I often encounter this problem with the REVIT duct fitting loss calculation. Only now have I time to try and relay it (using Revit 2024). In the attached PDF I have summarized the extent of the problem with some screen grabs, calculations and tables.
THE PROBLEM: Revit does not seem to calculate correctly the pressure losses of a simple T-piece. For the specific fitting that I used, very simple, Revit should revert to the SR5-5 table, but by default it goes to the SR5-1 table, no problem and even though I shouldn't, I edit the loss calculation method and change it to SR5-5. I pull up the very same table that Revit supposedly uses for the calcs (C:\Program Files (x86)\Common Files\Autodesk Shared\Revit Shared\Ashrae) and do the calc by hand and find the branch loss coef. to be 6,31. Sounds about right, it is a terrible take-off. Now, when I look at Revit's calc. it does not even come close. I get 0Pa losses on the branch and and error loss (as if the coeff. value fell outside of the table's data), -93952.19 Pa.
Can anyone form Revit's MEP department please explain why this is happening. Considering what Revit costs, it should be as close to error proof as possible.....
