Chapter 9

Creating Logical Systems

Creating and managing systems is the key to getting Autodesk® Revit® MEP to work for you. Systems represent the transfer of information between families. They range from supply air to refrigerants to laboratory gases to anything else a building needs to operate.

In this chapter, you will learn to do the following:

• Create and manage air systems
• Create and manage piping systems
• Manage display properties of systems

Managing Systems

Systems are the logical connection between elements in the model. They are the link between the air terminal, the variable air volume (VAV) box, and the air handler, and they represent an additional layer of information above the physical connections made with duct and pipe. Without systems, ducts and pipes act only as connections between two points. Systems are needed to generate the bigger picture and allow you to manage the elements on a building-wide level. You can create systems to represent supply, return, and exhaust air as well as plumbing, fire-protection, and hydronic piping. You can also create systems to represent other uses of duct and pipe outside the predefined types included in Revit MEP 2013.

Systems aid in the documentation of a model. Because elements across the entire model are linked together, tags and other properties can be managed quickly and accurately. The best example of this is using a pipe tag that includes not only the size but also the system abbreviation. Tagging any piece of pipe connected to the system, in any view, will immediately generate a complete and accurate annotation.

Why Are Systems Important?

Managing systems is the only way to separate, say, a cold water pipe from a hydronic pipe. If you can't separate the two, you will simply not be able to produce sheets showing certain systems and hiding others. Prior to Revit MEP 2012 you had to create systems manually, and it was a fairly time-consuming process, especially keeping all of your systems properly organized throughout the design. But since Revit MEP 2012 you are able to create duct runs in a supply/return or exhaust system without actually creating a system in the first place. The neat thing about this is that the system can be changed on the fly. Of course, if a duct system is created by using the Generate Layout tool, the ducts assume the system of the host mechanical objects. Even though the ducts are associated with a system, managing space air quantities will need to be done externally. Entering all the information needed to accurately represent the mechanical systems in a building may seem like a daunting task at first, but the benefits of having all the information in one place and directly in front of the user can lead to more-accurate designs. Instead of the user flipping between a building-load program and a duct-sizing chart (or wheel) and trying to keep track of which terminal box is serving which space, systems can handle all of that for the user. By feeding Revit MEP 2013 the load information, calculated internally or externally, and creating an air system for a space, the user can quickly determine the cubic feet per minute (CFM) required at each air terminal with a schedule or a custom space tag. The airflow will then be assigned to the terminal box, and the space that it is serving can appear in a schedule. One program can handle all of these tasks, which the user would have to do anyway.

Using connected systems also carries a performance boost for Revit MEP. Even if systems are not being specifically set up, Revit MEP is using systems behind the scenes to keep track of all the information in the model. Revit MEP 2012 was the first version where you were allowed to enable or disable calculations per system type (Supply, Return, Exhaust, and so on), thus increasing the performance of the Revit model. This can be done from the Properties menu of the systems. All elements get placed on default systems based on the type of connector: supply air, return air, hydronic supply, and so on. This can be seen in Figure 9.1, which shows that objects are registered as Unassigned until they are connected.

Figure 9.1 Unassigned system objects

In the System Browser, if you expand the system tree, you can see that when an object is selected, the corresponding item is highlighted in the drawing area. In Figure 9.2, the objects are selected in the drawing area and highlighted in the System Browser.

Figure 9.2 Selecting in the drawing area

Conversely, selecting items in the System Browser highlights the objects in the drawing area, as long as the items are actually visible in that view (see Figure 9.3).

Figure 9.3 Selecting in the System Browser

Mechanical Settings

Before you can jump in and start creating systems, you need to set up several things to ensure that the systems work as they should. There is nothing wrong with the default settings, but every firm is different—each has its own standards, procedures, and often different design requirements. Most companies have developed standards over the years, and these are good guidelines to follow when using a new application such as Revit MEP 2013.

The Mechanical Settings dialog box, accessed from the Manage tab's Settings panel, contains some of the most critical settings for using systems in Revit MEP 2013 (see Figure 9.4). This dialog box was briefly covered in Chapter 2, “Creating an Effective Project Template,” but a more in-depth look is needed so that you can understand how these settings affect systems in Revit MEP 2013. All of these settings should be established in your company's project template. Changes to them should be discussed with the Revit team as well as the CAD manager, because visibility and graphics can be dramatically affected by a minor change in this dialog box.

Figure 9.4 Mechanical Settings dialog box

Several settings really affect systems graphically. For example, by choosing Duct Settings ⇒ Hidden Line, you see Inside Gap, Outside Gap, and Single Line. By default, each one of these is set to 1/16″ (0.5 mm). By changing the numeric size of each one of these parameters, you can get a different look that will help match your existing standards.

System Browser

The System Browser, shown in Figure 9.5, summarizes all the systems currently in the model. If that were all that it did, it would be a useful design tool. You could keep track of all the air and water in the building and see your system totals at a glance. But the System Browser in Revit MEP 2013 takes this idea a step further; it is a live link to the components in the system as well as their parameters. You have full control to modify the airflows, equipment types, and diffuser selection, all from a single window.

Figure 9.5 System Browser

You can access the System Browser from the Analyze tab or the keyboard shortcut F9. The first thing you should set up are the columns it displays. The System Browser can get very large, so a second monitor is helpful. You can access the Column Settings dialog box by clicking the Column Settings button in the upper-right corner of the dialog box, which gives you an expandable list of the information that can be referenced in the model (see Figure 9.6).

Figure 9.6 Column Settings dialog box

Obviously, not every parameter will be filled out for every part of the system, and some of the parameters will not be useful on a day-to-day basis. The columns you choose to display will rely on your personal preferences and how you model your systems. For example, Space Number and Space Name will populate only if the element and space touch. If spaces are bound by the ceiling, and terminal boxes exist above the ceiling, they will not be associated with a space. You will need to use the Show command to find lost terminal boxes. To do this, right-click any element in the System Browser and select Show.

Ideally, every connection on every piece of equipment would be associated with a system, and the Unassigned system category would be empty. This may not be realistic on a large job or where manufacturer content is being used. You may not model every condensate drain, but if the manufacturer has provided a connection point for it, there will be a listing in the System Browser. If your firm decides to use the System Browser to carefully monitor the systems and elements in the model, you may want to eliminate connectors that you will not be using to keep things clean. To do this, you will have to create a duplicate family and remove the connectors you do not want to use.

Setting Up Air Systems

Duct connectors in Revit MEP allow the user to connect ductwork to a family that may represent an air terminal, fan, VAV box, air handler, or chilled beam. Duct connections can also be used as a source for boiler combustion air and flues. There are many different applications of duct connections beyond a simple supply air diffuser. In this section, you will learn how to set up many different kinds of systems using duct connections.

Understanding Parameters

It takes a good understanding of the parameters besides height and width (or radius) before you can set up complex air systems. There are 14 parameters associated with a duct connector when its System Type is not set to Fitting. Not all of the 14 are active all the time (see Figure 9.7).

Figure 9.7 Parameters for duct connection

If the connector System Type is set to Fitting, the connector has only six parameters. Revit MEP has several System Classification types available for duct connections that facilitate system creation and view filters within a project (see Figure 9.8).

Figure 9.8 System Classifications for duct connections

Starting at the top, here is an explanation of each duct connector parameter shown in Figure 9.7:

Global Systems

Global systems are perhaps the most flexible option under the System Classification parameter.

However, they can also be the most dangerous for users not familiar with the way Revit Air Flow data works or those who are simply are overlooking it. When System Classification is set to Global, the users will be given the opportunity to choose the System Type. Just keep in mind that you will not be able to change the Flow Direction setting and therefore it should be only used for systems with similar Flow Direction, like Return, Exhaust, and Relief. Supply Air uses the opposite Flow Direction and therefore would require a separate family. If you don't pay attention to this little fact, your systems will lose their Air Flow data.

Creating Mechanical Systems

Now that you have reviewed the parameters of the mechanical systems that exist, you will now learn how to apply them in a simple exercise:

1. Open the Chapter9_Dataset.rvt file found at www.sybex.com/go/masteringrevitmep2013.

2. Download the Supply Diffuser - Perforated - Round Neck - Ceiling Mounted.rfa family. Next, choose Insert ⇒ Load Family, browse to where you have downloaded the family, and click Open (see Figure 9.9).

Figure 9.9 Selecting a supply diffuser

3. Now download VAV_SingleDuct_4-16inch_break object styles.rfa located at www.sybex.com/go/masteringrevitmep2013, and insert it into your model (see Figure 9.10).

Figure 9.10 Loading a VAV single-duct family

4. After downloading all of your components, you will want to place the diffuser onto the ceiling shown in the 1 - Ceiling Mech view. Because this family is a face-based family, it will automatically attach to the ceiling surface. Make sure to select Place On Face located under Modify | Place Air Terminal. If you don't, the diffuser will try to attach to the wall (see Figure 9.11).

Figure 9.11 Placing ceiling diffuser into ceiling grid

5. Once you have placed some diffusers, use the Mechanical Equipment tool on the Home tab to place the downloaded VAV box above the ceiling at an elevation of 10′–0″ (3048 mm). You can adjust the elevation by changing the elevation Offset in the properties (see Figure 9.12). It is important to set the elevation prior to placement if you are in a reflected ceiling plan view, or you may not see the VAV box when it is placed.

Figure 9.12 Changing elevation offset for the correct elevation of equipment

6. Now that the VAV box and diffusers are in place, you will want to make them part of a system. Select a diffuser and click the Duct button on the Create Systems panel of the Modify | Air Terminals contextual tab (see Figure 9.13). This activates a dialog box, shown in Figure 9.14, that allows you to choose the System Type and to assign a name to the system.

Figure 9.13 Creating a supply duct system

Figure 9.14 Create Duct System dialog

7. Once you have made the system by clicking OK, the Modify | Duct Systems contextual tab is active on the Ribbon. Click the Edit System button. Select Add To System, and select the other air terminals (see Figure 9.15).

Figure 9.15 Editing supply duct systems

8. Now click the Select Equipment button, and select the VAV box to be the equipment for your system. Click the Finish Editing System button to complete the system.

9. With the system created, select any of the diffusers in the System Browser, as indicated in Figure 9.16. Notice that this selection also selects the appropriate diffuser in the drawing area. This feature was first introduced in Revit MEP 2012, and it gives you greater control and manageability of objects.

Figure 9.16 Selecting in System Browser

Now that you have created your system, you can route your ductwork and it will take on the characteristics of the system parameters you set up. Understanding how to make mechanical systems will offer you the benefit of being able to create any duct system you may need for your design. For further instruction on how to route ductwork, refer to Chapter 10, “Mechanical Systems and Ductwork.”

Another new feature that was introduced for the first time in Revit MEP 2012 was the ability to automatically create systems on the go as you route your ductwork/pipework. You no longer need to create systems manually as in the previous exercise. Simply connect the supply duct to any diffuser and watch it become part of that system. But disconnecting the duct that “pushed” the system to the diffuser will not remove the diffuser from the system. Therefore, understanding how to create and manage systems manually will still be necessary.

Setting Up Piping Systems

Mechanical piping benefits greatly from systems in Revit MEP 2013. Graphics, annotations, flow, and pressure loss can all be handled with a small amount of setup in your project template. Pipe systems also allow filters to apply to all components in the system, including the fittings. As discussed earlier in this chapter, Revit MEP 2012 introduced new enhancements in how systems behave, which are still valid for Revit MEP 2013. Also, the enhanced System Browser acts as a graphical pointer to the designer with regard to how objects are connected in systems; it also has a huge benefit on how the actual systems perform.

The first of these benefits is the ability to predefine the system in which pipes (and ducts) are created, allowing layouts to be designed without the need to set up systems in the first place. This allows the designer to create Hot Water (HW) and Cold Water (CW) pipe runs with graphical filters already in place to display the different systems being created.

Second, this allows for different systems to be interconnected. In previous versions of Revit MEP, it was necessary to employ a variety of workarounds in order to have, for example, a sanitary pipe system connected to a vent pipe system. Since Revit MEP 2012, all designers have to do is specify the system type they want to create. Figure 9.17 displays Sanitary and Vent pipe systems with the system Sanitary 2 selected. When working with multiple systems that are connected, it is important to note that a fitting, accessory, or equipment is needed between the two pipes/ducts in order for the separation of the systems to work. When the system change occurs at an elbow or tee, all is good, but when you want to change the system continuing the pipe/duct in the same direction as the original one, you need to use the Split tool, which will insert a coupling fitting, and therefore you can have two different systems.

Figure 9.17 Dual pipe systems

As the design progresses, systems may need to be merged with these new “systemless” systems. All the user has to do is connect the two systems together. Figure 9.18 shows that after the two sanitary systems are joined, they effectively become one system with no further interaction required.

Figure 9.18 Merged systems

Understanding Parameters

Parameters for piping are similar to the parameters for air systems such as Flow Factor, Calculated, Preset, Flow Direction, and so on. The available pipe system types are as follows:

Creating Pipe Systems

You will need to define pipe types, load some fitting families, and have something to which they will all connect to create pipe system. Equipment is the source of the system, and the pipe and fittings connect everything. It seems pretty simple, but there are several things to consider when setting up the components of a pipe system.

The Pipe Type Properties in Revit MEP 2013 have been completely reorganized (see Figure 9.19). Now you have the ability to assign Routing Preferences by size. For example, you may want to use a certain type of fitting only when routing pipes under 6″(152 mm) and another type of fittings for pipes over 6″ (152 mm) (see Figure 9.20). In addition, the old usage of Materials has now been moved under Routing Preferences and renamed to Pipe Segment. The pipe types should all reflect real-world values and the company standards and specifications. Even if you are not using Revit to size or lay out pipe automatically, not setting up the appropriate pipe types can cause headaches down the road. Pipe types should not be left at Standard and PVC. Those hardly cover the necessary piping that a building requires and, more importantly, the plumbing and mechanical engineering will be fighting over what fittings should be standard and what materials should be used. Mechanical piping and plumbing piping should have their own pipe types. Even if exactly the same materials and fittings are being used, there may be changes later, and splitting out pipe types late in a project will undoubtedly eat up a lot of time. This is one area of Revit MEP that enables you to have as many types as you want, so take advantage of it.

Figure 9.19 Pipe Type Properties

Figure 9.20 Routing Preferences

Pipe Segments And Sizes are set up in the Mechanical Settings dialog box (see Figure 9.21), and similar to pipe types, they should be separated for plumbing and mechanical piping. In many instances, you would probably be fine using the same material and sizes, but when differentiating them is as simple as selecting the Add Material icon and selecting a source from which to copy, there is no reason not to create as many sizes and materials as needed. All of these settings should also be determined by using the company standards and specifications. It may seem tedious to set up, but if the inside diameter of a 6″ (152 mm) hot water pipe is not true, and you are using a lot of it, your pipe volume calculations can be skewed.

Figure 9.21 Pipe sizes

Fittings should be set up after sizes and materials for a couple of reasons. First, the connection type needs to match. A solvent-welded PVC fitting and a flanged steel fitting are vastly different. Second, the fittings need to be defined at all the available sizes for that type of pipe; if it goes down to 3/8″ (10 mm) or up to 36″ (914 mm), the fitting needs to accommodate. Fittings are specific to the type of system, which is another reason to separate pipe types for plumbing and mechanical uses.

Hydronic systems have value even if the equipment is not piped together. Terminal box reheat coils are a good example, because details generally cover their final connections. By simply adding all the terminal boxes to a hydronic supply and hydronic return system, you will be able to see the total flows for the entire model. You can use this flow summation to ensure that systems are adding up to what you expect and to compare flows between systems.

Creating Fire-Protection Systems

Fire-protection systems in Revit MEP are a sort of hybrid between air systems and hydronic systems. Sprinklers, from a system standpoint, are similar to air terminals. Sprinklers are designed to distribute a fluid evenly over a given area, with pressure as the driving force of distribution. In the case of fire protection, water is the fluid, and the fire pump or city connection provides the pressure.

The key to a good, manageable fire-protection system is the families. Decide what type of system you will be using, and make sure appropriate families are developed before you or other users start laying out components. Revit MEP does have the ability to load a family in the place of another, but that tends to cause issues with system connections, pipe connections, and hosting. Sprinklers, standpipes, hose cabinets, and fire pumps may have to be created for the systems to work properly.

Setting Display Properties of Systems

Revit MEP 2012 was the first version to introduce system families for duct and pipe systems. These can be found in the Project Browser under Piping System and Duct System.

System families can have additional types created in the same way as other loadable families, by right-clicking any one of the existing types in the Project Browser and duplicating it. It is important that you choose carefully—a duplicated Domestic Hot Water piping system cannot be changed later to a Domestic Cold Water piping system.

With these new system families come new parameters: System Abbreviation and System Classification. Beginning with Revit MEP 2012, you have the ability to tag any pipe (or duct) and refer to the system type of what may be a system with no equipment assigned. You could not achieve this in previous releases without manual workarounds.

System Filters

To set up system filters, you need to select the View tab on the ribbon and then choose Visibility/Graphics ⇒ Filters (see Figure 9.22). You will then notice that, in the Filters dialog box, there are several filter names that are in Revit MEP by default.

Figure 9.22 System filters

You will also notice that there are categories that have different elements selected. These are the items you want to have affected by the filter. Next, you will notice under Filter Rules that, by default, System Classification is selected. Because of the large number of filters that are normally created for a project, you should change the Filter By setting from System Classification to System Abbreviation. This will help to identify and separate your systems properly. To create new system filters, the easiest method is to select an existing system filter and then click the Duplicate icon. Once the system filter is duplicated, make sure the proper category elements are selected and then rename the filter rule to the name by which you want to filter.

To apply these filters to your views, you can go to the View tab on the ribbon and then select Visibility/Graphics. Next, select the Filters tab (see Figure 9.23).

Figure 9.23 View filters

Once you have selected the Filters tab, click Add. This brings up the filters that you have created, so select the filters that apply to your project. Once the filters are loaded, you can turn on and off the filters and adjust line weights, colors, and patterns.

Mastering filter options will give you the ability to create your models with the standards that your office has developed over years of producing CAD drawings.

Filters Save the Day

James has been working on a medical facility in Revit MEP 2013. When he completes the project, he submits it to the state review board to make sure that the plans meet the state requirements for standards of care for health facilities. The only comments from the reviewer are that she would like to have the different duct systems shown with different patterns to help tell the systems apart more clearly. To accomplish this, James uses system filters to distinguish the different duct systems. The following steps show how he accomplishes his goal:

1. After using the shortcut VG to open the Visibility/Graphic Overrides dialog box, he selects Filters ⇒ New/Edit. Next, he duplicates Mechanical - Supply (twice) and renames the new filters Mechanical Supply Air 1 and Mechanical Supply Air 2, as shown here.

2. Next, he changes the Filter Rules from System Classification to System Name and changes the Contains statement to Mechanical Supply Air 1. He repeats the process for Mechanical Supply Air 2.

3. Once he has his filter rules created, he adds them to his filters and then adds patterns to help show the difference between the two supply systems.

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