) and Fraction (mathematics). They cancel out, leaving a dimensionless quantity. Formulas for the approximate conversion between SEER and EER or COP are available.[ SEER conversion formulas from Pacific Gas and Electric]. (2007-12-02). Retrieved on 2012-01-09.

: (1)     SEER = EER ÷ 0.9
: (2)     SEER = COP × 3.792
: (3)     EER = COP × 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.

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).

Installation types

Window unit and packaged terminal

Window unit air conditioners are installed in an open window. The interior air is cooled as a fan blows it over the evaporator. On the exterior the heat drawn from the interior is dissipated into the environment as a second fan blows outside air over the condenser. A large house or building may have several such units, allowing each room to be cooled separately.

In 1971, General Electric introduced a popular portable in-window air conditioner designed for convenience and portability.

Packaged terminal air conditioner systems are also known as wall-split air conditioning systems. They are ductless systems. PTACs, which are frequently used in hotels, have two separate units (terminal packages), the evaporative unit on the interior and the condensing unit on the exterior, with an opening 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 used to cool many rooms at a time it is generally more expensive than central air conditioning.

The first practical semi-portable air conditioning unit was invented by engineers at Chrysler Motors and offered for sale starting in 1935.

Split systems

Split-system air conditioners come in two forms: mini-split and central systems. In both types, the inside-environment (evaporative) heat exchanger is separated by some distance from the outside-environment (condensing unit) heat exchanger.

= Mini-split (ductless) system
A mini-split system typically supplies air conditioned and heated air to a single or a few rooms of a building. Multi-zone systems are a common application of ductless systems and allow up to 8 rooms (zones) to be conditioned from a single outdoor unit. Multi-zone systems typically offer a variety of indoor unit styles including wall-mounted, ceiling-mounted, ceiling recessed, and horizontal ducted. Mini-split systems typically produce per hour of cooling. Multi-zone systems provide extended cooling and heating capacity up to 60,000 Btu's.

Advantages of the ductless system include smaller size and flexibility for zoning or heating and cooling individual rooms. The inside wall space required is significantly reduced. Also, the compressor and heat exchanger can be located farther away from the inside space, rather than merely on the other side of the same unit as in a PTAC or window air conditioner. Flexible exterior hoses lead from the outside unit to the interior one(s); these are often enclosed with metal to look like common drainpipes from the roof. In addition, ductless systems offer higher efficiency, reaching above 30 SEER.

The primary disadvantage of ductless air conditioners is their cost. Such systems cost about US$1,500 to US$2,000 per ton (12,000 BTU per hour) of cooling capacity. This is about 30% more than central systems (not including ductwork) and may cost more than twice as much as window units of similar capacity."

An additional possible disadvantage is that the cost of installing mini splits can be higher than some systems. However, lower operating costs and rebate (marketing) or other financial incentives—offered in some areas—can help offset the initial expense.

=Central (ducted) air conditioning
Central (Duct (HVAC)) air conditioning offers whole-house or large-commercial-space cooling, and often offers moderate multi-zone temperature control capability by the addition of air-louver-control boxes.

In central air conditioning, the inside heat-exchanger is typically placed inside the central furnace/AC unit of the Forced-air central heating which is then used in the summer to distribute chilled air throughout a residence or commercial building.

The heat-exchanger cools the air that is being forced through it by the furnace blower. As the warm air comes in contact with this cool surface the water in the air condenses. By pulling the water molecules from the air. According to the psychometric chart is a conventional split system, which is divided into two parts (evaporator and condenser) and allows cooling or heating of several rooms with one external unit. In the outdoor unit of this air conditioner there is a more powerful compressor, ports for connecting several traces and automation with locking valves for regulating the volume of refrigerant supplied to the indoor units located in the room.

A large Multi Split System is called a Variable refrigerant flow system and can be used instead of a central air conditioner system, as it allows for higher energy efficiency but it is more expensive to purchase and install.

''Difference between split system and multi-split system'':

Other common types of air conditioning system are multi-split systems, the difference between separate split system and multi-split system in several indoor units. All of them are connected to the main external unit, but the principle of their operation is similar to a simple split-system.

Its unique feature is the presence of one main external unit that connected to several indoor units. Such systems might be the right solution for maintaining the microclimate in several offices, shops, large living spaces. Just few of outdoor units do not worsen the aesthetic appearance of the building.The main external unit can be connected to several different indoor types: floor, ceiling, cassette, etc.

Multi-split system installation considerations

Before selecting the installation location of air conditioner, several main factors need to be considered. First of all, the direction of air flow from the indoor units should not fall on the place of rest or work area. Secondly, there should not be any obstacles on the way of the airflow that might prevent it from covering the space of the premises as much as possible. The outdoor unit must also be located in an open space, otherwise the heat from the house will not be effectively discharged outside and the productivity of the entire system will drop sharply. It is highly advisable to install the air conditioner units in easily accessible places, for further maintenance during operation.

The main problem when installing a multi-split system is the laying of long refrigerant lines for connecting the external unit to the internal ones. While installing a separate split system, workers try to locate both units opposite to each other, where the length of the line is minimal. Installing a multi-split system creates more difficulties, since some of indoor units can be located far from the outside. The first models of multi-split systems had one common control system that did not allow you to set the air conditioning individually for each room. However, now the market has a wide selection of multi-split systems, in which the functional characteristics of indoor units operate separately from each other.

The selection of indoor units has one restriction: their total power should not exceed the capacity of the outdoor unit. In practice, however, it is very common to see a multi-split system with a total capacity of indoor units greater than the outdoor capacity by at least 20%. However, it is wrong to expect better performance when all indoor units are turned on at the same time, since the total capacity of the whole system is limited by the capacity of the outdoor unit. Simply put, the outdoor unit will distribute all its power to all operating indoor units in such a way that some of the rooms may not have a very comfortable temperature level. However, the calculation of the total power is not simple, since it takes into account not only the nominal power of the units, but also the cooling capacity, heating, dehumidification, humidification, venting, etc.

Portable units

A portable air conditioner can be easily transported inside a home or office. They are currently available with capacities of about and with or without electric-resistance heaters. Portable air conditioners are either evaporative or refrigerative.

The compressor-based refrigerant systems are air-cooled, meaning they use air to exchange heat, in the same way as a car radiator or typical household air conditioner does. Such a system dehumidifies the air as it cools it. It collects water condensed from the cooled air and produces hot air which must be vented outside the cooled area; doing so transfers heat from the air in the cooled area to the outside air.

= Portable split system
A portable system has an indoor unit on wheels connected to an outdoor unit via flexible pipes, similar to a permanently fixed installed unit.The portable units draw indoor air and expel it outdoors through a single duct. Many portable air conditioners come with heat as well as dehumidification function

= Portable hose system
Hose systems, which can be ''monoblock'' or ''air-to-air'', are vented to the outside via air Duct (HVAC). The ''monoblock'' type collects the water in a bucket or tray and stops when full. The ''air-to-air'' type re-evaporates the water and discharges it through the ducted hose and can run continuously.

A single-hose unit uses air from within the room to cool its condenser, and then vents it outside. This air is replaced by hot air from outside or other rooms (due to the negative pressure inside the room), thus reducing the unit's overall efficiency.

Modern units might have a coefficient of performance of approximately 3 (i.e., 1 kW of electricity will produce 3 kW of cooling). A dual-hose unit draws air to cool its condenser from outside instead of from inside the room, and thus is more effective than most single-hose units. These units create no negative pressure in the room.

= Portable evaporative system
Evaporative coolers, sometimes called "swamp coolers", do not have a compressor or condenser. Liquid water is evaporated on the cooling fins, releasing the vapor into the cooled area. Evaporating water absorbs a significant amount of heat, the Enthalpy of vaporization, cooling the air. Humans and animals use the same mechanism to cool themselves by Perspiration.

Evaporative coolers have the advantage of needing no hoses to vent heat outside the cooled area, making them truly portable. They are also very cheap to install and use less energy than refrigerative air conditioners.


Air-conditioning engineers broadly divide air conditioning applications into ''comfort'' and ''process'' applications.

Comfort applications

Comfort applications aim to provide a Building science that remains relatively constant despite changes in external weather conditions or in internal heat loads.

Air conditioning makes deep plan buildings feasible, for otherwise they would have to be built narrower or with light wells so that inner spaces received sufficient outdoor air via natural ventilation. Air conditioning also allows buildings to be taller, since Wind gradient increases significantly with altitude making natural ventilation impractical for very tall buildings.

Women have, on average, a significantly lower resting metabolic rate than men.{{Cite journal
|title=Energy consumption in buildings and female thermal demand
|date=3 August 2015

|first=Boris |last=Kingma
|first2=Wouter |last2=van Marken Lichtenbelt
Using inaccurate metabolic rate guidelines for air conditioning sizing can result in oversized and less efficient equipment, and setting system operating setpoints too cold can result in reduced worker productivity.

In addition to buildings, air conditioning can be used for many types of transportation, including automobiles, buses and other land vehicles, trains, ships, aircraft, and spacecraft.

= Domestic usage
Air conditioning is common in the US, with 88% of new single-family homes constructed in 2011 including air conditioning, ranging from 99% in the Southern United States to 62% in the Western United States. In Canada, air conditioning use varies by province. In 2013, 55% of Canadian households reported having an air conditioner, with high use in Manitoba (80%), Ontario (78%), Saskatchewan (67%), and Quebec (54%) and lower use in Prince Edward Island (23%), British Columbia (21%), and Newfoundland and Labrador (9%).

Process applications

Process applications aim to provide a suitable environment for a process being carried out, regardless of internal heat and humidity loads and external weather conditions. It is the needs of the process that determine conditions, not human preference. Process applications include these:

  • Chemistry and Biology laboratory

  • Cleanrooms for the production of integrated circuits, pharmaceuticals, and the like, in which very high levels of air cleanliness and control of temperature and humidity are required for the success of the process.

  • Data center environmental control of data centers

  • Facilities for breeding laboratory animals. Since many animals normally reproduce only in Spring (season), holding them in rooms in which conditions mirror those of spring all year can cause them to reproduce year-round.

  • Food cooking and food processing areas

  • Hospital operating theatres, in which air is filtered to high levels to reduce infection risk and the humidity controlled to limit patient dehydration. Although temperatures are often in the comfort range, some specialist procedures, such as Cardiac surgery, require low temperatures (about 18 °C, 64 °F) and others, such as neonatal, relatively high temperatures (about 28 °C, 82 °F).

  • Industrial ecology

  • Mining

  • Nuclear power facilities

  • Physical testing facilities

  • Plants and farm growing areas

  • Textile manufacturing

In both comfort and process applications, the objective may be to not only control temperature, but also humidity, air quality, and air movement from space to space.

Health effects

In hot weather, air conditioning can prevent heat stroke, dehydration from excessive sweating and other problems related to hyperthermia. Heat waves are the most lethal type of weather phenomenon in developed countries. Air conditioning (including filtration, humidification, cooling and disinfection) can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where proper atmosphere is critical to patient safety and well-being. It is sometimes recommended for home use by people with allergies.

Poorly maintained water cooling towers can promote the growth and spread of microorganisms, such as ''Legionella pneumophila'', the infectious agent responsible for Legionellosis, or thermophilic actinomycetes. As long as the cooling tower is kept clean (usually by means of a chlorine treatment), these health hazards can be avoided or reduced. Excessive air conditioning can have a negative effect on skin, causing it to dry out, and can also cause dehydration.

Environmental impacts

Power consumption and efficiency

Innovation in air conditioning technologies continues, with much recent emphasis placed on energy efficiency. Production of the electricity used to operate air conditioners has an environmental impact, including the release of greenhouse gases.

Cylinder unloaders are a method of load control used mainly in commercial air conditioning systems. On a semi-hermetic seal (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.

According to a 2015 government survey, 87% of the homes in the United States use air conditioning and 65% of those homes have central air conditioning. Most of the homes with central air conditioning have programmable thermostats, but approximately two-thirds of the homes with central air do not use this feature to make their homes more energy efficient. and allowing workers to wear more climate-appropriate clothing, such as polo shirts and Bermuda shorts. This approach has worked for the Cool Biz campaign in Japan.

  • Passive cooling techniques, such as:
    Natural ventilation under and through buildings
    Operating windows to induce a stack effect breeze
    Letting in cool air at night and closing windows during the day
    Operating shades to reduce solar gain
    Building slightly underground, to take advantage of unpowered conduction and geothermal mass
    Placement of trees, architectural shades, windows (and using window coatings) to reduce solar gain
    Thermal insulation placed to prevent heat from entering
    Light-colored building materials reflect away more incoming infrared radiation

  • Using a Fan (machine) if the air is below body temperature

  • Swamp coolers in hot but dry weather

  • Using a geothermal heat pump or ground-coupled heat exchanger

  • Using naturally cooler basement rooms more

  • Taking a siesta during the hottest part of the day

  • Sleeping outside on a porch or roof

  • Automobile power consumption

    In an automobile, the A/C system will use around 4 horsepower (3 kW) of the engine's power (physics), thus increasing fuel consumption of the vehicle.


    The selection of the working fluids (refrigerants) has a significant impact not only on the performance of the air conditioners but on the environment as well. Most refrigerants used for air conditioning contribute to global warming, and many also ozone depletion. CFCs, HCFCs, and HFCs are potent greenhouse gases when leaked to the atmosphere.

    The use of Chlorofluorocarbon as a refrigerant was once common, including the refrigerants R-11 and R-12 (sold under the brand name ''Freon-12''). Freon refrigerants were commonly used during the 20th century in air conditioners due to their superior stability and safety properties. When they are released accidentally or deliberately, these chlorine-bearing refrigerants eventually reach the Earth's atmosphere. Once the refrigerant reaches the stratosphere, ultraviolet from the Sun homolysis (chemistry) the chlorine-carbon Chemical bond, yielding a chlorine radical (chemistry). These chlorine radicals catalyst 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 until it binds with another radical, forming a stable molecule and quenching the chain reaction.

    Prior to 1994, most automotive air conditioning systems used R-12 as a refrigerant. It was replaced with R-134a refrigerant, which has no ozone depletion potential. Old R-12 systems can be retrofitted to R-134a by a complete flush and filter/dryer replacement to remove the mineral oil, which is not compatible with R-134a.

    Chlorodifluoromethane (also known as HCFC-22) has a global warming potential about 1,800 times higher than carbon dioxide. came into force in 2000 and banned the use of ozone depleting HCFC refrigerants such as R22 in new systems. The Regulation banned the use of R22 as a "top-up" fluid for maintenance between 2010 (for virgin fluid) and 2015 (for recycled fluid). This means that equipment that uses R22 can still operate, as long as it does not leak. Although R22 is now banned, units that use the refrigerant can still be serviced and maintained.

    The manufacture and use of CFCs has been banned or severely restricted due to concerns about ozone depletion (see also Montreal Protocol).[]

    As an alternative to conventional refrigerants, other gases, such as CO2 (R-744), have been proposed.

    In 1992, a non-governmental organization, Greenpeace, was spurred by corporate executive policies and requested that a European lab find substitute refrigerants. This led to two alternatives, one a blend of propane (R290) and isobutane (R600a), and one of pure isobutane. Industry resisted change in Europe until 1993, and in the U.S. until 2011, despite some supportive steps in 2004 and 2008 (see Refrigerant Development above).

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