How do ACR and nominal tubing diameters differ?

The distinction between nominal tubing and ACR (Air Conditioning and Refrigeration) tubing centers on how their sizes are defined. Nominal tubing is measured by its inside diameter (ID), which reflects the actual space available for fluid flow within the tube. This measurement is important for ensuring that the piping can accommodate the necessary flow rate for HVAC systems.

In contrast, ACR tubing is defined by its outside diameter (OD). This specification is crucial for applications where the outside dimensions need to match fittings, insulation, or other connected components. The ACR size can also relate to the tubing's wall thickness, which can affect thermal conductivity and pressure ratings.

Understanding these definitions is essential for HVAC technicians, as using the correct size tubing affects system performance and efficiency. Knowing how to distinguish between these measurement types ensures proper installation and optimization of HVAC systems.