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Thread: Close-Coupling Families With Duct Connectors Sharing the Same Space

  1. #1
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    Question Close-Coupling Families With Duct Connectors Sharing the Same Space

    Hi guys,

    I produce AHU Revit models as part of my job but I have a query regarding how they get used by the clients.

    My AHUs are essentially glorified boxes and have the standard rectangular duct connectors on the ends.

    If I produce a separate ancillary, such as an attenuator and have duct connectors on the end of that too but that then gets pushed up against the AHU model in the project (effectively making two duct connectors share the same space) how does the user make sure the duct system is connected throughout the system when there is no space for ducting between the AHU and the attenuator?

    Pease see the image attached for a better idea of what I mean as I sure I'm babbling nonsense here.

    Sorry if this is a n00b question but I have virtually no training in the project building side of Revit, just family creation, so have always wondered this.

    Thanks very much.
    Attached Thumbnails Attached Thumbnails connectors.gif  

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    I would probably suggest nesting the attenuator into the primary AHU as Revit would require a transition duct between the two elements (however this could be handled with a very small piece of duct) but it will require a duct to connect the elements.

    Provide an option in the family with the attenuator or without in which case you may have to alter those families and provide an entirely new family with some connectors effectively removed. Would need some testing.

    I would need to test it out, but it may also be that the creation of the system allows it to happen and connects them, really would have to test the specific families in question.

    Basically what happens in the creation of the system is you choose the elements in the system, and then choose the Equipment it is connected to. At this point, there is no ducting created, and I can ask revit to propose layouts for me. I would be interested to see if the proposed layout shows errors. Usually it will show an orange line where there is an issue, this might be happening if the line to connect the attenuator to the AHU is too short for revit to actually place a duct. A simple solution might be displacing your connecter slightly in either family so that revit can place the duct.

    Anyhow before all of that you should really test it in a system and see if revit will play nicely with it but I have a hunch that it will produce an error and tell me it cant place a duct that short.

    What happens in reality? Is there a sliver of a duct placed to connect these two, or do the two connectors actually fit each other in the real life installation?

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    Thanks for the reply. In reality the attenuator gets bolted onto the end of the HRU. No ducting in between.

    The HRU in that image does actually have in-built attenuators that schedule separately and appear in the correct place when the user ticks a box but sometimes I get asked for ancillaries such as frost coils or filter modules that are not built in and normally I would then go through the motions of creating a custom model for them with all ancillaries present.
    I was just wondering if they already have the AHU in the their project then ask for a frost coil or similar that would need to be close-coupled would sending them just the frost coil family cause a problem. Seemingly, it might.

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    You can only but test it out and see if it works.
    But my hunch is that it will not connect the two as the "connector" is a physical(virtual) piece of duct - even if it is only millimeters long, its still there (in the model)

    Hence why I say probably better to have a family with the attenuators incorporated and only one connector coming out of it - not sure how this will affect the calculations coming out of revit though, so again...test and then test some more.

    Effectively, the technician can place it a minimum distance required by revit to recognise a connection, maybe you could adjust your connector placement on the attenuator so that graphically the box is the right size but the connecter is shifted back the minimum distance so that if the elements are placed face to face you will get an actual connection out of revit.

    If you have revit its pretty simple to test it yourself without much knowledge.

    Click your attenuator and click on "create system" and then "add Equipment" add your AHU and finish the system.

    Now select the system by alt tabbing and ask revit to propose a layout in the contextual menu. Before doing that I often select the elements individually and use the isolated 3D view icon that appears so I can see whats going on with just those elements in question because if there is vertical displacement you wont see the proposed layout properly in a plan view. Revit will draw lines to begin with blue and green usually, and any orange lines are going to be ducts that will not connect for some reason or another - this you can see before you place the lines while you are still in the preview mode. You can adjust the proposed parameters and change duct sizing and just make sure your main duct or branches are the intended size but this is usually linked directly to the connector size so with just 2 elements in your system is unlikely to cause you issues. Unless you have a transition of size between the AHU and attenuator, and in which case it will DEFINATELY give you an error because revit will be wanting enough space to place a transition piece between duct sizes.

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    Thanks for your help. I'll have a play about to see what works.

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    I actually just tested this myself and I can confirm that revit doesn't like the two connectors face to face. It needs a small piece of duct.
    So as I suggested already two possible solutions;
    1. Create a family with the atenuator incorporated and remove the connection in the middle of it (atenuator to AHU)
    2. Modify your atenuator family so that the conector is slightly displaced Inside the atenuator so it has enough distance to place a small sliver of duct that in reality shouldn't exist.

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    Great, thanks very much for spending the time to help me.

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    I would definitely go with Karalon10's option #1, above. The Attenuator should be part of the AHU family. If I were making this family, I would have a yes/no Parameter called "Sound Attenuator" and then control the length of the supply "stub" duct with a formula: if(Sound Attenuator, 36", 2").

    This extrusion (with the duct connector on the end), can then project through your nested Sound Attenuator family, which will have its visibility controlled by the same Sound Attenuator yes/no parameter. You can put a dimension on your Attenuator and lock it to 0", which will keep the Attenuator constrained to the end of your unit.

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    Thanks, this is exactly what I already do for the most part, but there are several ancillaries that can be added, not just attenuators and having them all in the family would cause the file size to be huge (plus all sorts of problems with getting them in the right order in different configurations, so I was just wondering if just sending the appropriate ancils separately would cause problems. I used the attenuator just as an example. Currently I make a bespoke model each time a unit is requested with differing ancils.

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    Quote Originally Posted by mrgrotey View Post
    Thanks, this is exactly what I already do for the most part, but there are several ancillaries that can be added, not just attenuators and having them all in the family would cause the file size to be huge (plus all sorts of problems with getting them in the right order in different configurations, so I was just wondering if just sending the appropriate ancils separately would cause problems. I used the attenuator just as an example. Currently I make a bespoke model each time a unit is requested with differing ancils.
    Necro's suggestion is exactly how I would do it.

    But, I wouldn't worry about the file size too much. Granted, there's obviously a threshold there, but if it's a great Family that has lots of good options in things like sound attenuator, canvas connection, etc, then hats off. Maybe keep each Family broken out individually for other to do things "their way", and keep the "uber Family" in tact for those who would use it.

    Family lean-ness is a good thing, but I'd opt for a heavier Family any day if it's worth it.

    -TZ

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