Isogen : Pipe diameter error

[JohnKimTW]

I have route a 4" pipe. When i generate a iso using isogen, the pipe size is written as 2581NS. Thats like (4"x25.4x25.4). It seems like the pipe size was converted to MM and then try to convert it again. I wish to remain the pipe size in imperial unit since direct conversion does not result in DN. Would appreciate if someone can enlighten me on how to solve this issue.

[MMSW]

What type of units have you defined for your project ?
You are able to define units when you create a new project, imperial size and dimensions / metric size and dimensions / imperial sizes and metric dimensions. I doubt the last option works.
If you use ASME catalog in Metric project you will get a direct conversion and will end up in nominal sizes like 102, 203,.... to have nominal sizes like 100, 200 shown on ISOs you should use DIN catalog.
Generally there is a bug in this version of P3D regarding imperial/metric units.
http://discussion.autodesk.com/forums/thread.jspa?messageID=6263898鑚