NATE Air Conditioning and Heat Pumps Practice Exam

Which of the following should be used to leak-test refrigerant tubing?

1. Compressed air

2. Dry nitrogen

3. Oxygen

4. Water

The correct answer is: Dry nitrogen

Using dry nitrogen to leak-test refrigerant tubing is the correct approach due to several important factors. First, dry nitrogen is an inert gas, meaning it will not react chemically with the materials typically used in refrigerant systems, such as copper or aluminum tubing, or the refrigerants themselves. This characteristic prevents potential contamination or reactive problems that could occur if other gases were used. Additionally, dry nitrogen is dehydrated (moisture-free), which helps to avoid introducing any water vapor into the system. Water vapor can lead to issues like corrosion and acid formation within the refrigerant lines, especially when it interacts with any remaining refrigerant or oils. Furthermore, dry nitrogen can be charged at higher pressures to help identify and locate leaks effectively. When the gas is pressurized within the tubing, any small leaks will produce a noticeable drop in pressure, allowing technicians to pinpoint the areas where refrigerant is escaping. In summary, dry nitrogen is safe, effective, and helps maintain the integrity of the refrigerant system while facilitating a thorough leak test.