Hello, sorry for my english but I'm italian.
I have a problem with the calculation of pressure drop in fittings.
The loss coefficient is equal to zero using the ASHRAE tables.
How to obtain pressure loss in fittings?
I have the same problem, but as i know the developer's of Revit, they cannot answer your question.
Its' really disturbing and boring, that i have to check the forums all the time, if have a problem. It needs more time, that i can spend on work.