How Your Split-System Air Conditioner Works

Most of us have an air conditioner, but few of us know how it actually works. Having an idea of how your air conditioner keeps you cool can help you troubleshoot problems with your system and communicate with HVAC specialists when you have questions or need repairs.

The Refrigerant

Refrigerant is a chemical that has the ability to convert from liquid to gas and back again with ease. The refrigerant is like a city bus that runs its prescribed route, delivering people to their destination. Except instead of people, the refrigerant picks up heat from inside your home and deposits it outdoors.

The Ducts

The big duct on the side of your air conditioner is connected to the air return vents in your home. Air moves through the duct, passes through the air filter, and the fan blows the warm incoming air over the evaporator coil. The heat is removed from the air, which then enters the supply ducts and gets distributed throughout your home.

The Evaporator Coil

Located in your indoor unit, the evaporator coil is the bus stop where the heat climbs aboard. The refrigerant is a cool liquid as it enters the coil through a tiny hole, which causes the pressure to drop and the refrigerant to turn into a gas. As air is blown over the coil by the fan, the cool gas extracts the heat from the air and carries it to the outdoor unit. At the same time, humidity in the air condenses on the evaporator coil and drips into the condensate pan below.

The Compressor

Located in the outdoor unit, the compressor is the gateway to the condenser coil. The refrigerant is a low-pressure, cool gas when it enters the compressor, which squeezes it and turns it into a high-pressure, hot gas.

The Condenser

The high-pressure, hot gas enters the condenser. The outdoor fan blows air over the condenser coil, and the heat inside the refrigerant flows out and travels through the fins on the outdoor unit’s casing, which acts like a radiator to dissipate the heat. As the heat leaves, the refrigerant turns back into a cool liquid and travels back to the evaporator coil to pick up more passengers.

Efficiency Factors

There are a number of factors that determine the efficiency and effectiveness of your air conditioner.

Refrigerant level. Without the exact right amount of refrigerant, your system won’t operate properly. If your system isn’t cooling very well or the evaporator coil freezes over, it may signal a refrigerant leak, which will need to be repaired right away to avoid damage to your system and the environment.

Dirty coils.

Dirt buildup on the evaporator coil acts like insulation, making it difficult for the refrigerant to effectively remove heat from the air. Additionally, a dirty condenser coil will have trouble releasing all of the heat.

The air filter.

The air filter removes dust from incoming air so that it doesn’t get inside the system and coat the essential components, including the blower assembly and evaporator coil. Inspecting the filter monthly and replacing it when it’s dirty is essential for keeping your air conditioner clean and for maintaining proper airflow.


A dirty filter or obstructions in the ducts can restrict airflow, which results in a loss of efficiency and comfort. Restricted airflow can cause a lot of problems for your system, including overheating.


Annual preventive maintenance is essential for ensuring your system is clean and its components are working properly. A neglected air conditioner will lose between 5 and 15 percent of its efficiency for every year that it’s not tuned up.

For more expert information about the inner workings of your air conditioner, or to schedule your spring maintenance visit, please feel free to contact us at Comfort Control, Inc.

Keep Your Family Comfortable With Comfort Control

Licensed Professionals
Prioritize Comfort & Safety
30+ Years of Experience
Satisfaction Guaranteed