Diffuser airflows resetting to 0 when modifying ductwork.

[micphillips]

In our mechanical model, when I attempt to edit ductwork, all airflows for all diffusers and grilles reset to 0. I've attached 2 screenshots to demonstrate 1 instance of this issue. In this case, I'm trying to attach a cap to the end of an open exhaust duct. When I add the cap, all airflows reset to 0, including airflows for diffusers not even connected to that system. I've tried everything I can think of and nothing is working.

Here are a list of "some" of the things I've tried:

• Restarting Revit and my computer.
• Completely redrawing the exhaust ductwork in the area I'm trying to add the cap to.
• Splitting the duct branch between the open duct and main, adding a cap, then reconnecting the ductwork.
• Doing the same as above, but copying the cap, pasting in same place, then connecting the ductwork to it.
• Turning off ductwork calculations. This works, but after I do some work and turn calculations back on, all airflows reset at that point.
• Several other random things to attempt to get this to work and airflows reset everytime.

[iainsavage]

Upload your file please

[HVAC-Novice]

Is the connector on the diffuser set to "preset"?

[micphillips]

Yes it is.

[micphillips]

I've attached the file. Due to NDAs, I had to remove strip the file before upload.

[iainsavage]

I'm not seeing the zero flows. Diffusers appear to have correct values.

Check that you have all updates for 2024 because there were some problems with the initial release that has been corrected in updates.

I do note that you have some disconnects in your systems, mainly at VAV boxes - example:-

Warning messages are as follows and this will be due to the disconnects:-

[RLY_15]

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@iainsavage wrote:

I'm not seeing the zero flows. Diffusers appear to have correct values.

Check that you have all updates for 2024 because there were some problems with the initial release that has been corrected in updates.

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+1 this. It appears to be a 2024-specific issue with how air terminal tags were initially reporting the Flow Parameter. You could work on the system and watch the tag read something to the effect of 'Calculating' and then 0 out, even though inspecting the air terminal would reveal that the Flow Parameter is correctly defined as the Preset value. Had this happen three weeks ago on a non-updated workstation.

[iainsavage]

There was this post and a couple of other similar ones but as far as I can tell updating the software has cured that issue.