Before making a major repair on an appliance with over 200 pounds of R-410A, to what level must it be evacuated?

To effectively make a major repair on an appliance containing over 200 pounds of R-410A, it is crucial to evacuate the system to the proper vacuum level to ensure that any moisture and contaminants are removed. The requirement for a vacuum level of 10 inches of Hg is based on industry guidelines, which aim to achieve a level of evacuation that significantly decreases the pressure within the system.

Achieving this level helps avoid potential issues, such as the introduction of moisture into the refrigerant circuit, which can lead to system inefficiencies or damage to components. By evacuating to 10 inches of Hg, the technician ensures that the system is adequately prepared for recharging with refrigerant, thereby maintaining efficient operation and prolonging the lifespan of the appliance.

Other vacuum levels listed do not meet the necessary standards for effective evacuation before a major repair, which is why they are not the preferred choice in this situation.