Air conditioning

While moving heat via machinery to provide air conditioning is a relatively modern invention, the cooling of buildings is not. The ancient Romans were known to circulate aqueduct water through the walls of certain houses to cool them. As this sort of water usage was expensive, generally only the wealthy could afford such a luxury.[2]
Air conditioning is one of those amenities that's easy to take for granted if you have it, and-on a hot, humid summer afternoon-easy to covet if you don't.[1]
Early commercial applications of air conditioning were manufactured to cool air for industrial processing rather than personal comfort.[2]

• While moving heat via machinery to provide air conditioning is a relatively modern invention, the cooling of buildings is not.(More...)
  
  

While moving heat via machinery to provide air conditioning is a relatively modern invention, the cooling of buildings is not. The ancient Romans were known to circulate aqueduct water through the walls of certain houses to cool them. As this sort of water usage was expensive, generally only the wealthy could afford such a luxury. [2] Air conditioning, including filtration, humidification, cooling, disinfection, etc., can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where an appropriate atmosphere is critical to patient safety and well-being.[2] Conversely with a dehumidifier, no energy is transfered out of the thermodynamic system (room) because the air conditioning unit (dehumidifier) is entirely inside the room. Therefore all of the electricity that is consumed by the dehumidifier is energy that is input into the thermodynamic system (the room), and remains in the room (as heat).[2] As a rule of thumb, 400 square feet (37m") can be cooled per 12,000 BTU/h (3.5kW or one ton of air conditioning) by a refrigerative air conditioner. Other factors will affect the total heat load.[2] The term air conditioning refers to the cooling and dehumidification of indoor air for thermal comfort.[2] Although nominally aimed at providing comfort for passengers and cooling of equipment, aircraft air conditioning presents a special process because of the low air pressure outside the aircraft.[2] In addition to buildings, air conditioning can be used for comfort in a wide variety of transportation including land vehicles, trains, ships, aircraft, and spacecraft.[2] Over time air conditioning came to be used to improve comfort in homes and automobiles.[2] Early commercial applications of air conditioning were manufactured to cool air for industrial processing rather than personal comfort.[2] In 747, Emperor Xuanzong (r. 712"762) of the Tang Dynasty (618"907) had the Cool Hall ( Liang Tian ) built in the imperial palace, which the Tang Yulin describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains.[2] Some more expensive window air conditioning units have the heat pump function.[2] In 1902 the first modern electrical air conditioning was invented by Willis Haviland Carrier. Designed to improve manufacturing process control in a printing plant, his invention controlled not only temperature but also humidity.[2] Modern air conditioning emerged from advances in chemistry during the 19th century, and the first large-scale electrical air conditioning was invented and used in 1902 by Willis Haviland Carrier.[2] During the subsequent Song Dynasty (960"1279), written sources mentioned the air conditioning rotary fan as even more widely used.[2] Without air conditioning, buildings must be built narrower or with light wells so that inner spaces receive sufficient outdoor air via natural ventilation.[2] Air conditioning also allows buildings to be taller since wind speed increases significantly with altitude making natural ventilation impractical for very tall buildings.[2]

The Australian Institute of Refrigeration Air Conditioning and Heating (AIRAH) was founded in 1920 and currently has around 10,000 members.[2] ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) is an organization devoted to the advancement of indoor-environment-control technology in the heating, ventilation, and air conditioning (HVAC) industry.[2] Innovation in air conditioning technologies continue, with much recent emphasis placed on energy efficiency and improving indoor air quality.[2] Air conditioning engineers broadly divide air conditioning applications into comfort and process.[2] Poorly operating air conditioning systems can generate sound levels that contribute to hearing loss, if exposures are endured over a long term. These levels are similar to the exposure of living near a busy highway or airport for a considerable length of time.[2]

Some air conditioning units dry the air without cooling it. They work like a normal air conditioner, except that a heat exchanger is placed between the intake and exhaust. In combination with convection fans they achieve a similar level of comfort as an air cooler in humid tropical climates, but only consume about 1/3 of the electricity. They are also preferred by those who find the draft created by air coolers uncomfortable.[3] SEER ratings only apply to air conditioning. Air conditioners (for cooling) and heat pumps (for heating) both work similarly in that heat is transferred or "pumped" from a cooler "heat-source" to a warmer " heat-sink ".[3]

A 1995 study of various utility studies of residential air conditioning concluded that the average air conditioner wasted 40% of the input energy. This energy is lost in the form of heat, which must be pumped out.[3] Central air conditioning, commonly referred to as central air (US) or air-con (UK), is an air conditioning system which uses ducts to distribute cooled and/or dehumidified air to more than one room, or uses pipes to distribute chilled water to heat exchangers in more than one room, and which is not plugged into a standard electrical outlet.[3] The controls are on the inside. A large house or building may have several such units. Should virtually every room be cooled with its own air conditioning unit, most of the day, it would be less expensive to use central air conditioning, though that may not be physically possible.[3]

Because the central air conditioning unit is located outside the home, it offers a lower level of noise indoors than a free-standing air conditioning unit.[3] In serious heat waves, air conditioning can save the lives of the elderly. Some local authorities even set up public cooling centers for the benefit of those without air conditioning at home.[3] The lack of air conditioning in homes, in residential care homes and in medical facilities was identified as a contributing factor to the estimated 35,000 deaths left in the wake of the 2003 heat wave.[3] In construction, a complete system of heating, ventilation, and air conditioning is referred to as HVAC. Its purpose, in the home or in the car, is to provide comfort during hot weather.[3] Air conditioning (including filtration, humidification, cooling, disinfection, etc.) can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where an appropriate atmosphere is critical to patient safety and well-being.[3] In Europe, home air conditioning is less common in part due to higher energy costs and more moderate summer temperatures.[3] In the United States, home air conditioning is more prevalent in the South and on the East Coast, in most parts of which it has reached the ubiquity it enjoys in East Asia.[3] The use of electric/compressive air conditioning puts a major demand on the nation's electrical power grid in warm weather, when most units are operating under heavy load. In the aftermath of the 2003 North America blackout locals were asked to keep their air conditioning off. During peak demand, additional power plants must often be brought online, usually natural gas fired plants because of their rapid startup.[3] The external section of a typical single-room air conditioning unit. For ease of installation, these are frequently placed in a window. This one was installed through a hole cut in the wall.[3] Heat would naturally flow in the opposite direction. This is the most common type of air conditioning.[3] Refrigeration air conditioning equipment usually reduces the humidity of the air processed by the system.[3] As with heating systems, the advantages of air conditioning generally far outweigh the disadvantages.[3]

When the temperature outside begins to climb, many people seek the cool comfort of indoor air conditioning. Like water towers water towers and power lines power lines, air conditioners are one of those things that we see every day but seldom pay much attention to.[4] The outside half of the equipment contains the compressor and condenser coil. Water cooled air conditioning systems: these work in a manner similar to the system listed above, but use water as a chiller to remove heat from the high temperature gas in the (usually but not always outside) compressor/condenser unit.[5] Tons of ice does not explain a key ingredient in the comfort produced by air conditioning systems, dehumidification of indoor air - that is, taking water out of the air.[5]

Rooftop combined units : While the list above describes the common components of a typical residential air conditioning system, other configurations and packaged units are also in increased use in both residential and commercial installations. Alternative designs may combine all components except for the duct work in a rooftop mounted unit such as the one shown above where it was mounted on a flat roof over offices at a commercial building.[5] Beyond comparing SEER ratings, a look at the building insulation, air leakage, and the layout, insulation, and adequacy of the air conditioning duct system are likely to have a very large, usually determining effect, on the operating cost of air conditioning systems in buildings.[5]

Traditional air conditioning units remain popular and include stand-alone units and central air central air.[6] There are several ways to check for and resolve problems associated with your central air conditioning.[6] We offer Free Heating and Cooling Price Quotes from local, prescreened air conditioning service experts.[6] Energy Efficient Air Conditioning In order to get the most out of your air conditioning system, it is important to understand the different designs, components, and operating principles.[6]

Air Conditioners Buying Guide What to look for in a central air conditioner, with handy air conditioning repair tips.[1] The air flow into and out of rooms must be carefully balanced to insure efficient operation of the system. These factors, as well how well a house is insulated, how it's used by your family, the climate and more must be taken into account when selecting and designing your system. That's why you should consult a qualified air conditioning contractor air conditioning contractor.[1] Air conditioning is one of those amenities that's easy to take for granted if you have it, and-on a hot, humid summer afternoon-easy to covet if you don't.[1]

We describe how to inspect residential air conditioning systems (A/C systems) to inform home buyers, owners, and home inspectors of common cooling system defects. The articles at this website describe the basic components of an air conditioning system and then we discuss how to estimate the rated cooling capacity of an air conditioning system by examining various data tags and components.[5] The cooling capacity of an air conditioning system is expressed in BTU's or tons.[5] The central air conditioning equipment is in questionable condition and may not be operable. As the equipment had clearly been shut down for a considerable time. we were not able to test-operate this equipment and we recommend that you make no attempt to turn it on before having it examined by a qualified air conditioning service person.[5] Air conditioning equipment age from serial number for the example above, the equipment was made after 1980. The first four digits of the serial number are week and year of manufacture, in this case, week 13 of 1989.[5] Serial number formats vary by range of years over which equipment was manufactured, and may vary among countries of manufacture for a given company's equipment, for example between the U.S. and Canada for Carrier air conditioning equipment.[5] Green links at left show where you are in our document & website. To continue reading this air conditioning inspection guide, use links to the document chapters at left or below. Links shown in green font indicate where you are in this document.[5] Our contact info is at inspect-ny.com/appointment.htm inspect-ny.com/appointment.htm. This website answers most questions about central air conditioning system troubleshooting, inspection, and repairs.[5] This website answers most questions about inspecting, troubleshooting, and repairing central air conditioning.[5] SEER stands for Seasonal Energy Efficiency Ratio. This is a measure of the energy efficiency of the air conditioning system.[5] Older air conditioning systems are likely to have a lower SEER (perhaps 5 or 6) than a newer more efficient system (perhaps SEER10).[5] The Air Conditioning Contractors of America (ACCA) The Air Conditioning Contractors of America opnbrktACCAclsbrkt online Contractor Locator Contractor Locator includes a special designation to identify contractors who sell and are knowledgeable about ENERGY STAR qualified HVAC equipment. ACCA is a non-profit association whose goal is to help the best Heating, Ventilation, Air-conditioning and Refrigeration (HVACR) contractors serve their customers.[7]

Section Contents:

• The Air-to-Air version, re-evaporates the water and discharges it through the ducted hose and can hence run continuously.(More...)
  
  

The Air-to-Air version, re-evaporates the water and discharges it through the ducted hose and can hence run continuously. A single duct unit draws air out of the room to cool its condenser. This air is then replaced by hot air from outside or other rooms, thus reducing efficiency. Modern units run on approximately 1 to 3 ratio i.e., to produce 3kW of cooling this will use 1kW of electricity. [2] A function of all cooling that use a compressor, is to create water as it cools the air.[2]

In a broader sense, the term can refer to any form of cooling, heating, ventilation or disinfection that modifies the condition of air.[2] The air next passes over the condensor coil re-warming the now dehumidified air. Note that the terms "condensor coil" and "evaporator coil" do not refer to the behavior of water in the air as it passes over each coil; instead they refer to the phases of the refrigeration cycle.[2] The outdoor condensor unit also switches roles to serve as the evaporator, and produces cold air (colder than the ambient outdoor air).[2] 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), sending the water to a drain and removing water vapor from the cooled space and lowering the relative humidity.[2]

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 open heart surgery require low temperatures (about 18 "C, 64 "F) and others such as neonatal relatively high temperatures (about 28 "C, 82 "F).[2] In both comfort and process applications the objective may be to not only control temperature, but also humidity, air quality, air motion, and air movement from space to space.[2] 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.[2]

Hose systems Air-to-Air and Monoblock are vented to the outside via air ducts.[2]

Dehumidifiers are commonly used in cold, damp climates to prevent mold growth indoors, especially in basements. They are also sometimes used in hot, humid climates for comfort because they reduce the humidity which causes discomfort (just as a regular air conditioner, but without cooling the room).[2] Heat pump is a term for a type of air conditioner in which the refrigeration cycle is able to be reversed, producing heat instead of cold in the indoor environment. Using an air conditioner in this way to produce heat is significantly more efficient than electric resistance heating.[2] Some home-owners elect to have a heat pump system installed, which is actually simply a central air conditioner with heat pump functionality (the refrigeration cycle is reversed in the winter).[2] As an example presume that inside the closed system a 100 watt light bulb is activated, and the air conditioner has an efficiency of 200%. The air conditioner's energy consumption will increase by 50 watts to compensate for this, thus making the 100W light bulb utilise a total of 150W of energy.[2] A regular air conditioner transfers energy out of the room by means of the condensor coil, which is outside the room (outdoors). This is a thermodynamic system where the room serves as the system and energy is transfered out of the system.[2] A specific type of air conditioner that is used only for dehumidifying is called a dehumidifier. A dehumidifier is different from a regular air conditioner in that both the evaporator and condensor coils are placed in the same air path, and the entire unit is placed in the environment that is intended to be conditioned (in this case dehumidified), rather than requiring the condensor coil to be outdoors.[2] Having the condensor coil in the main air path rather than in a separate, outdoor air path (as in a regular air conditioner) results in two consequenses-- the output air is warm rather than cold, and the unit is able to be placed anywhere in the environment to be conditioned, without a need to have the condensor outdoors.[2]

The evaporator (cold) coil is placed first in the air path, dehumidifying the air exactly as a regular air conditioner does.[2]

Air cooled portable air conditioners are compressor-based refrigerant system that uses air to exchange heat, similar to a car or typical household air conditioner. With this type of system the air is dehumidified as it is cooled.[2] Ironically, unlike a regular air conditioner, a dehumidifier will actually heat a room just as an electric heater that draws the same amount of electricity ( watts ) as the dehumidifier.[2]

A portable air conditioner or portable A/C is an air conditioner on wheels that can be easily transported inside a home or office. They are currently available with capacities of about 6,000 to 60,000 BTU/h (1,800 to 18,000 watts output) and with and without electric resistance heaters.[2]

Having the condensor coil in the same air path as the evaporator coil produces warm, dehumidified air.[2]

In very dry climates, evaporative coolers (or "swamp coolers") are popular for improving comfort during hot weather. This type of cooler is the dominant cooler used in Iran which has the largest number of units of any country in the world, hence some referring to them as Persian coolers. An evaporative cooler is a device that draws outside air through a wet pad, such as a large sponge soaked with water.[3] Some of the sensible heat of the entering air is converted to latent heat by the evaporation of water in the wet cooler pads.[3] The cold water is then run through radiators in air ducts for hydronic cooling. The dual use of the energy, both to generate electricity and cooling, makes this technology attractive when regional utility and fuel prices are right.[3] When the air handling unit turns on, room air is drawn in from various parts of the house through return-air ducts. This air is pulled through a filter where airborne particles such as dust and lint are removed.[3] With a typical split system, the condenser and compressor are located in an outdoor unit; the evaporator is mounted in the air handling unit (which is often a forced air furnace).[3] In an automobile, the compressor is driven by a belt over a pulley, the belt being driven by the engine's crankshaft (similar to the driving of the pulleys for the alternator, power steering, etc.). Whether in a car or the house, both use electric fan motors for air circulation.[3]

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.[3] The brine osmotically absorbs water vapor from the air. The second stage sprays water in the air, cooling the air by evaporation.[3] 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), sending the water to a drain and removing water vapor from the cooled space and lowering the relative humidity.[3]

The total heat ( sensible heat plus latent heat ) of the entering air is unchanged.[3] The sensible heat of the incoming air, as measured by a dry bulb thermometer, is reduced.[3] Many traditional air conditioners in homes or other buildings are single rectangular units used to cool an apartment, a house or part of it, or part of a building.[3]

In food retailing establishments large open chiller cabinets act as highly effective air dehumidifying units.[3] The ground's temperature does not vary nearly as much over a year as the air above it does.[3] Central air systems are most common in the United States, and are virtually standard in all new dwellings in most states.[3] Residential " central air " systems are usually from 1 to 5 tons (3 to 20 kW) in capacity.[3]

If the entering air is dry enough, the results can be quite comfortable. These coolers cost less and are mechanically simple to understand and maintain.[3] In one instance, a three-stage absorptive cooler first dehumidifies the air with a spray of salt-water or brine.[3]

Since evaporation occurs when heat is absorbed, and condensation occurs when heat is released, air conditioners are designed to use a compressor to cause pressure changes between two compartments, and actively condense and pump a refrigerant around.[3] An air conditioner is an appliance, system, or mechanism designed to extract heat from an area using a refrigeration cycle.[3]

The higher the SEER rating, the more energy efficient is the air conditioner. The SEER rating is the BTU of cooling output during its normal annual usage divided by the total electric energy input in watt-hours (W"h) during the same period.[3] Air conditioners and heat pumps usually operate most effectively at temperatures around 50 to 55 " F (10"13"C). A 'balance point' is reached when the heat source temperature falls below about 40" F (4"C), and the system is not able to pull any more heat from the heat-source. (This point varies from heat pump to heat pump).[3] Air conditioner equipment power in the U.S. is often described in terms of "tons of refrigeration".[3] The Association of Home Appliance Manufacturers ( AHAM ) offers a worksheet that can help you estimate how powerful an air conditioner you need.[3] The comfort air conditioner is designed to create a 40% to 60% relative humidity in the occupied space.[3] In the United States, the efficiency of air conditioners is often (but not always) rated by the Seasonal Energy Efficiency Ratio (SEER).[3]

Common problems include the compressor failing to turn on, the air not coming out cool enough, low airflow, and water leaks.[6] A new, energy-efficient home holds in air tighter than an old drafty house, which makes ventilation even more crucial.[6] Air moving through the house can increase the longevity of the building materials.[6] The house needs air exchanges to provide fresh, clean air for the family to breathe.[6] The first way involves a furnace that pulls the air it needs directly from the house. The second way includes a direct vent to the outside of the house.[6]

Air is required in houses for certain appliances to safely function as designed.[6]

Shopping For New A/C Units With today's advanced technology, selecting an air conditioner has become a complicated task, requiring much research and planning.[6] If you neglect to put time and energy into selecting the right air conditioner, you will soon pay for it when you begin to lose money due to a poor choice.[6]

Even though each of these machines has a pretty distinct look, they all work on the same principles. In this article, we will examine air conditioners -- from small to huge -- so you know more about what you're seeing.[4] For those who aren't familiar with the terms, a central air conditioner works from a central location to distribute conditioned air throughout a house. Unlike a small, window- or wall-mounted room air conditioner, designed to cool a small area, a central air conditioner borrows a central air handling unit such as a forced air furnace or heat pump and ductwork for whole-house delivery.[1] The related heat pump heat pump is essentially a central air conditioner that can be reversed in winter to heat a house.[1]

In relatively warm climates, central air conditioners have become more the norm than the exception. In addition to cooling, they dehumidify and filter air, making it more comfortable and cleaner.[1] Cooling capacity Manufacturers produce air conditioners in a variety of sizes, typically measured in "tons" or "BTUs per hour."[1]

One that is too large will cycle off and on too frequently, doing a poor job of dehumidifying the air, which degrades comfort. It's better to slightly undersize an air conditioner than to oversize it.[1] An air conditioner that is too small can't keep up with load requirements on a particularly hot day.[1]

When we cool the air, we in effect are squeezing the water molecules out of the air. When an air conditioner blows warm humid building air across an evaporator coil in the air handler unit, it is not only cooling the air, it's squeezing out some of the water in that air. Both of these effects, cooler air and drier air, increase the comfort for building occupants.[5] Air-cooled air conditioners (shown in the photo): this refers to the use of air to cool the compressor and the condenser coil used to return the refrigerant gas to a liquid state. These split systems usually have an inside evaporator cooling coil installed to work along with the blower and duct system which might also be sitting atop a heating furnace.[5] Manhole ventilation duct (liberated from New York City) was used along with a home made hood attached to the air conditioner to blow cool air into the home through a ceiling register.[5]

For the thermostat to call for cooling it must be in the "cool" position and the temperature set to a level below the ambient air temperature at the thermostat location.[5] COOLING SYSTEM INSPECTION LIMITATION: We check for normal temperature differential between input and output air, unusual operating noises, visible damage or defects, and a variety of other possible defects. This inspection is not technically exhaustive; a more thorough inspection, also not technically exhaustive, can be performed by a qualified HVAC service professional, and is recommended when any defects or malfunction are suspected.[5]

Cool air can hold less water (in the form of water molecules or gaseous form of H2O) than warm air.[5] Think of the warmer air as having more space between the gas molecules for the water molecules to remain suspended.[5]

Air handler circuit breaker: in the electric panel there will be a switch controlling power to the air handler/blower circuit, perhaps two different circuits, one for the air handler unit, and a second for the compressor/condenser unit.[5]

1. Air Conditioning / Air Conditioner Buying Guide by HomeTips
http://www.hometips.com/cs-protected/guides/aircond.html

2. Air conditioning - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Air_conditioning

3. Air conditioner - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Air_conditioner

4. Howstuffworks "How Air Conditioners Work"
http://home.howstuffworks.com/ac.htm

5. Central Air Conditioning Troubleshooting & Repair Guide: How to Inspect, Diagnose, & Repair Central Air Conditioning: Defects in A/C compressors, air handlers, duct work, and controls
http://www.inspect-ny.com/aircond/aircond1123.htm

6. Air Conditioning & Heating Systems - Free Price Quotes
http://www.hvackey.com/

7. Central Air Conditioners : ENERGY STAR
http://www.energystar.gov/index.cfm?c=cac.pr_central_ac