NATE Air Conditioning and Heat Pumps Practice Exam

What gas must be purged through a refrigerant circuit to prevent the formation of oxides whenever brazing is being done?

1. Any HFC

2. Dry nitrogen

3. Filtered air

4. Oxygen

The correct answer is: Dry nitrogen

When brazing in a refrigerant circuit, purging with dry nitrogen is critical to prevent the formation of oxides. During the process of heating, metals can react with oxygen in the air, leading to oxidation. Oxides can form on the surfaces being brazed, which can interfere with the integrity and quality of the joint. By using dry nitrogen to purge the circuit, you create an inert environment that displaces any oxygen present. This effectively reduces the possibility of oxidation during the brazing process. The use of dry nitrogen also helps to maintain system integrity and assists in preventing contamination from moisture, which is another critical factor in ensuring a successful brazing operation. This practice is widely accepted and considered standard in the HVAC industry to ensure reliable and durable connections within refrigerant lines.