AC Repair Brentwood
8335 Brentwood Blvd, Brentwood
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Sanact Heating & Cooling
Brentwood
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Sexton Heating and Air
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Perfect Climate
570 Valdry Ct # C9, Brentwood
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A Quality Heating & Air
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Tri Valley Air Systems
9010 Brentwood Blvd, Brentwood
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Blue Star Heating & Air
1409 Auto Center Dr, Antioch
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A Quality Heating & Air Inc
390 Carrol Ct # F, Brentwood
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California Mechanical Heating and Air Inc
3130 Balfour Road Suite D # 327, Brentwood
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Sunset Packing & Cooling
830 Sunset Rd, Brentwood
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A & L Services Heating & Air Conditioning
13626 Town Square Dr, Ventura
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Fairview Heating & Air Conditioning Inc.
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In & Out Air
31 Applegate Ln, Oakley
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Mendez Air
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AG Heating & Air Conditioning
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J and R Heating And Air Conditioning
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Central Heating & Air Conditioning
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Ambient Air Heating & Cooling
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Hvac Service Heating & Air Conditioning, Inc.
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Sears Heating and Air Conditioning
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roofing contractor home goods store store

More About Air Conditioning Services from Wikipedia


{{Redirect|A/C||AC (disambiguation)


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 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. This practice was replaced by mechanical ice-making machines.


The basic concept behind air conditioning is said to have been applied in ancient Egypt, where reeds were hung in windows and were moistened with trickling water. The evaporation of water cooled the air blowing through the window. This process also made the air more humid, which can be beneficial in a dry desert climate. In ancient Rome, water from aqueduct (watercourse) was circulated through the walls of certain houses to cool them. Other techniques in medieval Persia involved the use of cisterns and wind towers to cool buildings during the hot season.


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, so the only source for air-conditioning repair purposes is the cleaned and purified gas recovered from other air conditioner systems. Several non-ozone-depleting refrigerants have been developed as alternatives, including R-410A. It was first commercially used by Carrier Corp. under the brand name ''Puron''.


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.


In the refrigeration cycle, heat is transported from a colder location to a hotter area. As heat would naturally flow in the opposite direction, work is required to achieve this. A refrigerator is an example of such a system, as it transports the heat out of the interior and into its environment. The refrigerant is used as the medium which absorbs and removes heat from the space to be cooled and subsequently ejects that heat elsewhere.


Circulating refrigerant vapor enters the gas compressor, where its pressure and temperature are Gas compressor#Temperature. The hot, compressed refrigerant vapor is now at a temperature and pressure at which it can be Condensation and is routed through a Condenser (heat transfer). Here it is cooled by air flowing across the condenser coils and condensed into a liquid. Thus, the circulating refrigerant removes heat from the system and the heat is carried away by the air. The removal of this heat can be greatly augmented by pouring water over the condenser coils, making it much cooler when it hits the expansion valve.


The condensed, pressurized, and still usually somewhat hot liquid refrigerant is next routed through an Thermal expansion valve (often nothing more than a pinhole in the system's copper tubing) where it undergoes an abrupt reduction in pressure. That pressure reduction results in flash evaporation of a part of the liquid refrigerant, greatly lowering its temperature. The cold refrigerant is then routed through the evaporator coil. A fan blows the interior warm air (which is to be cooled) across the evaporator, causing the liquid part of the cold refrigerant mixture to evaporate as well, further lowering the temperature. The warm air is therefore cooled and is pumped by an exhaust fan/ blower into the room. To complete the refrigeration cycle, the refrigerant vapor is routed back into the compressor. In order for the process to have any efficiency, the cooling/evaporative portion of the system must be separated by some kind of physical barrier from the heating/condensing portion, and each portion must have its own fan to circulate its own "kind" of air (either the hot air or the cool air).


Modern air conditioning systems are not designed to draw air into the room from the outside, they only recirculate the increasingly cool air on the inside. Because this inside air always has some amount of moisture suspended in it, the cooling portion of the process always causes ambient warm water vapor to condense on the cooling coils and to drip from them down onto a catch tray at the bottom of the unit from which it must then be routed outside, usually through a drain hole. As this moisture has no dissolved minerals in it, it will not cause mineral buildup on the coils. This will happen even if the ambient humidity level is low. If ice begins to form on the evaporative fins, it will reduce circulation efficiency and cause the development of more ice, etc. A clean and strong circulatory fan can help prevent this, as will raising the target cool temperature of the unit's thermostat to a point that the compressor is allowed to turn off occasionally. A failing thermistor may also cause this problem. Refrigerators without a defrost cycle may have this same issue. Dust can also cause the fins to begin blocking air flow with the same undesirable result: ice.


By running an air conditioner's compressor in the opposite direction, the overall effect can be completely reversed and the indoor area will become heated instead of cooled (see heat pump). The engineering of physical and thermodynamic properties of gas–vapor mixtures is called psychrometrics.


= Heat pump unit
=
A heat pump is an air conditioner in which the refrigeration cycle can be reversed, producing heating instead of cooling in the indoor environment. They are also commonly referred to as a "reverse cycle air conditioner". The heat pump is significantly more energy efficient than electric resistance heating. Some homeowners elect to have a heat pump system installed as a feature of a central air conditioner. When the heat pump is in heating mode, the indoor evaporator coil switches roles and becomes the condenser coil, producing heat. The outdoor condenser unit also switches roles to serve as the evaporator, and discharges cold air (colder than the ambient outdoor air).


Air-source heat pumps are more popular in milder winter climates where the temperature is frequently in the range of 4–13 °C (40–55 °F), because heat pumps become inefficient in more extreme cold. This is because ice forms on the outdoor unit's heat exchanger coil, which blocks air flow over the coil. To compensate for this, the heat pump system must temporarily switch back into the regular air conditioning mode to switch the outdoor evaporator coil ''back'' to being the condenser coil, so that it can heat up and defrost. A heat pump system will therefore have a form of electric resistance heating in the indoor air path that is activated only in this mode in order to compensate for the temporary indoor air cooling, which would otherwise be uncomfortable in the winter.


The icing problem becomes much more severe with lower outdoor temperatures, so heat pumps are commonly installed in tandem with a more conventional form of heating, such as a natural gas or heating oil furnace, which is used instead of the heat pump during harsher winter temperatures. In this case, the heat pump is used efficiently during the milder temperatures, and the system is switched to the conventional heat source when the outdoor temperature is lower.


Absorption refrigerator are a kind of air-source heat pump, but they do not depend on electricity to power them. Instead, gas, solar power, or heated water is used as a main power source. An absorption pump dissolves ammonia gas in water, which gives off heat. Next, the water and ammonia mixture is depressurized to induce boiling, and the ammonia is boiled off, which absorbs heat from the outdoor air.
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 rejected by the condenser which is located outside of room to be 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.[https://web.archive.org/web/20071202130510/http://www.pge.com/docs/pdfs/biz/rebates/spc_contracts/2004_manuals_forms/spc_cooling_units.pdf SEER conversion formulas from Pacific Gas and Electric]. Web.archive.org (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.


''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.


= 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.


Uses


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

|volume=5
|issue=12
|pages=1054
|first=Boris |last=Kingma
|first2=Wouter |last2=van Marken Lichtenbelt
|doi=10.1038/NCLIMATE2741
|url=http://www.nature.com/articles/nclimate2741.epdf?referrer_access_token=wiK8dZ7RjiyB3YY0wnE8KtRgN0jAjWel9jnR3ZoTv0OxYB2QX8K1vS0r2SpOOxl5-QKWpBFSROwh6pmh1aKkmK1QsLkiUh-x9WiiZOVT_KZEM-75l-GmRqWTuSWcVzsluWpVahvIbv3gTKpiFDHPmMex7qU08kj3MLBk6q_QlXQ%3D&tracking_referrer=www.bbc.co.uk
}}
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.


    Refrigerants

    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).[https://www.sciencedaily.com/releases/2003/07/030730080139.htm Sciencedaily.com]


    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).


    Learn more about Air Conditioning Services:

    https://en.wikipedia.org/wiki/Air Conditioning