Retrieving correct pressure loss coefficient for Bullhead tee

[CRampley]

Is there any way to design taps off of a capped main (example picture attached) that results in Revit's algorithms identifying it as ahsrae fitting SR5-15 for the purposes of pressure drop calculations? It currently seems to select either SR5-11 or even SR5-1 in some instances, bizarrely. 

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[iainsavage]

Its not your exact situation but in this post @Martin__Schmid explains how Revit analyses fittings to determine the appropriate tables to use.

https://forums.autodesk.com/t5/revit-mep-forum/duct-fitting-amp-ashrae-table/m-p/10943304#M84281

Not sure if this will help you on how to dimension your fittings to meet the criteria for the fitting that you want.

You could maybe also create the fitting as one fitting family and you can then define a loss coefficient for each connector. @HVAC-Novice can maybe advise on that.

[HVAC-Novice]

check out this thread

https://forums.autodesk.com/t5/revit-mep-forum/revit-2022-duct-fitting-pressuredrop-how-to-manipulat...

Forget about those ASHRAE tables. They are more than questionable and don't include fittings I see every day in actual installations. I ended up with system where a 45° elbow had a higher pressure drop than a 90°. Or they don't have the different R/D data. I just gave up on that. 

I used the SMACNA fittings and created my own formulas to calculate the pressure drop. If SMACNA doesn't have a fitting (or the wrong flow direction, many coefficients are direction dependent in the very same fitting), pick a CONSERVATIVE example of a similar fitting. That way you also can assign pressure drop to each leg of a fitting. 

[handjonathan]

Hi @CRampley 

Thanks a lot for posting your question to the forums!   Have the solutions suggested by @iainsavage @HVAC-Novice helped with your issue?
 
We look forward to hearing back from you with more information so we can help you as a community!