Types
The two primary types of copper tubing for air conditioning systems are hard and soft tubing. Hard tubing, which is also known as drawn temper tubing, is harder due to the process by which the tubing has been heated and treated. Soft tubing, or annealed temper tubing, has been heated in such a way that the strength of the tubing has been altered. Both types use similar types of fittings, but each is more suitable for specific applications.
Range
Copper tubing used in air conditioning systems ranges from 1/8-inch to 1-3/8 inches in nominal size. The nominal size is the outside diameter of the pipe. Wall thickness will actually vary somewhat depending upon this nominal size. Annealed temper tubing has a wider range, from 1/8-inch to 1-3/8 inches, whereas drawn temper tubing is limited from 3/8-inch to 1-3/8 inches. The inside diameter and thickness of the pipe walls vary as well. Annealed tubing usually has a larger inside diameter, which means that it also has thinner walls that take up less space.
Fittings and Type
Both annealed and drawn temper tubing can be used with soldered fittings as well as with flared fittings. The Copper Development Association recommends the use of types L or ACR copper tubing for air conditioning applications. It also recommends using the manufacturer's recommended type if it differs from one of these two. The type that is chosen is based on its properties and its effect on fluid mechanics.
Copper Use
The use of copper in air conditioning systems stems from a number of different reasons based on the manufacturers' preferences. Copper is both economical and durable; moreover, its lightweight nature and malleability make it a logical choice in air conditioning applications. Furthermore, copper can be easily joined, and its ability to be recycled makes it an environmentally-friendly choice as well.