For proper leak detection in HVAC-R systems, what should be combined with refrigerant during pressurization?

• A. Water
• B. Vacuum oil
• C. Inert gas
• D. Dry air

Answer: (C)

In HVAC-R systems, using an inert gas during pressurization for leak detection is the most effective method. Inert gases, such as nitrogen, do not react with refrigerants and create a safe environment for testing. When pressurized with an inert gas, technicians can identify leaks by monitoring the pressure drop over time. If there is a leak, the pressure will decrease, indicating where the refrigerant is escaping.

This method is advantageous because inert gases are non-flammable, non-toxic, and also do not contribute to any chemical reactions that could affect the system. They also have a low cost and are readily available. Using this approach allows for a clear and accurate diagnosis of leaks without introducing moisture or contaminants into the refrigerant system, which could affect its performance.

Other choices, such as water, vacuum oil, or dry air, are not suitable for this purpose. Water can cause corrosion and introduce contaminants. Vacuum oil might leave residues that could interfere with the refrigerant and the system's operation. Dry air, while not as harmful, can still contribute moisture, which could lead to issues in the system, particularly with refrigerants that are sensitive to moisture.