A minimum evacuation level for an air conditioning system is:

• A. 1,000 microns
• B. 500 microns
• C. 100 microns
• D. 5,000 microns

Answer: (B)

During evacuation, you’re removing air and moisture from the air conditioning system to prevent moisture-related problems and ensure a proper refrigerant charge. The level is measured in microns of mercury with a micron gauge. A minimum evacuation around 500 microns is typically required to effectively remove moisture and non-condensables. Shallow levels like 1,000 microns can leave moisture behind; deeper vacuums such as 100 microns aren’t usually necessary for this purpose and take longer to achieve; and a vacuum of 5,000 microns is too shallow to ensure the system is free of moisture and air. Therefore, 500 microns is the standard minimum evacuation level.