Which refrigerant liquid line group requires Schedule 80 carbon steel pipe in smaller sizes?

The correct choice involves understanding the classifications of refrigerants and the materials required for their respective systems. In this context, refrigerant Group A is considered less flammable, while Group B contains more flammable refrigerants. Specifically, within Group A, the subcategory A2 comprises refrigerants with a lower flammability risk but still necessitates some safety precautions due to their potential for flammability under certain conditions.

For refrigerant liquids in Group A2, using Schedule 80 carbon steel pipe is mandated in smaller sizes due to the need for increased structural integrity and resistance to pressure, which helps manage the fluid safely. In contrast, other groups such as Group A1, primarily with non-flammable refrigerants, do not have the same structural requirements and can utilize standard materials without the need for additional reinforcements like Schedule 80 piping.

Understanding the reasons behind these classifications and their respective safety protocols is crucial for ensuring compliance with current mechanical codes and for safe refrigerant handling in practical applications.