How Does an Air Conditioner Work?

HVAC Logo IconBy Tom MoorMarch 18, 2024
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If you’re like many homeowners, you probably don’t give your air conditioning system much thought as long as it’s performing properly – keeping you cool and comfortable during the summer while also ensuring energy bills stay low. But understanding how an air conditioner operates is beneficial, empowering homeowners to make informed decisions about maintenance, energy-efficiency upgrades, and potential repairs. answers the question, “How does an air conditioner work?” and delves into other important homeowner insights, such as the different types of cooling systems and the benefits of adopting smart air conditioning practices.

A Brief Overview of Air Conditioning

An air conditioner is a mechanical system designed to regulate indoor temperature and humidity levels to create a comfortable indoor environment. Residential air conditioners, which typically consist of indoor and outdoor units, vary in complexity and size, ranging from small window units to large central cooling systems, capable of maintaining comfort throughout entire homes.

Modern air conditioning systems became mainstream in the United States during the 1950s and have steadily grown in popularity. Today, it’s estimated that nearly 90% of American homes use some form of air conditioning during the warmer months, especially in regions where the heat and humidity can become intolerable.

How Does an AC Work?

An interesting fact about air conditioning systems is that – contrary to common belief among many homeowners – they don’t actually produce cool air like furnaces produce heat. Instead, air conditioners function by circulating refrigerant, which absorbs heat from indoor air and releases it outdoors, effectively cooling the interior space.

Let’s take a more in-depth look at how an air conditioner works:

Evaporator Coil Function

Warm air from your home is drawn into the air conditioner and passes over the cold evaporator coils. As the air moves across these coils, the refrigerant inside absorbs the air’s heat. Simultaneously, moisture in the air condenses on the coils, reducing humidity levels and enhancing the cooling effect. This process transforms the refrigerant from a cool liquid into a hot vapor, effectively cooling the air circulating in your home.

Compressor Operation

The heated refrigerant vapor is then directed to the compressor, typically located in the outdoor unit of the air conditioner. The compressor plays a crucial role in the cooling process by compressing the refrigerant vapor. As the vapor is compressed, both its temperature and pressure increase significantly. This increase in temperature and pressure is essential for facilitating the transfer of heat from indoors to outdoors, where it can be dissipated effectively.

Condenser Operation

Once compressed, the refrigerant vapor moves to the condenser coils, also located in the outdoor unit. Here, the hot refrigerant vapor releases its heat to the outdoor air. The condenser coils help facilitate this heat transfer process, while a fan blows outdoor air over the coils, further enhancing cooling efficiency. As the refrigerant releases heat, it undergoes a phase change, transitioning from a vapor back into a liquid state.

Expansion Device Function

The now-cooled refrigerant, in its liquid form, travels back to the indoor unit through a copper tube. Along this journey, it passes through an expansion chamber which serves to regulate the flow of refrigerant, controlling its rate as it re-enters the indoor unit.


Air conditioner condenser unit

What Are the Different Types of Cooling Systems?

Most people envision air conditioning systems with an outdoor condenser unit and an indoor air handler. In reality, there are many different types of air conditioners that can be used to cool a home.

Central Air Conditioners

Central ACs utilize an outdoor condenser and an indoor air handler (that also works with the furnace or heat pump) to deliver cool air indoors.

Heat Pumps

Heat pumps can provide both heating and cooling for year-round comfort, and are an option for central air conditioning. Backed by federal tax credits and rebates, heat pumps have skyrocketed in popularity in recent years as an energy-efficient and environmentally friendly alternative to traditional HVAC systems.

Ductless Mini-Split Air Conditioners

Mini-splits utilize individual air handlers – instead of ductwork – which are installed throughout the home. They are connected to an outdoor heat pump to provide zoned cooling in the specific areas that need it. Mini-splits can also provide both heating and cooling functions.

Portable and Window Air Conditioners

Portable and window ACs are additional options for space cooling – they are not a whole-home cooling solution. They are ideal options to cool spaces between 150 and 500 square feet.

Understanding How AC Systems Work Can Enhance Comfort, Increase Savings, and Improve IAQ

Learning how air conditioners work can provide homeowners with valuable insights.

  • Adopting a Maintenance Routine. Homeowners well-versed in how their air conditioners operate understand the importance of annual AC maintenance, typically performed each spring. During an AC tune-up appointment, a qualified HVAC technician inspects and adjusts various components, ensuring optimal performance and efficiency of the system. They can also catch minor issues before they lead to bigger, more expensive issues down the road.
  • Catching Problems Early On. By familiarizing themselves with the components involved in the cooling process, homeowners can also identify potential issues early on, preventing costly repairs and breakdowns in the future. For example, by recognizing signs such as a mildew smell, which could indicate an AC leak, or unusual noises, signaling a broken component, homeowners can preemptively address issues, thus averting potentially costly repairs in the future.
  • Adopting Energy-Efficient Practices. Implementing a few energy-efficient practices can significantly enhance both the health and efficiency of your air conditioning system. These measures may encompass routine air filter replacements and energy-saving thermostat adjustments.

Overall, a clear understanding of air conditioning principles equips homeowners with the tools they need to create a comfortable, healthy, and cost-effective indoor environment for themselves and their families.

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