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Thread: Revit TAG is showing incorrect duct velocity when lining is used

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    Default Revit TAG is showing incorrect duct velocity when lining is used

    Hope this is a simple solution, when I apply a tag with the 'Velocity' parameter it shows the wrong figure.

    The internal calculations and the parameter values seem correct, just the tag displays the wrong info.

    The following two images (should) show the tag as it is displayed incorrectly in the file, and the actual parameters of the tag.

    Duct flow tag.bmpParameters.bmp

    Any idea on how to make the tag show this properly?

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    Revit Forum Manager Steve_Stafford's Avatar
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    Default Re: Revit TAG is showing incorrect duct velocity when lining is used

    Without digging in and testing myself... when lining is applied the clear size dimension of the duct is decreased by the thickness of the lining, not increased to maintain the clear size dimension(s). This might account for the change in flow. If you increase the size of the duct so the overall dimension accounts for the addition of the lining does the flow you expect appear again?

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    Default Re: Revit TAG is showing incorrect duct velocity when lining is used

    Thanks for your reply Steve,

    I have attached a new image showing the two ducts and the velocity reported. Unfortunately the Revit file cannot be attached as the forum does not allow enough space to do so.

    The duct at the top is unlined at 300x300 with a velocity of 5.6 m/s

    The lower duct is 25mm lined at 350x350 giving a free internal size of 300x300, the same as the duct at the top.
    The TAG on this reports the velocity at 4.1 m/s, so the tag is using the overall duct size and not the free size.
    However, if you click to edit the comment field it shows that the velocity is 5.56 m/s

    It looks like Revit is reporting the velocity incorrectly in the tag, but using the correct size for internal calculations.

    Only solution I can find so far is to manually note each duct, but this will cause a lot of extra work when duct sizes change.

    Any other ideas?

    Mike
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    Revit Forum Manager Steve_Stafford's Avatar
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    Default Re: Revit TAG is showing incorrect duct velocity when lining is used

    Looks like you may have trapped a reporting/calculation bug. I've passed on a link to this thread to a couple friends at Autodesk. It would help if you start a support request with them so you and your company can help take it further directly with developers, potentially.

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    Revit Forum Manager Steve_Stafford's Avatar
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    Default Re: Revit TAG is showing incorrect duct velocity when lining is used

    I got the following response:

    Quote Originally Posted by Autodesk Support
    ...My initial testing show that there is a problem when using Duct/Taps (I don’t see the issue when using Duct/Tees). I will file the issue to the MEP team to investigate. I will reply to the AUGI post in a while...

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    Default Re: Revit TAG is showing incorrect duct velocity when lining is used

    Thank you for the report. I can reproduce this issue when using Duct with Taps and lining is added. A problem report has been filed and we are investigating the issue.
    I am sorry for the inconvenience.

    Sincerely,
    Anna Oscarson
    QA Analyst
    Autodesk, Inc.

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    Revit Forum Manager Steve_Stafford's Avatar
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    Default Re: Revit TAG is showing incorrect duct velocity when lining is used

    Thanks for the follow up Anna, hopefully it can be addressed in a future web update.

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    Default Re: Revit TAG is showing incorrect duct velocity when lining is used

    Thank you Steve and Anna,

    I look forward to the future Revit update.

    In the meantime I will use a work around by placing a split in the duct before the tag, or after the tap.
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