• The most important part of an air conditioning unit is the air compressor, which pumps the cooled air through the system. The other job that the air compressor accomplishes is to compress the low-pressure refrigerant into high-pressure gas. There are several different types of compressors used in air conditioning units depending on the size of the area being cooled.
  
  

Scroll Compressors

• Scroll compressors are one of the most commonly used types of compressors because they are highly efficient. Scroll compressors run quietly and are less likely to develop leaks than other types of compressors. The way that this efficiency is achieved is due to the design of the compressor, but it also has built-in mechanisms that help it run effectively. The refrigerant is moved by air that is compressed between two cogs that are designed to form curved gas pockets. One spiral cog continuously moves around the other cog in order to drive air through the exhaust. The gas is taken into the pockets that gradually get smaller and this process compresses the gas and makes it hot. Once it is sufficiently compressed, it is then moved to the condenser.
  
  

Piston or Reciprocating Compressors

• Piston or reciprocating compressors are still in use but not as widely as they were in the past. Their main use is for industrial air conditioning units. They are not typically utilized for residential use because they are much louder than scroll compressors. The reason for the high noise level is the fact that they use pistons that are driven by a motor to compress the gas in a cylindrical chamber. The gas is taken into one end of the cylindrical chamber and then the piston enters the chamber and compresses the gas. Once compressed the gas leaves the far end of the chamber and moves on to the condenser. Reciprocating compressors are not only noisy; they are less efficient than other types of compressors because they are not good at supplying a steady flow of refrigerant.
  
  

Screw Compressors

• Screw compressors are also popular air compressors because of their simple and low-maintenance design. This type of compressor uses two screw-shaped spindles that are intertwined and rotate in opposite directions. The refrigerant enters the chamber and is compressed between the rotating screws. Because the screws rotate in opposite directions, they cause the gas to be pulled into the chamber and then pushed out to the condenser. This system offers a smooth, continuous flow of air but it is still not as efficient as a scroll compressor.