How is ACR tube measured?

ACR (Air Conditioning and Refrigeration) tube is measured based on the outside diameter. This measurement method is standard practice within the industry, as it allows for a consistent understanding of the tube's dimensions, especially when dealing with fittings and connections. The outside diameter is critical for ensuring proper fitment in systems, where the connection to other components such as valves, compressors, and other piping systems must be made securely. By focusing on the outside diameter, technicians can accurately select fittings and ensure compatibility with established installation practices and industry standards.

The other methods of measurement, while relevant in different contexts, do not apply to ACR tubing specifically for this purpose. Measuring based on the inside diameter would not provide the necessary information for compatibility in typical applications. Similarly, nominal measurements do not give precise information required for connecting tubing in refrigeration systems. Pressure class pertains to the tube's ability to withstand certain pressures, but it does not relate to its dimensional measurement.