When using the automatic routing tools, as a rule of thumb you should work on small sections—all the feeds to a VAV box is one good example. This means the computer has fewer objects to and the routing suggestions have less room for error. Before even starting this process, check the options under Mechanical Settings (see Figure 10.14) for default duct types, offsets,
and length of flex duct because these are used during the routing process. Also note that these settings can be set for the different system types.
Now you’re ready to use automatic duct routing. Here’s how:
1. Place your VAV box, ensuring it is located at the correct height. You can change it later if needed, but this may lead to you changing your duct route.
2. Place your air terminals. At this point, it is a good idea to consider the following, not from a design point of view but from a Revit one:
What type are the ceilings (if any)? •u If there are ceilings, should you use face, ceiling, or nonhosted families? •u
Are you going to create your own placeholder ceiling to host your families? •u
Should you use the new ability to copy/monitor the air terminals already placed by •u the architect?
Choose the type of air terminal. Is it top, side, or even sidewall entry? •u
3. Once you’ve made all these decisions, it’s time to start laying out the equipment. Figure 10.15 shows (1) a space where the upper limit of the space has been defined as the level above; (2) the specified supply airflow has been entered manually; (3) calculated supply airflow is not computed because the analysis tools have not been used for this building; and (4) the flow
rates for the air terminals have been adjusted to suit the calculation.
4. Creating a system has become easier in Revit MEP 2012 than in previous releases. You can either select one air terminal, create the system, and then add others, or you can select all the air terminals you want to be in the system. On the ribbon, select the Duct option on the Create Systems panel (Figure 10.16).After you click the Duct button, the Create Duct System dialog box displays, as shown in Figure 10.17.
This allows you to edit the system name and, if necessary, open the new system in the system editor to add/remove additional objects and select equipment. Objects that are not Figure 10.15
Space properties part of the current system appear as halftone in the drawing area. When they are selected to be added to the system, their appearance changes to full weight (see Figure 10.18).
5. Once you have completed adding air terminals, click Select Equipment, and either select the equipment from the Options Bar drop-down or select the actual VAV box indicated on the plan, as in Figure 10.18.
6. Complete this task by clicking Finish Editing System. This is where the fun begins!
7. Hover over one of the items in the system (but do not select it) and press the Tab key.
All the items in the system—air terminals and the VAV box—will now be enclosed in a dotted box. Without moving your cursor, left-click. This selects the system, as shown in Figure 10.19, and displays the system in the System Browser.
System dialog box
Add To System
8. With the system selected, you now have several options; one of these is to create a duct layout. New to Revit MEP 2012 is the option to use placeholder ducts. Select Generate Placeholder and, as shown in Figure 10.20, the sketch options for layout are displayed.
Select Network, option 4. Remember that you can also edit the default settings for the duct offsets, as shown earlier in Figure 10.14, by clicking the Settings button on the Options Bar.
9. There are several options for automatically generating your duct layout. These include Network, Perimeter, and Intersection options. Each of these can give you several solutions that can vary depending on the predefined settings for the duct layout, which can also be accessed from the Options Bar. Figure 10.21 shows that you can click the Edit Layout button, which allows you to select the layout lines in order to make changes to the layout.
10. Main duct runs are shown in blue, while branch runs are shown in green. Once you have settled on your preferred layout, click Finish Layout, and the duct layout is created (see Figure 10.22). Notice that the placeholder ducts are shown only as a single line
It’s worth pointing out here that the sizes used for this layout are based on the connection sizes and the settings for duct sizes located in the Mechanical Settings dialog box. There is another important consideration at this point.
The designer/drafter must ensure that the default settings for the main and branch ducts are adequately high enough above the air terminals and
associated equipment to generate the layout; otherwise, the layout tool will not be able to generate a layout, even if the layout is created with placeholder ducts.