We are finding in Revit 2014 that the duct pressure loss reports are consistently reading loss across taps as zero even though they are not, and even when every other piece of the system is reading correctly. The table lookup is set, it is just not reading the correct value from the ASHRAE table. Here is a screenshot.
I would be happy to send additional files. Really looking for confirmation on this one. We are using standard OTB fittings. This only happens with taps.
Regards
Alan Jackson
CASE
Solved! Go to Solution.
Solved by Martin__Schmid. Go to Solution.
To shed a little insight, foundationally, the issue is that the way Revit keeps track of pressure loss. It does so by assigning a loss at each connector. In the image below, there are two paths through the tee. The losses are accounted by assigning a loss at Connector A and B.
For the tap condition, the physics are basically the same… there is a loss through the branch path D and the path E, but there is nowhere for Revit to store the data related to the loss along the main, since there is no connector.
I realize you don’t really care about that.. you just want it fixed. We understand the problem, but it hasn’t been a priority relative to other things. This does come up periodically, however, when looking across the spectrum, lists such as AUGI’s, and speaking to business leaders in MEP firms, we see that there are bigger issues that impact more users.
We do keep this on our list for consideration, so your voice is being heard. Thanks for posting.
tlees90 - you're right, there have been ongoing improvements to the calculations related to tapped sections, including improved formulae, improved sections, improved color fill, improved tags, etc.... which has probably gotten us closer to solving the branch and main drop at the junction, but we aren't there yet.
Martin
I understand it doesn't work. I guess I am a bit disappointed in you response though. I speak to business leaders at many MEP firms and calculations and analysis and the shortfalls or lack of capability that exists in the platform in this area is a huge issue that comes up repeatedly. Perhaps we should exchange notes.
I think it is very telling that the platform is even in a state where fixing calculations fall into a list of things "to be considered". It is a mindset like this that is the reason why the platform is continually being used only for coordination and documentation among MEP firms and nothing more, despite how the product is being marketed.
I am sorry if this message comes across a bit cynical, but I think we have known each other long enough that you understand I have high expectations.
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Alan Jackson
CASE
Martin,
If voices is what is needed in order for calculations and analysis to be prioritized, I would like to add mine.
Menwhile the platform should not be advertised to engineering practices as nothing more than a model based documentation tool.
Regards,
Silviu Petrea, R.A.
AEI | AFFILIATED ENGINEERS, INC.
So I've just recently stumbled upon this problem when my current firm decided to possibly use the software for critical path analysis. Seeing as how this was posted in 2014 I was wondering if a solution had been discovered or not.
I put this issue on the ideas forum.
Please vote it up!
https://forums.autodesk.com/t5/revit-ideas/pressure-loss-through-tap-always-zero/idi-p/8897291
Hi,
What happened with this problem?
Almost 10 years have passed...
Time flies...
BR
Ljuban
Apparently it moved over to the IDEAS forum where it's more appropriate. You can also try the Product Feedback page.
We added the capability to assign a table to a tap.
The confusion value "0" might appear, but the value is assigned to the downstream segment in Supply.
Hi, Ljuban
Please refer to this post which Kevin mentioned in this thread.
https://forums.autodesk.com/t5/revit-ideas/pressure-loss-through-tap-always-zero/idi-p/8897291
It's in there since Revit2017