NATE Low Global Warming Potential (GWP) Practice Test

Removing moisture and air from the system and achieving the required vacuum before charging is the approach being tested. Purging with dry nitrogen to remove moisture and push out air sets up a dry, inert environment, minimizing the chance of moisture or reactive gases entering the system. After that purge, evacuating to the specified vacuum level removes remaining moisture, non-condensables, and contaminants, ensuring the internals are clean before introducing the low-GWP refrigerant. This sequence helps prevent moisture-related issues such as acid formation, oil degradation, and poor heat transfer, and it supports a proper refrigerant charge and performance. Purging with dry nitrogen alone lacks the vacuum step, purging with dry air can introduce oxygen and residual moisture, and purging with moisture-laden gas defeats the purpose of preparing a clean, dry system.