The Conduit Nominal Diameters node (the sheet in the Conduit.xls workbook) defines what nominal conduit diameters (NCD) are valid for the different conduit materials classes. These NCDs appear on the New Conduit Run Dialog in the Nominal Conduit Diameter box.
NPD
Type the nominal conduit diameter that you want available for the conduit materials class.
NPD Unit Type
Specify the units for the nominal conduit diameter value that you entered in the NPD column. For example, type mm or in.
Spec Name
Type the name of the conduit specification (materials class) for which you are defining valid nominal diameters. The specification that you enter must be defined on the Conduit Specifications.