Why is nitrogen used when brazing in an R-410A refrigerant system?

Using nitrogen when brazing in an R-410A refrigerant system serves the important purpose of purging air from the lines. During the brazing process, high temperatures are used, which can cause oxidation and create scale within the refrigerant lines. When nitrogen is introduced, it acts as an inert gas that displaces air and moisture from the system, minimizing the chance of contamination. This is crucial because moisture and air in the refrigerant lines can lead to corrosion and chemical reactions that can damage the system, ultimately impairing its efficiency and functionality. Therefore, purging the lines with nitrogen helps ensure a clean, optimal environment for the refrigerant when the system is put into operation.

In this context, while nitrogen may have other effects like potentially helping with cooling or maintaining joint integrity, its primary role in this specific scenario is to prevent air and moisture from compromising the integrity of the refrigerant system during brazing.