Question: How does having a list of ducts with their flows help a client's engineering department? What is it that they are checking?
Answer: Here in Brazil, we have certain technical standards for flow and noise that are verified by these engineering departments and our business customers like to check these parameters. If any flow is outside the norm can cause liability lawsuits against the company. So in my company we maintain this standard to let the customers satisfied. We pay dearly for Revit and so I make it clear that it was a setback for us.
Don't we all love a good robust discussion!!
I understand there needs to be justification for bringing these back too and in what form.
From the current thread i would say that the users would like to be able to:
"The only way that you could populate a 'maximum flow' parameter on a duct element would be to use code (via the API) to dynamically ... update such a parameter by extracting the values from each connector, and finding the largest."
Could you give us a few details about how this could be done, or at least point us to some tutorials so that we can learn how to add that 'maximum flow' parameter using the API?
I work for an MEP consultant firm, and we recently began our first 2013 project. Like others here, I too was greatly annoyed to discover this 'multiple values' issue in duct segments with taps connected. I understand why this was done, but it doesn't seem like Autodesk thought through the implications of this change. Regardless of whatever functionality was added, the fact remains that in 2012 I was able to select a duct with taps and see it's total flow, and with 2013 I can't.
I want to learn how to add this duct parameer using the API, and if I'm successful, I'll post the solution here.
In my case I use these values in schematic diagram.
Version 2014 was already released but the issue is still there. When do you think we can have a solution to this? In the meantime, can you give us a "link" on how to extract this values.
Unfortunately, I can't comment on when I think this functionality will be improved, however, here is a sample code snippet that will look at all connectors on the duct, and find the maximum flow.... you can run this in the macro editor to verify. There are samples in the RevitSDK.exe (on your install dvd/image) for how to create parameters... so with that, and this example, one could concivably come up with a tool to automate the process of populating the duct with a parameter/value.
public void MaxFlow()
UIDocument uidoc = this.ActiveUIDocument;
SelElementSet sel = uidoc.Selection.Elements;
foreach (Element e in sel)
Autodesk.Revit.DB.Mechanical.Duct d = (Autodesk.Revit.DB.Mechanical.Duct)e;
double flow = 0;
foreach(Connector c in d.ConnectorManager.Connectors)
flow = c.Flow;
Units u = uidoc.Document.GetUnits();
string result = UnitFormatUtils.FormatValueToString(u, UnitType.UT_HVAC_Airflow, flow, false, false);
I've noticed in this thread you have repeatedly asked why. Please allow me to walk you through a typical scenario I might encounter on a project:
I have an air handler feeding 50 terminal units. I've done the original design and sized my ductwork according to my design standards, but later on in the project something changes and I need to add 5 more terminal units on the job and I need to adjust the airflow of 15 of those initial 50 boxes. I'm interested to find out how that additional airflow impacts my supply mains. In 2012 I needed only to click on the section of duct in question and it would tell me all of the characteristics of that duct i wanted to know, and if necessary I could resize.
In 2013, under the same scenario it seems your options are limited. One would seemingly have to find each terminal unit on the main and add them up manually. If there are a lot of terminal units downstream of the duct in question, this could be a very tedious process, adding lots of time and possible human error to a process that was instantaneous in 2012.
So far, the only work around i've come up with I believe has been suggested in this thread and others (or some variation). Basically i just need to create a section of ductwork upstream of a tap that does not have any taps associated with it. If would seem that if a section of ductwork has no taps, it can tell you the total airflow on the duct. So, if I put an elbow on the duct upstream of the tap, I can take that untapped section of duct to learn the airflow characteristics at that point. It's an added couple of steps, and might not always be an option but it works in a pinch.
Just thought I'd share.
For those of you who are desperate to check the duct properties at any point of the duct length, you can add 2 split element in between duct branches or 1 if there is a transition (please see attached screenshot).
Hi Eric-- thanks for shaing.
>> I've noticed in this thread you have repeatedly asked why.
yes, it helps make sure we hit all potential use cases... for example, in your explaination, you said nothing about being able to tag.. but others have in this forum and elsewhere.
>> I'm interested to find out how that additional airflow impacts my supply mains.
Is this 'impact' actually directly to the Flow parameter? Or, is it indirectly in terms of the resulting velocity or friction (loss per length)?
I guess i'm not sure what you mean when you say "is this impact actually directly to the flow parameter? or is it indirectly in terms of the resulting velocity or friction" so i'll put it this way:
Right, wrong or indifferent - when I size my ductwork i try to make sure that at any given point on the system my ductwork does not have a pressure drop per 100' in excess of a certain value - for example, 0.20 inches per 100'. I understand that while the section of duct in question may only be 10 feet long and thus won't necessarily cause a huge impact on the system, I consider it best practice to not knowingly design my ductwork for a pressure drop above a 0.20 even if it is only for a few feet.
It's a nice check to be able to select a piece of ductwork at any point on the system and know what kind of airflow, velocity, pressure drop, etc. that I have in the system at that time. Maybe it's because I want to design for future capacity, maybe it's because I have space constraints and I want to know how severe the conditions will be at that point because I cannot upsize my ductwork or reduce the airflow. These are all common issues I encounter on projects. Yes, we do look at the system as a sum of it's parts, in which case the system analyzer is good, but it's also nice to have a convenient way of checking your design at making adjustments while getting instantaneous updated information.
Hi Eric.. what you've described is exactly what I mean by 'indirect'... you're not really interested in the Flow itself, you're interested in the pressure drop that is computed from the flow. To help with the workflow you've described, you can use the System Color Scheme to give you immediate visual feedback as you work... for example, configure the Color Scheme to color ducts with friction above 0.20 red, and eveything else green. This way, you can quickly find friction issues as you work, and not even have to select a duct to see the values. You specify the criteria, and it helps you meet them, with out having to pick ducts one by one and look over to the correct location in the Properties Palette.
See attached image for example.
I understand the desire to see more of the flow related parameters when a duct is selected, however. We have this in our backlog for future consideration.
Log into access your profile, ask and answer questions, share ideas and more. Haven't signed up yet? Register
Start with some of our most frequented solutions to get help installing your software.