March 2, 2022

How Do Central Air Conditioners Work?

The central air conditioner is one of the most common forms of cooling equipment. But have you ever thought about how it actually works? How can a piece of machinery “generate” cool air for your HVAC system? Rather than producing cool, dry air, your air conditioner instead absorbs ambient heat from indoors and transports it outside your home. The most important components within your air conditioner are responsible for this process. Let’s take a closer look at what central air conditioners consist of, and how these parts work together to help you stay cool.

Central Air Conditioners Consist of an Indoor Unit and an Outdoor Unit

The key components in your central air conditioner are divided between two housing units. One is placed outdoors and the other indoors. The indoor unit is usually called an air handler and is installed near other HVAC machinery, such as your furnace. This separation is important for the proper cycle of absorbing and dissipating heat. Otherwise, the heat would just be dumped right back inside your home.

The Indoor AC Unit Collects Heat and Sends Cool Air into the Ductwork

The air handler portion of your central air conditioner is responsible for absorbing the latent heat in the air inside your home. As the heat is captured, moisture is also removed and drained away from the rest of the HVAC equipment. The cool, dry air is sent through your home’s air ducts while the heat is directed toward the outdoor unit. Here are the primary components you’ll find in your central air conditioner’s indoor unit:

  • Evaporator coil: The evaporator coil takes advantage of heat’s natural behavior of being drawn toward cooler temperatures, which in this case is the refrigerant. As a cool mist, the refrigerant can quickly absorb heat before being sent to the outdoor unit.
  • Blower motor: The blower motor turns the fan responsible for moving warm air across the evaporator coils. This fan is also what sends cool, dry air into the air ducts.
  • Expansion valve: The refrigerant returns from the outdoor unit as a hot liquid. The expansion valve allows a steady flow of coolant to pass through it and causes a large and sudden drop in pressure. This pressure change converts the coolant back into gaseous form and allows the cooling process to begin again.

The indoor unit also houses the HVAC system’s air filter. While not a part of the cooling process, the air filter is still important. It captures airborne particles like dust, allergens and even bacteria before it can travel through the ductwork.

The Outdoor Unit Emits the Heat and Compresses the Refrigerant

The outdoor cabinet uses pressure and airflow to force heat out of the refrigerant. This process requires several key components and revolves around changing the coolant’s state of matter. It starts in a gaseous state and is pressurized into a liquid one before rapidly shifting to a gas again. This sudden change in its state of matter is the same principle for why sweating helps cool your body down. The key components in the outdoor unit include:

  • Compressor: This powerful pump is what draws the refrigerant from the air handler toward the outdoor unit. This also produces high pressure, which increases the temperature of the gaseous coolant. The ultimate destination of this hot refrigerant is the condenser coil.
  • Condenser coil: These coils perform a similar function to the indoor air handler’s evaporator coils, except in the opposite direction. A large fan on top of the outdoor unit blows air across the coils, drawing the heat up and out of the cabinet and into the air outside.

At this point in the cooling system cycle, all that’s left is for the AC refrigerant to return to the indoor air handler. With the expansion valve converting the coolant into vapor again, the process can start over.

This Cycle of Evaporation and Condensation Keeps Your Home Cool

As long as the refrigerant supply remains consistent, the cooling cycle will function normally. Thanks to its ability to retain and expel heat, we can now keep our homes cool through the warmer months of the year.

If you’re considering a new air conditioner or need a problem with your existing AC resolved, why not call Home Heating & Cooling? Our technicians are fast, efficient and dedicated to your sense of comfort. Give us a call today at 618-416-0111.

Home Heating & Cooling
1450 Frontage Road, O'Fallon, IL 62269 USA
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