How Air Conditioning Works

Air Conditioners: How Do They Work?

An air conditioner is a system that cleans, circulates, cools and dehumidifies (removes moisture from) indoor air.

The Filter

All air conditioners incorporate some sort of filter. A filter cleans air by separating dust and other small particles from air that passes through it. Filters are of various types, but the common household filter is made of loose paper mesh. Filters should always be replaced regularly to ensure peak air conditioning performance and maximum cost savings.

The Air Handler

An air handler is a fan/blower that is incorporated into an AC system. The air handler circulates air; it draws air in from the living space and passes it through the cooling system where it is forced back into the living space. You may have noticed that your air conditioning system has a “fan” setting apart from a cool setting. This setting activates the air handler and passes air through the filter, but does not cool it.

In troubleshooting an air conditioning system, if the fan setting does not produce adequate pressure at return vents, forces air with odors, or creates excessive noise, you may have a worn out air handler or may need a filter change.

Air handlers also can be adjusted to blow harder or softer. Softer settings reduce noise, but may not cool either as effectively or efficiently. Air handlers that blow too hard can also reduce efficiency.


Refrigeration is the component of an air conditioning system that brings familiar relief from the head. Refrigeration obviously cools air, but also dehumidifies air. A wall unit has a single refrigeration unit. A central air conditioning system, however, divides the refrigeration system into two parts: an indoor coil, and an outdoor condenser connected by refrigerant-filled piping. Refrigerant is a pressurized gas whose principal chemical property is that it absorbs and releases heat very efficiently when pressurized.

First, the interior coil (in which low-pressurized refrigerant passes) absorbs heat from the warm interior air as the air passes over, or through, the coil. The heated refrigerant, which always flows in a circle between coil and condenser, passes to the condenser. Then, the outdoor condenser unit pressurizes and condenses the refrigerant, which readily releases its heat when it is passed through a series of cooling fins. An outdoor condenser looks and operates much like a car’s radiator. The cooled refrigerant then cycles back into the home, through the coil, where the process occurs continually.

The air handler blows interior air over the coil, which cools and dehumidifies the air.

Want to learn more? Read our Air Conditioning Troubleshooting Guide.