How Air Conditioners Work
Air conditioners employ the same operating principles and basic components as your home refrigerator. An air conditioner cools your home with a cold indoor coil called the evaporator. The condenser a hot outdoor coil, releases the collected heat outside. The evaporator and condenser coils are serpentine tubing surrounded by aluminum fins. This tubing is usually made of copper. A pump, called the compressor, moves a heat transfer fluid (or refrigerant) between the evaporator and the condenser. The pump forces the refrigerant through the circuit of tubing and fins in the coils. The liquid refrigerant evaporates in the indoor evaporator coil, pulling heat out of indoor air and thereby cooling the home. The hot refrigerant gas is pumped outdoors into the condenser where it reverts back to a liquid giving up its heat to the air flowing over the condenser's metal tubing and fins.

Most central air conditioning units operate by means of a split system. That is, they consist of a "hot" side, or the condensing unit including the condensing coil, the compressor and the fan which is situated outside your home, and a "cold" side that is located inside your home. The cold side consists of an expansion valve and a cold coil, and it is usually part of your air handler. The air handler blows air through an evaporator coil, which cools the air. Then this cool air is routed throughout your home by means of a series of air ducts.

Basic Operations
Air conditioning includes both the cooling and heating of air. It also cleans the air and controls the moisture level. An air conditioner is able to cool a building because it removes heat from indoor and transfers it outdoors. A chemical refrigerant in the system absorbs the unwanted heat and pumps it through a system of piping to the outside coil. The fan, located in the outside unit, blows outside air over the hot coil, transferring heat from the refrigerant to the outdoor air.

The compressor is the "heart" of the system. The compressor acts as the pump, the refrigerant flows through the system. It draws in a low-pressure, low-temperature, refrigerant in a gaseous state and by compressing this gas, raise the pressure and temperature of the refrigerant. This high-pressure, high temperature gas then flows to the condenser coil.

The condenser coil is a series of piping with a fan that draws outside air across the coil. As the refrigerant passes through the condenser coil and the cooler outside air passes across the coil, the air absorbs heat from the refrigerant which causes the refrigerant to condense from a gas to a liquid state. The high pressure, high-temperature liquid then reaches the expansion valve.

The expansion valve is the "brain" of the system. By sensing the temperature of the evaporator, or cooling coil, it allows liquid to pass through a very small orifice, which causes the refrigerant to expand to a low-pressure, low-temperature gas. This "cold" refrigerant flows to the evaporator.

The evaporator coil is a series of piping connected to a air handler that blows indoor air across it, causing the coil to absorb heat from the air. The cooled air is then delivered to the house through ducting. The refrigerant then flows back to the compressor where the cycle starts over again.

Heating and cooling your home uses more energy and drains more energy dollars than any other system in your home. No matter what kind of heating, ventilation, and air conditioning system you have in your house, you can save money and increase comfort by properly maintaining and upgrading your equipment. By combining proper equipment maintenance and upgrades with appropriate insulation, weatherization and thermostat settings, you can cut your energy bills and your pollution output in half. Saving money on your energy bills will depend on four major factors:

Energy efficiency of your system
Managing system operation
Simple system maintenance