How Does an Air Conditioner Work?

air conditioner work
If you're getting central air installed for the first time, you may be curious about what each component does to help deliver climate-controlled air. As you take a closer look at your AC unit, it can help to know what is going on under the hood to make your air conditioner work. This guide will dive into the history of air conditioning, including when AC was invented. Next, we'll provide an overview of how your air conditioner works and answer some of your most-asked questions. Air Conditioning Goes Back as Early as 1748

Air Conditioner History

The beginnings of modern air conditioning goes back to 1748. That year, William Cullen, a professor at the University of Glasgow, discovered a way to evaporate liquids in a vacuum and invented refrigeration technology. It would be a century before Cullen's discoveries were put to use in air comfort. In the 1840s, Florida doctor John Gorrie was searching for a way to cool down patients affected by tropical fevers. He modified a steam engine to cool air. Gorrie's "ice machine" technology never took off due to public skepticism. And, a healthy amount of lobbying from the ice industry. In 1902, an engineer from the Buffalo Forge Company, Willis Carrier, designed a primitive electric air conditioning unit. It came to be after the Sackett-Wilhelms Lithographing and Publishing Company tasked him with solving a humidity problem that caused magazine pages to wrinkle during printing. Carrier's solution was an "Apparatus for Treating Air," which used cooling coils to control humidity. Carrier's technology took off after he broke with Buffalo Forge to form Carrier Engineering Corporation. He then improved his design in 1922 with the centrifugal refrigeration compressor. Many manufacturing companies, who knew the adverse effects of weather on production, began adopting the technology. The general public discovered the cool comfort of air conditioner work when 1920s nickelodeons began installing AC. Air conditioners became available for home use in 1947, and their popularity has soared ever since. In 2016, the most recent data available, 90% of U.S. households have air conditioning in some form. How Does an Air Conditioner Work?

How Does an Air Conditioner Work?

Air conditioning works thanks to four fundamental components:
  • Evaporator coil
  • Compressor
  • Condenser
  • Expansion valve
Each part plays a central role in cooling the air that circulates your home. This central air conditioning system diagram demonstrates how each of these components relates to the others. While we often think of this process in terms of central air, these same four parts are found in both split and self-contained air conditioning systems.

Step 1: Evaporator Coil Absorption

A common misconception about air conditioner work is that it creates cold air. In reality, the machine functions to cool the hot air already in your home. The evaporator coil is the part of the air conditioner that does this. You probably won't be able to see an evaporator coil on your air conditioning unit because it is usually kept inside a metal case in your attic or basement. The evaporator coil is often an A-shaped structure filled with many copper coils. Those coils come into direct contact with the air inside your home via your ductwork. First, warm air is drawn into the system through a vent. A fan blows this air over an evaporator coil, which is cold. This process cools down the inlet air. Once it has been cooled, it will travel back into your house through the ducts. It will be pulled in again and again until it reaches the temperature you set for your home.

Step 2: Refrigerant Temperature Alteration

The evaporator coil is cold because it is filled with a refrigerant, also known as a heat transfer fluid. As the warm air passes over these coils, the refrigerant absorbs the heat, leaving the air cool. The cooling process causes moisture within the incoming air to condense and form water droplets. During this process, the coolant also absorbs this moisture. The refrigerant makes the air both cool and dry, thus dehumidifying your home. As the refrigerant heats up, it vaporizes, turning from a liquid to a gas. To keep from overheating and continue the process of cooling air, the AC unit needs to discharge the heat from the hot, vaporized coolant. It does so by traveling to a compressor. If you have a centralized AC unit, the compressor will be outside of your home. The compressor pressurizes this refrigerant in its gaseous state by physically reducing the volume the vapor can occupy. The kinetic energy produced during the compression process further heats the coolant. While this can seem counter-intuitive, it prepares the refrigerant for cooling.

Step 3: Transfer of Heat Outside

Next, the now pressurized vapor travels to a condenser, which is also located outside, to recool the refrigerant. The condenser is exposed directly to the outside air. Even in the hottest weather, the outdoors is cooler than the superheated coolant. So, the ambient air can actually absorb heat from the refrigerant, allowing it to cool and change back into a liquid. Just like the evaporator, the condenser includes a set of copper coils. The vaporized refrigerant travels through these coils while a fan blows ambient air across them, allowing the heat to dissipate. By using many coils, the unit increases the amount of time the refrigerant spends near the blowing fan. The heat is then expelled or "dumped" outside.

Step 4: Refrigerant Cools and Recycles

Once the refrigerant returns to its liquid state, it travels inside, back to the evaporator. Even though the condenser has thoroughly cooled the refrigerant, it is still too warm and high-pressure to cool the air inside your home. So, before reaching the evaporator, it travels through an expansion valve. This valve controls the flow of refrigerant back into the evaporator and helps to cool the refrigerant further so it can condition your air. The expansion valve depressurizes the refrigerant, allowing it to cool rapidly because pressure and temperature have a direct relationship. Just as the compressor forces the coolant to superheat, the expansion valve allows the substance to cool. By restricting the flow of the refrigerator fluid into the evaporator, a smaller amount of the liquid takes up more space. The refrigerant expands, and the temperature drops in response. The refrigerant can then recycle back into the evaporator, cooling the air further. The entire process happens continuously, and the AC unit will keep taking in air until it reaches the desired temperature.

Different Types of Air Conditioners

While all air conditioner work functions follow the same basic principles to cool air, there are many types of AC systems. Each has a different price, size and energy efficiency rating. Here are the primary types of air conditioners:
  • Central split systems: Central air is considered a split system because half of the system is inside, and the other half is outdoors. Central air conditioners have an interior air handler that cools the air. They also have an exterior compressor and condenser unit that expels heat. Some split systems can cool and heat air using the same unit.
  • Ductless split systemsDuctless split systems have smaller footprints than central air units. They are great for houses that don't have ductwork. An indoor, wall-mounted unit connects to the outdoor compressor and condenser via tubing. Houses cooled this way have one cooling unit in each room.
  • Window units: A window air conditioning unit will cool a single room and the entire conditioning system is contained in a box. The compressor and condenser exhaust heat from the outward-facing side while the evaporator sends cool air into the room through the front-facing vent.
  • Portable units: Portable air conditioners are entirely indoor air conditioner units, and are a fantastic temporary solution if your central air system breaks. You can relocate a portable air conditioner around the house and take it with you when you move. They funnel hot air through an exhaust hose connected to a window. Basically, you make the air conditioner work where you need it, and not where you don't.
  • Package units: A package air conditioning system contains all the components of an AC system in one unit. It is also a completely outside AC unit, so you won't have to install any indoor elements.
  • PTAC and wall units: Package terminal air conditioners (PTACs) are often found in hotel rooms because they allow for each room to have its own temperature control. While they are found more often in commercial properties, you can use one to supplement your central air system. Like PTACs, wall units are installed through a wall. They resemble window units except that they will stay installed year-round.
How Does a Portable Air Conditioner Work?

How Does a Portable Air Conditioner Work?

An in-room air conditioner or portable AC system uses the same principles as central air. Instead of an outside unit for compressing or condensing, they discharge heat through exhaust tubes. Some models use one hose, while others are dual-hose systems. In a single-hose unit, hot air will be sent outdoors, creating negative pressure indoors. In a dual-hose system, one hose expels hot air, and the other brings air in from outdoors to balance the negative pressure. While all air conditioner work gets rid of moisture in the air, portable air conditioners have several ways of doing so.
  • Self-evaporating models: The most advanced portable air conditioners evaporate moisture and send it through the exhaust hose. If you have a self-evaporating model, you will rarely need to empty collected water.
  • Gravity drain and condensate pump models: Some portable AC units include a drain hose. With these models, you'll have to hook up the drain to the air conditioner and thread it into a bucket or floor drain. You might also attach a pump accessory to the hose to help drain the moisture.
  • Manual drainage models: The most basic portable air conditioners have buckets inside the units that collect water. They need to be emptied regularly, sometimes as frequently as every eight hours. To do this, you'll need to shut the unit off, remove the bucket and pour the water out.

When to Replace Your Air Conditioner

If you've been wondering how air conditioners work, you may also be looking for repairs or replacement. When the components of your air conditioner stop working, it may be time to consider a new one. While many issues can be repaired, once your unit gets old, a replacement may be more cost-effective. You definitely don't want to make an air conditioner work harder than it should, since they'll waste more money and energy doing so. Here are some indications it's time to replace your AC unit:
  • When it's not energy-efficient: At some point, the extra costs of making an inefficient air conditioner work begin to outweigh the cost of buying a new, more energy-efficient HVAC system. As your air conditioner gets older, it begins to lose its energy efficiency. If you start to notice higher utility bills, more humidity or frequent AC unit breakdowns, you might consider replacing your air conditioner.
  • When it's more than 10 to 15 years old: According to the U.S. Department of Energy, the average lifespan of an air conditioner is 15 to 20 years. The number of years you get out of your system can depend on the manufacturer and the specific model you own. Either way, you can save between 20% and 40% on your cooling costs by switching out a 10-year-old air conditioner with a newer, energy-efficient model.
  • When you don't get enough cold air: The biggest sign you need a new air conditioner when it's not doing its job. In some cases, you might not be getting any cold air at all. Low airflow can indicate an issue with the vents. While this problem may be repairable, you should weigh the cost of repair against the cost of replacement when the unit is on the older side. If some rooms in your house aren't being cooled, you may only need to replace your thermostat.
  • When you notice leaks: Air conditioners condense and remove moisture from the air. So, while condensation around the air conditioning unit is normal, a pool of water is a sign of a more significant problem. Leaking refrigerants can pose a health risk, and excess water can damage your floors, walls and furniture.
  • When you hear unusual sounds from the unit: Some sounds can indicate broken components. When your air conditioner begins making loud noises, such as grinding, banging or squealing, get your air conditioner looked at by a professional. You may have a slipped belt or broken motor bearings.
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Whether you're looking to install central air or any other type of air conditioning unit, trust Ingrams Water & Air. We offer lifetime tech support, so you can be confident in your purchase. Plus, you can always turn to us whenever you need air conditioner replacement parts or accessories. Make an air conditioner work for you, today!
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