Air Cooled Split Units

Small air conditioning units are often called direct inspection units. All the common refrigeration and air conditioning machines use expansion of refrigerant to remove heat. The dx, or direct expansion units are the simplest in construction. In thermodynamic terms, when the state of the refrigerant changes from liquid to vapor, latent heat is absorbed from the surroundings. That is why the expanded refrigerant vapor feels so cold. This portion of the air conditioning unit is called the evaporator. Heat from the room is absorbed here. There is another portion where heat is expelled to the atmosphere. This portion is called the condenser.

Air is very often used to cool the hot refrigerant gas at the condenser because it is a simple method. It will work even in desert areas with very limited water supply. It works in motor cars, and other road vehicles. All you need is electrical supply to drive the cooling fan.

A compressor is used to pump the refrigerant gas inside the refrigerant circuit. An expansion valve is used to change of state of the refrigerant from liquid to vapor. The four components of compressor, condenser, expansion valve, and evaporator make up the basic direct expansion air conditioning unit. Other pieces of equipment are the control and protection systems, condenser cooling fans, evaporator blower,

Air-cooled split units are the most common dx units. They are called split units because the machine components of the refrigerant circuit are separated. The condenser and compressor are put outdoors, while the evaporator and expansion valve are placed indoors.

Although the concept of the direct expansion air conditioning unit is simple, special skills and procedures are needed to install and troubleshoot them. A skillful dx air conditioning service personnel must be able to do copper tube brazing, vacuuming, refrigerant gas and lubrication oil charging, leak check, electrical work, a bit of manual power drilling on concrete, and a lot of climbing around on high places.