During a system evacuation, which gauges should be opened?

During a system evacuation, opening both the high-side and low-side gauges is essential for effectively removing moisture and non-condensable gases from the refrigeration system. Evacuation requires that the entire system be brought to a deep vacuum to ensure that all contaminants are eliminated.

By opening both gauges, the evacuation process allows the vacuum pump to remove air, moisture, and impurities from the entire refrigerant circuit, including both the evaporator and condenser sides of the system. This comprehensive approach helps to ensure that there are no pockets of air or contaminants left in the system, which could lead to inefficiencies or potential damage once the system is recharged with refrigerant.

The other options imply an incomplete evacuation process. Opening only the high-side or only the low-side limits access to only part of the system, which could result in an inadequate evacuation. Not opening either gauge would not facilitate the evacuation process at all, leaving the system susceptible to moisture and air contamination.