Air Conditioning and Refrigeration Tubing

Most tubing used in refrigeration and air conditioning is made of copper. However, some aluminum, steel, stainless steel, and plastic tubing are also used. Copper tubing is generally used for plumbing, heating, and refrigerant tubing, Steel and aluminum tubing are used for gas and frequently for hot water heating. Plastic pipe is often used for waste drains, condensate drains, water supplies, water-source heat pumps, and venting high efficiency gas furnaces. All tubing used in air conditioning and refrigeration work is carefully processed to be sure that it is clean and dry inside. The ends must be kept sealed until it is used.

Copper Tubing

Most copper tubing used in air conditioning and refrigeration work is known as Air conditioning and refrigeration (ACR) tubing. Copper tubing is available as soft- or hard-drawn copper. Soft copper tubing may be bent or used with elbows, tees, and other fittings. Hard-drawn tubing is not intended to be bent and is used only with fittings to obtain the necessary configurations. This tubing is available in four standard weights: K, L, M and DWV. K-type copper is heavy duty with a thick tubing wall. L-type copper is considered medium weight and is the ACR tubing is sized by its outside diameter.

Type used most frequently. M is a lightweight copper and is not commonly used in our industry. DWV copper stands for drain, waste, and vent and is also a lightweight copper not typically used in the HVACR industry as far as refrigerant carrying applications are concerned.   ACR tubing is usually charged with gaseous nitrogen. This keeps the tubing clean and dry until it is used.  All tubing ends should be plugged immediately after cutting a length from the piece.

Soft copper Tubing

Soft copper Tubing is used in domestic work and in some commercial refrigeration and air conditioning work. It is annealed (heated and then allowed to cool). This makes it flexible and easy to bend and flare. Being easily bent, this tubing must be supported by clamps or brackets. Soft copper tubing is most frequently used in connection with flared fittings and soft soldered fittings. Sizes most generally used are 3/16, 1/4, 5/16, 3/8, 7/16, 1/2, 9/16, 5/8 and 3/4 outside diameter (OD). Wall thickness is typically particular in thousandths of an inch. Both soft and hard drawn sizes are the same as the dimensions. Outside diameter size for this tubing is the real outside diameter of tube. Soft copper tubing may be worked to give it sure properties. It can be hardened by constant bending or hammering. This is called work hardening.

Hard Drawn Copper Tubing 

Hard drawn copper tubing is used in commercial refrigeration and air conditioning applications. Being hard and hard, it needs few clamps or supports, mostly in larger diameters. Hard tubing should not be bent. Use straight lengths and fittings to form required tubing connections. Hard drawn refrigeration tubing joints should be brazed. Soft solder should be used only on water lines. Hard drawn tubing is supplied in 20' lengths. It is available in the same diameters and thicknesses as soft copper tubing.

Steel Tubing 

Some thin wall steel tubing is used in refrigeration and air conditioning work. These sizes are basically the same as for copper tubing. Connections may be made on steel tubing by using either flared joints or brazed joints. Copper or brass tubing must not be used with refrigerant R-717 (ammonia). Use steel tubing instead. There is a chance of chemical reaction (corrosion) between ammonia and copper. Two types of steel tubing are in common use. One type has a double lap brazed construction using SAE 1008 mild steel. The other is butt welded, using the same type steel.

Stainless Steel Tubing 

Stainless steel tubing comes in the typical refrigeration tube sizes. The most common sizes are listed in the table; it may be easily connected to fittings by flare fittings or brazing. Stainless steel tubing No. 304 is commonly used. This is a low carbon iron alloy containing 18% chromium and 8% nickel. It is often used in food processing, ice cream manufacture, milk handling systems, and the like. Type 304 stainless steel is not magnetic.

Plastic Tubing

Polyethylene is one of the most common substances used in the manufacture of plastic tubing. Therefore, never use this tubing in installations where fluid temperature goes beyond these limits. In general, polyethylene tubing is not used in the refrigerating cycle mechanisms. It is used for cold water lines, water-cooled condensers, and the like. Polyvinyl chloride (PVC) pipe is used mainly in high pressure applications at low temperatures for water and gas. Special fittings are available for connecting polyethylene tubing to refrigeration and air conditioning mechanisms.

Flexible Tubing (Hose) 

In many refrigeration and air conditioning applications, the liquid lines and suction lines must be flexible; Air conditioning equipment on motor vehicles requires flexible tubing. This type of hose is made from a variety of special materials. Such materials do not age and remain flexible. These materials do not allow fluid to leak through the hose wall. They are easy to attach to fittings.

SAFETY Tip

• Use care while reaming tubing; the burr can stick in your hand.
• Be careful while using a hacksaw; the blade is sharp.
• Do not allow your bare skin near the flame of a torch or near material that has just been soldered, brazed, or welded; the 5000°F and higher temperatures can cause severe burns.
• Always wear eye protection while performing any task where particles may be in the air.
• Use extra caution with the oxyacetylene heat source.
• Be aware of flammable materials in the area where you are soldering or brazing.
• Pipe cutting and threading creates burrs that can cut your skin and otherwise be dangerous; use caution.
• Do not breathe excessive amounts of the adhesive used for plastic fittings.