Tubing and Fittings in HVACR
The copper tubing and fittings used in air conditioning and refrigeration are designed and processed for HVACR and are often charged with nitrogen. The nitrogen keeps the tubing clean and dry preventing the onset of oxidation/corrosion. This type of tubing is used for hot and cold water supplies and the refrigerant lines found in HVAC systems.
Soft Copper Tubing
Soft copper tubing will bend easily and can be forced around obstacles and construction. Copper such as this is said to be annealed. In the world of metallurgy, copper, brass, and silver are cooled slowly in the air so they remain in such a state as to be formed or shaped in definite ways. It is more expensive when it is annealed. This type of copper is used in split-system HVAC units and heat pumps. They are easily flared for connections.
Hardened Copper Tubing
Hardened copper tubing is used for water lines, commercial refrigeration and HVAC. This type of tubing is joined using grooved, compression, crimped, or sweat connections. The runs are mostly straight except where it must be bent to go around construction. Elbow fittings are used to make the bend.
Copper Tubing Sizing
Copper tubing is usually available in either soft or hard presentations.
Type K is the thickest of the types and is often used underground. It is coated or may by suited with a polyethylene coating. It is usually available as hard drawn straight sections and in rolls that have been annealed.
Type L is thinner than type K and is used for water supply and pressure applications. This type is also available in annealed rolls.
Type M is thinner than type L and is used in low pressure applications. It is available mostly in hard drawn straight sections.
Type DWV is the thinnest of all the copper tubings and is used in areas such as waste, vent, and drain applications. Just like type M, this type is available in hard drawn straight sections.
Nominal-Size Copper Tubing
This type of tubing is not used with HVAC refrigerants and may be seen as drains, water lines and minimal presssure applications. It is available hard and soft. The outer diameter(OD) is 1/8” larger than the inner diameter. All fittings must be the same as either the nominal or outer diameter. Fittings must not be cross-matched as leaks and loss of pressure will result.
Other Types of Tubing
There are other types of tubing besides copper. Aluminum, steel, stainless steel, and plastic tubing are used in HVAC and refrigeration applications. Aluminum coils and refrigerant piping are being used. The use of stainless steel may be seen in certain types of ducting and the walls of mechanical parts within an HVAC system. Plastic tubing or PVC has its advantages and disadvantages. It has certain heat restraints and metal fittings cannot be mixed with it. Advantages include versatility of use/application and corrosion is minimal.
Learning and becoming adept at flaring, connecting, bending, brazing, and soldering tubing in an HVACR system is one of the skills that must be mastered by any HVAC technician.