What is the maximum wall thickness of carbon steel pipe that must be used for Group A2, A3, B2, or B3 refrigerant liquid lines for sizes 1-1/2 inches and smaller?

The maximum wall thickness for carbon steel pipes used in refrigerant liquid lines for sizes 1-1/2 inches and smaller within Groups A2, A3, B2, or B3 is defined by the requirements set forth in the North Carolina Mechanical Code. Schedule 80 pipe is specified because it provides a thicker wall than Schedule 40, which is crucial for ensuring strength and durability under pressure, especially when dealing with refrigerants that may be more corrosive or require higher working pressures.

Thicker wall pipes, like Schedule 80, help ensure that the system can withstand potential pressure fluctuations and stress without risk of failure. Schedule 40, while common for various plumbing applications, does not offer the same level of strength as Schedule 80 for this specific use case. Options such as Schedule 20 and Schedule 10 do not provide adequate thickness for the durability and safety standards that are required for refrigerant lines in these groups. Consequently, Schedule 80 is the most suitable choice for ensuring the reliability and safety of the refrigerant distribution system in compliance with code requirements.