An air conditioner is able to cool a home because it removes heat from inside the house and transfers it outdoors. A chemical refrigerant in the system absorbs the excess heat and pumps through a system of piping to the outdoor coil. The fan, located in the outside unit, blows outside air over the hot coil, transferring heat from the refrigerant to the outdoor air.
Air conditioning systems have four basic mechanical components:
Most central air conditioning units operate by means of a split system. They consist of a condensing unit: including the condensing coil, compressor, and the fan, this unit is outside your home. The air handler consists of a metering device, evaporator coil and blower motor to deliver cooled air to your home.
The compressor is the heart of the system; it acts as the pump, causing the refrigerant to flow through the system. It draws in the low pressure, low temperature refrigerant in a gaseous state and by compressing this gas, it raises 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 coil, the cooler outside air passes over the condenser coil, the air absorbs heat from the refrigerant which causes the refrigerant to condense from a gas to a liquid. The high pressure, high temperature liquid then reaches the expansion valve.
The expansion valve is the brain of the system. 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 allow pressure, low temperature gas.
The evaporator coil is a series of piping inside the air handler. Air blowing across the coil causes the coil to absorb heat from the air. The refrigerant then flows back to the compressor where the cycle starts over.