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Pressure Loss through Tap always zero

14 REPLIES 14
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Message 1 of 15
alan.jackson
2701 Views, 14 Replies

Pressure Loss through Tap always zero

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.

 

Pressure_Loss_Report.png

 

Regards

 

Alan Jackson

CASE

14 REPLIES 14
Message 2 of 15

Welcome to our struggle. This has been a known issue for many years. I could go on and on about my frustration but it would just make me more angry. I have saved correspondence from Autodesk basically saying we know about it and don't have a plan to fix it, check back later.
Message 3 of 15

Ok. Well at least it is good to know it wasn't an issue on our end. It is unfortunate that Autodesk is not taking the concerns of the engineers who are trying to utilize BIM to its fullest capability seriously. Hopefully this gets resolved soon. Thanks for your reply.

Alan Jackson
CASE
Message 4 of 15

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.

 

Tee and Tap



Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.

Message 5 of 15

Is that really the case now though? You can see flows (and I believe static pressure) in between taps now so shouldn't the functionality to store different data between taps be there?
Message 6 of 15

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 Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.

Message 7 of 15

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.

 

Alan Jackson

CASE

Message 8 of 15

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.  

Message 9 of 15
mallen0080
in reply to: Martin__Schmid

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.

Message 10 of 15
Kevin.Thickett
in reply to: mallen0080

Message 11 of 15
LjubanL
in reply to: alan.jackson

Hi,

 

What happened with this problem?
Almost 10 years have passed...
Time flies...

 

BR

 

Ljuban

Message 12 of 15
RobDraw
in reply to: LjubanL

Apparently it moved over to the IDEAS forum where it's more appropriate. You can also try the Product Feedback page.


Rob

Drafting is a breeze and Revit doesn't always work the way you think it should.
Message 13 of 15

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.

Message 14 of 15
LjubanL
in reply to: tetsuya.hishida

Hi,

 

In which version of Revit we can check this?

 

BR

 

Ljuban

Message 15 of 15
tetsuya.hishida
in reply to: LjubanL

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

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