Revit Mechanical Systems

Posted on Apr 8, 2013 | No Comments
  • Revit Mechanical

So we have been working with the 4th year architectural students and the University of Arkansas and they have been having some issues with modeling mechanical systems in their proposals. Well, we have some experience with this and since the studio, as a whole, seems to be having issues grasping this process we thought that we’d go over some modeling concepts that make the whole process easier. We will follow up with this post with a video tutorial shortly but we felt that we needed to get some information out there as soon as possible.

Mechanical systems in Revit are modeled the same way as structural systems. You have to define the pieces in the system before you start to model the specifics of the system, such as air terminals and fittings. By default, if you started your model with an architectural template, the mechanical systems have no connections defined in their type. So any time you try to model a duct system you are greeted with the following error; “The routing solution failed because there is no default fitting type specified or the fitting cannot be found in the project. Ensure the fitting is loaded in the project and try again.” To correct this error all you have to do is define the connections that are possible for that specific system. To do this, select the duct system that you wish to model then click on edit type, then click on the “Edit” button next to routing preferences and you will then be greeted by the “Routing Preferences” menu. Click on the image below if you are still having trouble finding this menu. It explains how to get there step by step.

  • Duct Settings

In this menu, you can quickly load all the specific duct fittings for any connection or transition that your mechanical system could possibly make. Once you have loaded your families and have applied them to the particular connections, you can now return to your project and model, very quickly, your desired mechanical connections.

Some other concepts to keep in mind when starting out modeling duct-work:

1. Don’t create a level just for hosting your mechanical systems. This will destroy any view range settings that you already have in your project. The mechanical system is very robust and can handle level offsets quite well, so use them.

2. Always specify supply or return in the type menu before you model any duct work. You don’t want to find out that you modeled all your duct-work backwards. (I have done this, so, you can too.)

3. Don’t get too caught up in making rigid connections from your ducts to your air terminals. Flex ducts are used all over the place in the real world. If you have an air terminal that just cant be aligned with a particular duct, just use a flex duct. It will save you much time and headache.

4. Verify that your system is connected. Nudge your system around with you arrow keys when you have finished modeling the duct-work. If all the connections move together than you have modeled a “closed” system. Congratulations!

If you have any other questions in regards to mechanical systems drop us a line at or leave a comment in the section below.

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