Duct Connector: how to prevent it from creating a system?

[HVAC-Novice]

for the existing conditions I have the attached louver. It will have NO actual function for airflow. It is only there to look like an existing louver and I added a duct connector to model existing duct. That louver will be placed in existing phase For new construction I have different families and place them in " new construction"  phase. 

The problem is, the duct connector creates a system and I get this warning:

To resolve this warning, I delete the system it created and all seems fine. 

I guess I have a workaround and hope it doesn't create problems with new (actually useful) systems (I'm not that far yet to actually know). 

I tried multiple options for that connector (made it a fitting, forced flow to 0, tried global or other flow and so on). It always creates a system (and the warning). I also capped the duct. Is there a way to make the duct connector " dumb" enough to not create a system, but still allow duct drawing? 

My only other option is to not use a duct connectors and free-hand model the duct... but the duct connector really is nice for existing systems. 

My goal here is to effectively model the existing system, but also to not have warnings and issues that may or may not cause performance or other issues. 

[iainsavage]

Are you retaining the existing louvre in New Construction?

Are you retaining the existing ducts in New Construction?

Or will they be removed (on site I mean, not in your model)?

[HVAC-Novice]

For this project, a few will just stay in and keep functioning. Some will be replaced with anew one. Even if we abandon louvers, we sometimes leave them in place and have them blanked off. So, it could be any scenario depending on project scope. 

[iainsavage]

I don't think you can prevent it from creating a system.

Prior to 2023 you could have demolished it in the New Construction phase then (if you wanted) undemolished it and it would have been disconnected with an undefined system.

2023 onwards you can still do that but there's an extra step required to remove the system. Part 24 of this post:

https://forums.autodesk.com/t5/revit-mep-forum/revit-2023-demolition-problem/td-p/11217338/page/2

[HVAC-Novice]

Thanks, I'll keep that in mind once I get to demolition. At this point I'm not sure what will stay get abandoned, or demolished.

One issue with that is, resolving anything in demolition, still means I have the warnings while building the existing model. And I wanted to consequently fight warnings as they appear (and not at some later time). For now I will settle for manually deleting the system it creates. 

I noticed the system (and warning) don't happen before I draw the first duct. So, this may be more a duct and not a Louver (duct connector) problem? 

[hmunsell]

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@HVAC-Novice wrote:

"...It will have NO actual function for airflow. It is only there to look like an existing louver and I added a duct connector to model existing duct. "

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I don't have 2024 yet, so i can't test your louver family, but what would happen if you did what the warning says.... if that louver and the connected duct is only there for appearance, have you tried setting the louver connector to Calculated? May not be what you would want to do in the real world, but if this is only for appearance then why not. 

[HVAC-Novice]

I tried calculated, preset, in/out/bi-directional, global, supply.... tried it as fitting... I'm sure there is a combination I haven't tested. but none really seem to make a difference. 

On my " regulars" louvers i have them calculate based on flow coming in/out. but for demolition I don't plan to connect those ducts to an actual device with a duct connector. an existing AHU, for example, will just be a dumb rectangular " Mechanical equipment" (attached)  and the duct will just be " free hand routed to look like it is connected". So there won't be a proper system or flow. 

Technically I didn't need the louver duct connector... it just makes drawing ducts easier. Existing drawings give me the elevations with louver location and size, and from there is it relatively easy to get a somewhat accurate existing duct system. 

[iainsavage]

Do you want to calculate flow in the existing system? If not then you can ignore the warning.

I would normally have the louvre connector as Calculated.

The sequence is usually:-

• air terminals are Preset and pass flow up to fan/AHU
• roomside connector on fan/AHU is Calculated and reads total flow from all air terminals.
• parameters and formula in fan/AHU pass flowrate to Preset connector on atmospheric side
• Calculated connector on louvre reads flow from atmospheric side of fan/AHU.

[HVAC-Novice]

I don't want to calculate any existing flow. My old "self" would just ignore the warnings.

But I started to consequently squash warnings as they appear to (hopefully) have zero warnings and hopefully a better model and modeling practice.

And if I have all those warnings I could ignore, that will blind me to other warnings. 

[iainsavage]

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@HVAC-Novice  wrote:

I don't want to calculate any existing flow. My old "self" would just ignore the warnings.

But I started to consequently squash warnings as they appear to (hopefully) have zero warnings and hopefully a better model and modeling practice.

And if I have all those warnings I could ignore, that will blind me to other warnings. 

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Then you need to sort out the configuration of the systems to make them properly connected. 

Example of supply system including outside air system:

Reverse the In/Out directions for Return/Exhaust.

[HVAC-Novice]

My "existing"  mechanical equipment doesn't have connectors. It is just a box I can flex to make look like an AHU, radiator or other mechanical device.  This is to keep it simple for items that either get demo'd or stay in place (but won't really have a function in the project... it is just a place holder or context so I don't build something lese there). 

For new systems that are the scope of the project, yes, all flows will work properly. 

[iainsavage]

Okay but you're still going to get the warnings for your existing systems.

If you can't live with the warnings then you need to connect the systems properly.

I just checked in 2023 and even if you split and divide the system, then delete the sub-system so that it becomes undefined, the components still retain their connections but the  warnings seem to be suppressed so that's also an option.

[iainsavage]

....but going back to your original question, I'm pretty sure that you can't force a connector to not connect to/create a system when you connect a duct to it.

[HVAC-Novice]

Deleting the system in system browser resolves the issue. The system is created once I add duct to the connector. 

ideally I find a way not auto-create a system when drawing a duct. but manually deleting the system is the second-best option. Maybe that is what it is for now. 

For existing systems I really don't want to make a "working" system since I want to keep those as simple as possible. Those just have to look like systems. i know it goes a bit against the Revit and BIM idea, but here the contractor only needs to see they have to demo an AHU that look's like a box. that generic family I attached above basically gets stretched to be an AHU, radiator, fan, VAV and whatever. 

[iainsavage]

Just to be clear I was only offering my suggestions because I offered "Do you want to calculate flow in the existing system? If not then you can ignore the warning." and you responded "My old "self" would just ignore the warnings.

But I started to consequently squash warnings as they appear to (hopefully) have zero warnings and hopefully a better model and modeling practice.

And if I have all those warnings I could ignore, that will blind me to other warnings."

So I assume you have now put that principle aside and accept that you will have warnings for your existing systems which you will now just ignore?

[HVAC-Novice]

I leave the last error since Revit seems to have a bug. 

I completed all my existing equipment and ducts so far. More warnings appeared:

- It told me can't calculate the flow in fitting: resolved by selecting all fittings and setting calculation to "none"

- It told me I have open connectors from louvers that have no ductwork. I couldn't just "cap" a louver. i copied my louver family and deleted the connector out of that family. I used that for the louvers with no duct and all open duct connector warnings were gone. I also capped all open ducts.

- I deleted all BUT ONE systems in system browser and that eliminated all those warnings

Why did I leave one warning? Here comes the bug. When I delete that last warning, the "Warning" button (under Manage) stops working. it won't open up the warnings dialog. I opened a different project in the same session, and there the warning still works (so, it isn't my Revit screwed up). I then restored a backup. All is fine if I leave this one system in place and warnings work. but if I delete that system, the warning button stops working (no, it isn't grayed out like when there are no warnings, it is bright yellow, just doesn't do anything). I tried many times (and then used "undo"). 

And yes, the connector in the louver is set to "calculated". That warning seems wrong. 

Edit: maybe it isn't a bug at all. Or the bug is just that the "Warning" symbol doesn't gray out. this is what it looks like after deleting the last system and there should be no more warnings. It is yellow, not gray as it should

but if I add another louver with connector (and that creates an open connector error), the warning button works again and only shows that new error. 

This makes me think the bug is the button not graying out. If this holds true and I can delete that last system, that means I can have zero warnings. 

[RobDraw]

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@HVAC-Novice wrote:

I leave the last error since Revit seems to have a bug. 

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The problem with this is that "bug" is Revit doing what it is supposed to do. 

Here's my take on this. You leave it if you want.

I think the problem is your use of the content. I would recommend not using connectors for your existing systems if you aren't going to build complete systems. Fabrication parts, which don't use systems, might be perfect for your workflow. It would prevent any systems from being created for that content. There are other possibilities that could also work.

[HVAC-Novice]

I'll try that. Haven't done nay fabrication yet (since I don't fabricate).

Apparently thee is a "services" tab that allows to load services (I don't seem to have any loaded). But I googled and looked, and can't see such tab. Where do I find that or how does it look like? 

[RobDraw]

I've only dabbled in learning about setting up the data base but a service is kind of a dummy system when it comes to any data for the air. It's just a name for use in physically building the stuff. You just need one service that contains all of the fittings that you need. 

[iainsavage]

Have you installed Fabrication CADmep? It should be included in your subscription package. You need that to be installed before you can use fabrication parts.