Revit MEP

Revit MEP

Reply
Member
adamgraham
Posts: 3
Registered: ‎11-08-2010
Message 1 of 11 (1,971 Views)

"no loss defined" warning - Revit MEP 2010

1971 Views, 10 Replies
09-27-2011 08:17 AM

After updating our model to Revit 2012, we have over 20,000 warnings, including over 19,000 that say "no loss defined." I've always been told to keep your warnings to a minimum to improve performance, and the model is painfully slow after the upgrade. How do I get rid of these warnings?!?! I don't want Revit to calculate pressure drop, I just want the warnings to go away.

 

Even if I start a new project and create a simple system, I can't get rid of all of them. I draw a duct with an elbow: the warning appears for the elbow. The loss method is "Coefficient from table" but there are no options for the ASHRAE Table. When I connect the duct to a diffuser, the warning goes away, and the elbow now refers to the table "SR3-1." Now, at the other end of the duct I attach an Air Handler and make it the equipment for my system. The warning still appears: "no loss defined" for the Air Handler. 

 

How do I make these 20,000 warnings go away?!?!?! And don't tell me change each fitting to "coefficient" and manually set it to something. There are 20,000 of them, and more will be created as the project progresses. 

Product Support
Chris.Aquino
Posts: 413
Registered: ‎06-27-2010
Message 2 of 11 (1,956 Views)

Re: "no loss defined" warning - Revit MEP 2010

09-27-2011 04:05 PM in reply to: adamgraham

The two most common causes for the "No Loss Defined" warnings are fittings in certain conditions do not have loss information either from a table, or specified, and in the other case, there is no flow so there is no loss.


The only change that was made for 2012 was that the warning was included under the displayable warnings.

I would look at your fittings and make sure there is a loss associated.



Chris Aquino
Knowledge Domain Expert
Customer Service & Support
Autodesk, Inc.


The Revit Clinic
@Revitclinic
New Member
ScottVayo
Posts: 1
Registered: ‎08-16-2007
Message 3 of 11 (1,758 Views)

Re: "no loss defined" warning - Revit MEP 2010

12-02-2011 09:49 AM in reply to: adamgraham

I have just encountered this warning message in a Revit 2012 Architecture file.  Very strange.  There is a mechanical RVT linked into the Architectural model, but why would I see this warning in the Architectural model itself??  And more importantly, how do I get rid of it?

 

Any guidance is greatly appreciated.

 

Scott

Contributor
glenwalson7986
Posts: 11
Registered: ‎08-25-2009
Message 4 of 11 (1,543 Views)

Re: "no loss defined" warning - Revit MEP 2010

03-15-2012 09:30 AM in reply to: adamgraham

Chris, 

I'm getting this No Loss error as well. Even when I add flow to the duct system and create the needed system elements. The Loss coefficient still remain blank. It there a setting in a support file that maps Revit to the ASHRAE tables? 

 

Does this type of warning need to be fixed to help performance? 

 

If this doesn't work , then Revit is not performing any duct static pressure calc's correctly. Which is not very helpful. 

 

Any insight on this warning would be greatly appreciated.

 

Thanks, 

 

Glen W. 

Interface Engineering

Valued Mentor
julianjameson8403
Posts: 458
Registered: ‎06-16-2010
Message 5 of 11 (1,530 Views)

Re: "no loss defined" warning - Revit MEP 2010

03-16-2012 02:43 AM in reply to: glenwalson7986

As I understand it, when you create the system Revit parses through the XML file determine what loss coefficient based on the fitting type, the sizes and the flow rates. However any of the former items are outside the range of the Ashare tables then Revit return a zero value. You can however change the way Revit assigns a pressure drop by adding a specific co-efficient or a specific value. That should then remove the warning.

Also make sure that all equipment, and accessories have the ability to add pressure drops by mapping a parameter to the in-built pressure drop parameter.

Note that shoes/taps do not work briliantly in a system and tend to affect the calculations (Annoyingly)! Anyway - once you get the initial issues sorted, the systems tend not to be to far off manual calcs (not always mind but most of the time)

If my reply answers your query, please use the Accept as Solution.
Please give Kudos as appropriate to enhance the value of these forums.

Thank you!
Contributor
JColombe77
Posts: 23
Registered: ‎06-21-2011
Message 6 of 11 (1,427 Views)

Re: "no loss defined" warning - Revit MEP 2010

04-12-2012 09:34 AM in reply to: julianjameson8403

So I have flow before my fittings and afterwards.  I have the ASHRAE table add in.  But no pressure loss for any fittings therefore no system static pressure.  It does not seem to be loading the coefficeint from the table some fittings are identified by an ASHRAE code for example "SR3-1" is one of my elbows but no loss cooefficent.  I have the loss coefficeint set to "Coefficient from table".  Even if I change to "Coefficient" and put in a number like 0.5 I get nothing for pressure drop.

 

I am drawing in the existing phas.  when I check for disconnects it says my diffusers are not well connected but they are connected have flow and transmits flow to the duct it is connected to

 

PLEASE HELP

 

Thanks in Advance

Contributor
JColombe77
Posts: 23
Registered: ‎06-21-2011
Message 7 of 11 (1,425 Views)

Re: "no loss defined" warning - Revit MEP 2010

04-12-2012 09:41 AM in reply to: JColombe77

The weird thing is if I go into the family of my elbows for example and try to look for the pressure loss parameter it does not show there.

 

The only parameter I can even add is pressure not pressure drop

Contributor
JColombe77
Posts: 23
Registered: ‎06-21-2011
Message 8 of 11 (1,424 Views)

Re: "no loss defined" warning - Revit MEP 2010

04-12-2012 09:47 AM in reply to: JColombe77

Also it says duct system is not well connected and neither is my rooftop unit

Contributor
glenwalson7986
Posts: 11
Registered: ‎08-25-2009
Message 9 of 11 (1,419 Views)

Re: "no loss defined" warning - Revit MEP 2010

04-12-2012 10:12 AM in reply to: adamgraham

What seemed to shead some light on this for me was Revit 2013 and there static pressure calc. reports. When the fittings are set to assign the loss from the ASHRAE tables, it does, but it never showns the value in the parameter feild.

 

When you look at the reports from Revit 2013 you can see the actual value Revit uses from the ASHRAE Tables.

 

So, in the end it is working, but it shouldn't be generating the warning "No loss defined" because  there is one.

 

Glen

Spoiler
 

 

Contributor
JColombe77
Posts: 23
Registered: ‎06-21-2011
Message 10 of 11 (1,416 Views)

Re: "no loss defined" warning - Revit MEP 2010

04-12-2012 10:17 AM in reply to: glenwalson7986

When I check my system static pressure so something is messed up it says " Not computed"

Post to the Community

Have questions about Autodesk products? Ask the community.

New Post
Announcements
Do you have 60 seconds to spare? The Autodesk Community Team is revamping our site ranking system and we want your feedback! Please click here to launch the 5 question survey. As always your input is greatly appreciated.