Air Conditioning 101

Air Conditioning 101

How Central Air Conditioning Systems Work

Ken, the eComfort Product Expert
Product Expert

Can you imagine life without air conditioning? Sweltering heat waves that can melt the rubber on your shoes, cook an egg on the dashboard of your car, and make it nearly impossible to have a good night's rest -- sounds miserable!

Let's face it, life without A/C wouldn't be the same. Did you know, that before the 20th century, ice was actually harvested for refrigeration? It was cut into 1-ton blocks, delivered throughout the country and used in 'ice-boxes' to keep food fresh. Thankfully today, refrigeration has been drastically improved since its introduction in 1834.

By knowing how your home's A/C system works, you'll be able to make it run better and longer, and if it should break during the dog days of summer, more confident finding a replacement.

How Central Heating and Cooling Systems Work

Image: Goodman Manufacturing

Central A/C CondenserWhat is Central Air Conditioning?

Since the 1960s, central air conditioning systems have been the most common style of cooling in America.

Best characterized by the condenser unit outside (pictured) and ducts carrying cool air throughout the home, a central air conditioning is sometimes referred to as a "split-system" because the indoor and outdoor components are separated.

How It Works

Similar to how a sponge soaks up water, central air conditioners absorb the heat from inside the home and eject it outside through a process called "the refrigeration cycle."

It's easy to understand how an air conditioner works once you see how the parts operate together.

Parts of an Air Conditioning System

Split into two parts; a system will contain an outdoor condenser unit (below) and a coil housed on top of the furnace or inside air handler. The outdoor condenser, which does most of the work, operates in tandem with the air handler/furnace that distributes the conditioned air into rooms of your home. Take a look at the cutaway diagram below to see what is inside an A/C condenser.

Air Conditioner Components Infographic
Image: Goodman Manufacturing

Air Handler Unit

The Refrigeration Cycle

The cooling process starts when the thermostat detects the interior temperature has risen above the setpoint. It signals the control board in the air handler and goes into action. 


  1. The internal blower draws in the hot, moist indoor air from the return ducts into the air handler/furnace cabinet to be conditioned.

  2. Dirty air entering the cabinet first passes through an air filter that traps dirt and debris.

    Evaporator Coil
  3. The clean air then passes through the evaporator coil. Using metal fins to increase its surface area, the evaporator coil extracts heat and moisture from the warm air as the air passes through it. The clean, cool air is circulated throughout the home. 

  4.  A pair of copper tubes containing refrigerant, called a Line Set, connect the indoor coil with the outdoor condenser.

  5. The condenser dissipates the heat trapped inside the line coming from the evaporator coil by cycling it through its coils where a fan at the top pushes air to accelerate the process. The refrigerant is then compressed and travels back to the indoor evaporator coil, where the cooling process continues.


HVAC Cheat Sheet

It's a good idea to familiarize yourself with the technical language used by HVAC professionals to understand your system when it comes to making repairs or buying a new unit.

  • HVAC - Stands for heating, ventilation, and air conditioning. This acronym is used to categorize all equipment used to regulate air temperature, humidity, and air quality.

  • Split-System - In reference to parts of the system operating both indoors and outdoors. In a split system, the condensing unit is found outside.

  • BTU - British Thermal Units - a measurement of how much heat energy can be removed from the air in an hour.

  • Ton - A measurement that refers to the cooling capacity your unit can provide under normal conditions. 1 Ton is equal to approximately 12,000 BTU's. Tons are often used when sizing a unit for your home, which can be determined based on the square footage needed to be cooled or heated.

Unmatched Expertise

Conveniently, the furnace, air conditioning, and electrical systems all work automatically, without us needing to fumble around in the basement or worse, a hot attic. Until something goes wrong.

Learning about your air conditioning system may seem overwhelming at first, but once you have the basics down, you'll be able to understand not only how your system works, but also decipher jargon to make buying a replacement simple.

If you have questions about your central air conditioner, we'd love to hear from you.

NEXT: Central Air Buying Guide

Central Forced-Air Buyer's Guide

HVAC-101 | Gas Furnaces-101 | Heat Pumps-101 | Packaged Units-101 | Air Conditioning-101 | Air Handlers-101

Ken, the eComfort Product Expert
Product Expert
Was this article helpful?