ESCO Air Conditioning Practice Exam

Back seating a two-way service valve effectively closes the service port while preventing any system flow. This operation is typically performed to isolate the service port while allowing the refrigerant to continue circulating through the system itself. When the valve is back-seated, it means that the valve's main seal is engaged, which prevents any refrigerant from escaping through the service port.

This is particularly useful when technicians need to connect or disconnect service equipment without interrupting the system's operation or causing refrigerant loss. It ensures that the service area is securely sealed off, maintaining system integrity while still allowing normal operation elsewhere in the air conditioning system.

The other options reflect various states of service port flow that do not accurately describe the conditions that occur when the valve is back-seated.