Hello Everybody,

I have a question regarding DuctRectangular.ByLines node. For unknown reason, it allways freezes when used. Here, for example, I am trying to model one simple segment of Duct with following inputs. According to my research, those should be correct. Do any of you know what may be the cause? Sorry, I cant post the file as it would require company permission.

Solutions decribed here does not help in my case:

thank you very much!

All Elements of DuctType and All Elements of MechanicalSystemType should return DuctType and MechanicalSystemType objects respectively. No idea why you’re getting generic ElementType objects.

@Nick_Boyts Thank you very much for your reply. Would it be possible for you to share the Revit and Dynamo file that you used for making this screenshot? I would like to compare it with my files and see where this error is coming from. So far I cant tell :).


Honestly, I spent whole morning trying to find what may cause this issue and so far no luck. I found this post, where the same ElementType data is beeing produced by the same components - Duct Creation Error - #8 by lfaussK8Q8Y. At apparently, it is working at the end.

Couldnt this be an issue of Dynamo version or something similar?

You should be able to replicate this with the OOTB template and types. This is the intended behavior.

Can you confirm:

  1. you’re looking at a project document.
  2. you’re using only the OOTB nodes (for the element types portion).
  3. the Revit version.
  4. the Dynamo version.

Can you also post a new image with the node previews of those 6 nodes turned on so we can see what each one is returning?

Hi, regarding your points:

  1. yes, 100%
  2. yes, Element Types → All Elements of Type → List.FirstItem are OOTB Nodes
  3. 2022.1
  4. 2.12 (Up-to-date according to the Dynamo itself)

here is the screenshot:

I messaged Taco Pover (inventor of the MEPover package) and he said that ElementType data is correct data type in current Revit version and should not be causing any issue.
After that I was experimenting with the script a little and I think that the issue might be in “Lines” input. I will upload the files for you to see. There are two “sources” i tried:

(1) Lines generated by Dynamo according to the imported models in the file - this will cause Dynamo to freeze when used
(2) Referenced Model line from Revit work space - this will cause the DuctRectangular.ByLines to output a null value

remodelling ducts_v2.dyn (130.7 KB)
simplified model.rvt (6.0 MB)

So non of these options works for me. Do you think you could have a look on my files?
Many thanks

Hello @acXBWH8 …you need element curve after your selection…

Lines generated in Dynamo works fine as well, could you show what listfirstitem in your first image give you…

Yup. I always forget about the change to ElementType. @sovitek has pointed out the curve issues. It’s hard to say what’s going on at each step without you showing everything all at once, but it looks like you used a dynamo curve the first time. Are you running in Automatic or Manual? Automatic can have issues creating elements and updating, sometimes causing an infinite loop. Make sure you’re running in Manual.

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Thanks, thats it! If I use the Manual mode and just press Run, it works. Very strange solution.

Thank you very much for your help!

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