Final answer:
Technicians must evacuate an appliance containing less than 200 pounds of R-22 to 4 inches of mercury vacuum before a major repair, as per EPA regulations to minimize environmental impact.
Step-by-step explanation:
The question is regarding the standards for the evacuation of R-22 refrigerant before performing a major repair on an appliance. Specifically, for appliances containing less than 200 pounds of R-22 and using recovery and recycling equipment manufactured after November 15, 1993, the Environmental Protection Agency (EPA) requires that the refrigerant be evacuated to 4 inches of mercury vacuum. This standard ensures that the refrigerant system is sufficiently emptied before opening it up for major repairs, to prevent the release of R-22, which is a hydrochlorofluorocarbon (HCFC) known to contribute to ozone depletion. The level of vacuum must be measured with the use of a suitable gauge to ensure compliance with regulations.
When using recovery and recycling equipment manufactured after November 15, 1993, technicians must evacuate an appliance containing less than 200 pounds of R-22 to a level of 10 inches of mercury vacuum (HgV) before making a major repair.