Admittedly, it is possible to complete a project through construction documents in Revit MEP 2011 without using systems. Some workarounds are required to accurately create tags, and 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 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 2011 the load information, calculated internally or externally, and creating an air system for a space, the CFM (Cubic Feet per Minute) required at each air terminal can be quickly determined 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 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. All elements get placed on default systems based on the type of connector: supply air, return air, hydronic supply, and so on. When the default system exceeds 50 elements, a warning message appears (Figure 8.1).

Figure 8.1. Fifty elements warning message

Using systems can eliminate this issue and a few others. For example, if an air terminal is not placed on a system, it cannot be rehosted to a new face. This can be a major problem at the 11th hour when an air terminal that has lost its host needs to be coordinated with the latest reflected ceiling plan.

Before you can jump in and start creating systems, you need to set up several things to ensure systems work as they should. There is nothing wrong with the default settings, but every firm is different, and so are their standards and procedures. Most companies have developed standards over the years, and these are good guidelines to adhere to when using a new application such Revit 2011.

The Mechanical Settings dialog box, accessed from the MEP Settings panel's Manage tab contains some of the most critical settings for using systems in Revit MEP 2011 (Figure 8.2). This dialog box was briefly covered in Chapter 2, but a more in-depth look is needed so you can understand how these settings affect systems in Revit MEP 2011. All of these settings should be established in your company's project template, and 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.

Several settings really affect systems graphically. For example, under Duct Settings ⇨ Hidden Line, here you see Inside Gap, Outside Gap, and Single Line. By default, each one of these is set to 1/16". By changing the numeric size of each one of these parameters, you can get a different look, which will help match your existing standards.

The System Browser, shown in Figure 8.3, summarizes all the systems currently in the model. If that was 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 2011 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 8.2. Mechanical Settings dialog box

Figure 8.3. System Browser

You can access the System Browser from the Analyze tab or the keyboard shortcut F9. The first thing you will want to set up is the columns it displays. It can get very large, so a second monitor is very helpful. You can access the Column Settings dialog box by right-clicking in the System Browser, which gives you an expandable list of the information that can be referenced in the model (Figure 8.4).

Figure 8.4. 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.

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 connection when it is not set to Fitting. Not all of the 14 are active all the time (Figure 8.5).

Figure 8.5. Parameters for duct connection

If the connector is set to Fitting, it has only six parameters. Revit MEP has several system types available for duct connections that facilitate system creation and view filters within a project (Figure 8.6).

Figure 8.6. System types for duct connections

Starting at the top, here is the explanation of each duct connection parameter:

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

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.

Figure 8.12. Editing supply duct systems

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:

You will need some pipe, some fittings, and something to which it will connect. 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.

Pipe types allow you to assign materials, connection types, identity data, and the fittings that will be used to connect it all together (Figure 8.13). Material, Connection Type, and Class are all set up in the Mechanical Settings dialog box. These 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. That hardly covers the necessary piping that a building requires, and more importantly plumbing and mechanical 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 where you can have as many types as you want, so take advantage of it.

Pipe sizes and materials are set up in the Mechanical Settings dialog box (see Figure 8.14) and, similar to pipe types, should be separated for plumbing and mechanical piping. There are many instances where you would probably be fine using the same material and sizes, but when it 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 as are needed. All of these settings should also be determined using the company standards and specifications. It may seem tedious to set up, but if the inside diameter of a 6" hot water pipe is not true and you are using a lot of it, your pipe volume calculations can be skewed.

Figure 8.13. Pipe type properties

Figure 8.14. Pipe sizes

Fittings should be set up after sizes and materials for a couple 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" or up to 36", the fitting needs to accommodate. Fittings are going to be very specific to the type of system, which is another reason to have pipe types for plumbing and mechanical separate.

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.

Quickly Adding Equipment to a Piping System

If the equipment you want to add to a hydronic system is all the same family and type, you can simply right-click one of the elements, select All Instances, and click the Hydronic Return/Supply/ Other System button.

Now if your equipment has multiple types, this trick doesn't work as well. Start with the most common type, and use the Select All Instances trick. Once the initial system is created, edit it to add the remaining components. Unfortunately, the Select All Instances feature is not available within the Edit Systems menu. You can, however, drag a selection box to grab multiple pieces of equipment.

New to 2011 Revit MEP, the Select All Instances feature now has two options — Visible In View and In Entire Project. These new options offer more flexibility than the previous versions.

Fire protection systems in Revit MEP are a sort of hybrid between air systems and hydronic systems. Sprinklers, from a system standpoint, are very similar to air terminals. They are designed to evenly distribute a fluid 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.

To set up system filters, you need to select the View tab on the ribbon and then select Visibility/Graphics

Figure 8.15. 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 Type is selected. Because of the large number of filters that are normally created for a project, you will want to change the Filter By setting from System Type to System Name. This will help to properly identify and separate your systems. 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 you want to filter by.

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 (Figure 8.16).

Figure 8.16. View filters

Once you have selected the Filters tab, select Add. This will bring up the filters that you had 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 the years producing CAD drawings.

Real World Scenario: Filters Save the Day

Jamie Abbott had been working on a medical facility in Revit 2011. When he completed the project, he submitted it to the state of Tennessee review board to make sure that the plans met the state requirements for standard of care for health facilities. He has just received the review comments, and the only comment on the review is that the reviewer would like to have the different duct systems shown with different patterns to help clearly tell the systems apart. To accomplish this, Jamie used system filters to distinguish the different duct systems. The following steps show how he accomplished his goal

1. He pressed VG to bring up Visibility Graphics; then he selected Filters

   
   

2. Next, he changed the filter rules from System Type to System Name and then changed the Contains statement to Mechanical Supply Air 1. He repeated the process for Mechanical Supply Air 2.

   

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