Bob Pietrangelo wrote:
Refigeration tubing is ID, Plumbing pipe is sized by OD.

Bob,
Check your references. You have it backwards. Refrigeration tubing (ACR)
is sized by the actual OD. Plumbing & heating tubing is sized by the
nominal I.D. Therefore 1/2" plumbing tubing has an actual OD of 5/8". I
just checked my textbooks to verify this so as not to give dis-information.

Source: Refrigeration & Air Conditioning Technology, 3rd Edition, 1995,
page 99.