NATE Air Conditioning and Heat Pumps Practice Exam

When performing a vacuum, ensuring that all service valves are closed is essential because closed valves prevent air and moisture from entering the system during the evacuation process. If any service valve is left open, it can compromise the vacuum by allowing contaminants or vapors to enter, which reduces the effectiveness of the vacuum and can lead to potential system issues down the line.

Utilizing a proper vacuum technique is crucial for maintaining the quality and safety of the refrigeration system, as moisture and air can negatively affect the performance and longevity of the equipment. Ensuring that all service valves are closed creates a sealed environment necessary for achieving a proper vacuum. This control allows the vacuum pump to efficiently remove air and moisture from the system without interference.