Ductwork and System Inspector

[nathanMB9D4]

I have attached a simple mechanical system I am attempting to do (version 2025).  When I connect the return duct to the equipment, all of the airflows go completely haywire.  Sometimes Revit makes up random numbers, sometimes it shows the airflow everywhere as zero.  I have tried "troubleshooting" (I.E.  Deleting and redrawing everything, one component at a time), but still cannot figure out why this is failing.  I've used the same components and procedures in other systems and eventually got them working, but not this one.  Any ideas?

[iainsavage]

Initially you have this error message.

This is caused by a disconnection at the equipment:

Once this is corrected the error message clears, however the flows still don't work and the system inspector shows flow reversals in the system. This is usually a symptom of flow mis-directions causing Revit to get confused.

When I disconnect your ducts from the equipment the flows work okay.

So I can't fully explain this behaviour (yet) but it seems to be related to the mechanical equipment (and you need to fix that disconnection that I mentioned at the beginning).

[iainsavage]

Interestingly the systems work okay when upgraded to 2025:

There have been some issues with how systems behave in 2024 so make sure you have the most up-to-date version of 2024 because there have been a few updates and hot fixes.

Current version should be 2024.3.1

https://www.autodesk.com/support/technical/article/caas/tsarticles/ts/1BlfQlbA9wWd1JmijceW6d.html

I'm not on that version yet, I've got 2024.2, but since I'm no longer on subscription I can't always get the most up-to-date version.

Try updating.