The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) publishes a database that includes loss coefficient tables for many duct fittings. Each duct fitting in the database is identified by a unique number. The external tool you use to analyze your system may require that all fittings in the system are assigned an ASHRAE fitting number.
You can assign ASHRAE identification numbers to duct fittings in a system either using the Properties palette or the Modify Fitting ID dialog box in the event log of the Duct System XML Export dialog box.
To specify an ID in the Properties palette
To specify an ID when exporting to duct system XML
If the ASHRAE number you want to use is in the list, select it for Assigned Engineering ID.
If the ASHRAE number you want is not in the list, or there are no numbers listed, enter the ASHRAE fitting number for Assigned Engineering ID.
This ID is assigned to the fitting in the drawing. Repeat as necessary to resolve all fitting ID warnings.
If desired, you can run the duct system export again to include the revised fitting IDs.