Before making a major repair, to what vacuum level must technicians evacuate an appliance or component containing more than 200 pounds of R-410A?

To determine the appropriate vacuum level for evacuating an appliance or component containing more than 200 pounds of R-410A before making major repairs, it's crucial to understand the guidelines set forth by the EPA as well as the physical properties of the refrigerant.

The correct vacuum level for R-410A, which is a zeotropic refrigerant, is 10 inches of mercury (Hg). This level is necessary to ensure that all non-condensables, moisture, and always present air are removed effectively from the system. Achieving this vacuum level helps to prevent issues such as acid formation or freeze-up, which can occur when moisture is not adequately evacuated from the system.

While achieving a vacuum level lower than 10 inches of Hg may seem beneficial, in practice for R-410A systems, 10 inches is sufficient to ensure that the contaminants are removed while not overly stressing the components of the system. Therefore, evacuating to 10 inches of Hg is a standard and accepted practice before performing major repairs on systems with significant amounts of refrigerant such as R-410A.