Chapter 19
Creating Equipment
The equipment families used for the design of your MEP engineering systems are important—not only for coordinating the physical model, but also for establishing the components that serve as the equipment for your engineering systems. The properties you assign to your equipment families will define how they can be used in relation to other components within a system.
Many mechanical and electrical equipment items require clearance space for maintenance and installation. With the Autodesk® Revit® MEP 2014 software, you can define the required clearances for equipment families either directly in the family files or as a separate component. This gives you the ability to coordinate your model fully to avoid costly conflicts during construction.
Creating equipment families that are generic enough for use early in the design process, yet parametrically changeable, will help you transition through design phases and changes to systems smoothly and efficiently. The physical properties of MEP equipment are similar enough in most cases to use simple geometry that can be sized according to specified equipment.
Whether you are creating equipment for mechanical, plumbing, or electrical systems, knowing how the equipment will be used from an engineering standpoint as well as a modeling standpoint will help you create the types of families that fit your workflow and processes best.
In this chapter, you will learn to do the following:
- Create MEP equipment families
- Add connectors to equipment for systems
- Create clearance spaces for equipment
- Add parameters to equipment
Modeling MEP Equipment
With the rising popularity of building information modeling (BIM), more and more manufacturers are providing their products for use in a virtual model environment. This can be very useful when you get to the stage in your design where you can specify the exact equipment to be used. Early in the design, however, you may not know what equipment will be used. Furthermore, you may not yet have done calculations that would determine the size of the equipment needed.
All of this boils down to a need for MEP equipment families that are realistic in size and function, but also parametrically editable to compensate for changes in the design of both the project and the systems used. These families need to be flexible enough to handle the seemingly constant change that occurs early in the design process, but they also need to have the functionality to represent their intended purpose accurately.
Some of the resistance to adopting a BIM approach for designing a project stems from the fact that too much information is required early on that is not known in a typical project environment. Having usable equipment families can alleviate some of that concern and allow you to move forward with your design processes.
Hosting Options
When planning for a family, there are plenty of things to consider. One of the first is how the family will be placed into a project model. Is the equipment inline with duct or pipe? Does the equipment require a building element to which it will be attached? Knowing the answers to these types of questions will help you start with the right family template so that the equipment you create can be used properly in your projects.
Generally speaking, there are three hosting family behaviors: generic, face-based, and object-based. The generic families are the most common families, and they are not constrained to any adjacent geometry; instead, they are constrained to the level they are placed on. Face-based families are commonly used as grills, diffusers, plumbing fixtures, and so on. In order to place those families, you need to have a present host (wall, floor, counter, and so on). The host can be either in your MEP model or in any Revit linked files. Object-based families are almost never used in Revit MEP. This is because they require the physical presence of the host in your model, and they can't be placed on hosts that exist in any of the linked Revit models. In other words, you can’t place any object-based diffusers on the architectural ceiling, unless you have ceiling objects modeled in your own MEP model (not through the link).
To make the right decision about what hosting behavior you should choose, you need to know the pros and cons of those behaviors.
Generic (nonhosted) families behave pretty much like any other object in Revit—they change location only if you move them.
Object-based families behave like face-based families for the most part, except that they need the host to exist in the model and not be part of a linked Revit file.
Face-hosted families have one major advantage: They follow the plane of the host. Anytime the architect adjusts the ceiling location, your diffusers will adjust accordingly. Cool, right? Ceiling diffusers follow the elevation of the ceiling, and the water closet follows the plane of the wall (not the elevation, but the actual plane of the wall finish). Ironically, this advantage is its biggest disadvantage. It is important to understand that as your objects move with the hosted element, any connected pipes or ducts can potentially disconnect and break the integrity of the system. Interestingly enough, the behavior in Revit MEP 2014 is different from all previous versions. Revit MEP 2014 will move the hosted elements with the host, disconnecting your systems without any notification. In all previous versions, when you receive the new architectural background and try to open your MEP model, you will get the message shown in Figure 19-1.
Figure 19-1 Message when using face-hosted families
This message, as you can see, has only two options: Delete Element(s) will delete some pipes, pipe fittings, ducts, and duct fittings; Cancel will cancel the process of opening your project. The bottom line is that in order to open your project, you must delete certain elements. You may ask yourself which elements Revit is trying to delete and why. When you are designing with Revit MEP, all pipes and ducts should be connected, and as you move a main piece of pipe, any branches should extend or shorten, right? Knowing that fundamental behavior of Revit, let’s translate it to a face-hosted family that is following the host. Let’s say you have placed a plumbing fixture on top of the architectural plumbing fixture; the only difference is that your plumbing fixture has a connection point where you can connect your pipes, as shown in Figure 19-2.
Figure 19-2 Connected plumbing fixture
When the architect relocates the hosting wall (toward or away from the main), your plumbing fixture will follow. And of course, Revit will do its best to maintain the integrity of any connected pipes. Therefore, the short pipe coming off the main will either extend or shorten. Now, let’s imagine that the architect moves the wall past your main. What do you think Revit will do? You guessed it: Revit will not know how to reconfigure the whole system, and will simply try to delete the short pipe. This is why you’ll get the message that certain elements need to be deleted.
Once you accept the message and open your model, the only way to find which pieces have been deleted is to inspect the entire model visually. This can be a time-consuming and frustrating process.
Face-based families are powerful and at the same time dangerous. As a rule of thumb, you should consider creating face-based families for any objects that require following the host but don’t have any connected elements (receptacles, thermostats, switches, and so on). When you have elements connected to the object, proceed with caution because those connections may break.
Equipment that sits on the floor of a room or at the exterior of a building does not need to be created as a hosted family. When you place a nonhosted (generic) family into your project, it will be associated with the level of the view in which it is placed. However, if the equipment requires a pad for housekeeping or structural support, you may want to make the family face-hosted so it can be attached to the face of the pad. This will allow for coordination with changes to the pad, assuming that the structural engineer or architect provides the pad. If the equipment you are creating always requires a pad, you can build it directly in the equipment family—that’s assuming that you are responsible for placing and sizing the pad. When the structural engineer is responsible for the equipment pad, you can use the offset parameter of your mechanical equipment to elevate it on top of the pad.
Once you have determined the hosting behavior of an equipment family, you can build the solid geometry of the equipment in relation to the host object or reference plane that represents how the family will be placed into a model.
Family Categories
There are essentially two choices for categorizing your equipment families: Mechanical or Electrical Equipment. This may seem limiting, but keep in mind that you can make any subcategories you choose. It may be necessary to categorize an equipment family as some other model category, depending on how it is used in your projects. This is typically done for visibility control or scheduling purposes, although for scheduling the most common way is to use a parameter for filtering out just the equipment you want to display in your schedule. Variable air volume (VAV) boxes need to be in a separate schedule than boilers, although both of are mechanical equipment. By creating a parameter such as Schedule Filter and assigning the value in the VAV box family to, say, VAV, you will be able to schedule (filter out) VAV boxes separately from the other equipment in the project.
To continue from where we left off when we started creating a family, select the file Generic Model.rft and click Open. You can set the category of a family by clicking the Family Category And Parameters button on the Create tab in the Family Editor, as shown in Figure 19-3.
Figure 19-3 Family Category And Parameters button
When you categorize a family as Mechanical Equipment, you can set its behavior with the Part Type parameter, as shown in Figure 19-4. The Normal option is for equipment that is simply placed into the model and stands on its own, while the Breaks Into option is for equipment that is inline with ductwork or pipe. The Breaks Into option allows you to insert the family directly into a run of duct or pipe without having to first create an opening for the equipment.
The Part Type parameter for Electrical Equipment families also has options for defining the equipment behavior, as shown in Figure 19-5. These options let you define how the equipment is used in an electrical system.
If you choose the Panelboard option, you can set the configuration of the breakers and circuit numbering in the panel. This corresponds to the template used for panel schedules, as shown in Figure 19-6. Panel Configuration, along with Part Type parameters, defines the relationships between panels in the project schedules. Therefore, careful consideration is advised.
Another family parameter that you should consider is the Always Vertical option. Selecting this option causes the equipment family always to appear vertical at 90 degrees, no matter how the host is sloped. This setting is used for nonhosted families. If you are creating a nonhosted family and you want to be able to place the family in any orientation, you can set the Work Plane-Based option. This allows you to place a nonhosted family onto any workplane defined in your project. Otherwise, if you place a nonhosted family into a project and it is associated with the level of the view placed, you will not be able to rotate the family in section or elevation views.
Figure 19-4 Part Type options for Mechanical Equipment
Figure 19-5 Part Type options for Electrical Equipment
Figure 19-6 Panel configuration for electrical equipment
Setting the family to Work Plane-Based does not mean that you can rotate the family in section or elevation, but you can create a reference plane that is at the desired rotation in the project and associate the family with that plane, as shown in the section view in Figure 19-7. When you place a Work Plane-Based family into a project, the option to place the family onto a face is available on the Placement panel of the contextual tab.
Figure 19-7 Work Plane-Based equipment in a project
This functionality is useful because it allows you to use nonhosted families in a face-hosted fashion.
Detail Level
When you are modeling your equipment families, consider the amount of detail required to represent the equipment. Mechanical components can be complicated structures that include many intricate parts. It is not necessary to model your equipment families to a high level of detail for them to function properly in your projects. If you need to show equipment with a lot of detail, you can use model lines or symbolic lines to represent the equipment in views where the high level of detail is needed while keeping the family geometry simple.
Most equipment families can be modeled using simple geometric forms such as cubes and cylinders. If the equipment family you are creating requires more-complex geometry, you will need to use the other modeling tools available in the Family Editor, such as the Sweep, Blend, and Revolve tools.
For instances where you need to show only the amount of space required for equipment, you can model it as a box that is visible in Coarse detail views. More-detailed geometry can be modeled to show in views with a finer level of detail. The important thing to remember when using this technique is that the connection points for ductwork or pipe should be located on the outer edges of the box geometry. Otherwise, you might end up with pipes and ducts that appear disconnected, as shown in Figure 19-8.
Figure 19-8 Pipes and ducts that appear disconnected when in medium detail level
Geometry for Connection Points
MEP discipline equipment families can include connectors for ducts, pipes, conduit, and even cable trays if necessary. These connectors are added to define the function of the equipment from an engineering standpoint. Connectors are added by one of two methods: either by placing them on a face of the solid geometry, or by associating them with a workplane within the family. When you associate a connector with a workplane, it can be located anywhere in that plane. Connectors placed with the Face option on the Placement panel of the contextual tab will automatically attach to the center of the face.
Using the Face option is useful when you know that the connection point is always at the center of the geometry—because if the geometry changes size, the location of the connector will adjust, or if the geometry changes location within the family, the connector will move with it. This method requires less constraint within the family for the location of the connector, but it may be necessary to model extra geometry to provide a correctly located face for a connector.
Creating geometry for the location of connectors is an easy way to manage not only connector locations but also connector sizes. The size of a connector can be associated with the size of its geometry host face. This allows for accurate modeling of connection points of different family types within a family.
Geometry used for connection points may be more easily dimensioned than connectors themselves because you can dimension to the edges of geometry, whereas connectors can be dimensioned only to their center points. For example, if you have a rectangular duct connection that varies in size yet needs to maintain a certain distance from the edge of the unit, you can model geometry that is constrained to the dimensional requirements and then host the connector to that face. Figure 19-9 shows an example of an extrusion used in this manner. The 0′-6″ (150 mm) and 0′–4″ (100 mm) dimensions are locked to hold the extrusion in place when the UnitHeight and UnitWidth parameters are changed, and when the SupplyHeight and SupplyWidth parameters change.
Figure 19-9 Extrusion used for connector host
Using extrusions for connection points can make it easier to identify where to connect pipes, duct, or conduit to your equipment when working with the family in a project. More information on connector geometry is provided in the next section of this chapter.
Equipment Pads
When you are creating an equipment family that needs to be mounted on a pad, it may be best to include the pad geometry directly in the equipment family. This enables you to ensure that the appropriate dimensions are used for the pad without having to make any changes in another file, such as a structural or architectural link. If the equipment does not always require a pad, you can use parameters to control the display of the pad. Family types can be created for easy selection of pad-mounted versions of the equipment.
The key to creating pad geometry in an equipment family is to provide a reference for the top of the pad so that the equipment geometry can be modeled in the correct location and maintain a proper relationship with the pad. If you are creating a face-hosted family, the pad should be modeled so that it is associated with the host extrusion, as shown in Figure 19-10. Keep in mind that pads don’t always have a parallel top and bottom. If the roof is sloping, obviously the pad needs to follow the slope, but it still needs to create a level top surface for the equipment. In those cases, the pads can be a bit more complicated. A common approach is to create multiple extrusions within the same pad family and control which one is visible and when, through visibility parameters, based on the sloping conditions in the project.
Figure 19-10 Pad modeled in equipment family
Adding Connectors to Equipment Families
The connectors that you add to an equipment family will ultimately determine the types of systems for which that family will be available in your Revit projects. Connectors can be added for the completion of air, fluid, and electrical systems when the family is selected as the system’s equipment in your project.
In most cases, the location of connectors on equipment families is easily handled by geometry modeled specifically for the connector. However, it is not always necessary to have connector geometry. Some equipment families are simply used for equipment location, and do not need to be modeled to any level of detail. Early in the design of a project you may want to use placeholder equipment families until specified equipment can be chosen based on calculations. It is still helpful for these types of families to have connectors so that duct, pipe, and conduit can be connected and system analysis can be performed.
If you place the connectors by reference planes, you can dimension directly to the connector by selecting it and then activating the temporary dimension to the center of the connector. Once it is activated, you can associate the dimension to a parameter. This can be done only if you use the Work Plane option for placing the connector. Using the Face option constrains the connector to the center of the face so its location cannot be changed without changing the host face. Figure 19-11 shows how a Work Plane–placed connector location can be dimensioned and parametrically managed.
Figure 19-11 Connector location dimensions
In this example, if you want to keep the right and bottom edges of the connector static when the connector changes size, you would need to write a formula for the connector dimension parameter. For example, with a parameter that defines the connector width, such as SupplyWidth, the left edge of the connector can be made to stay at 0′-8″ (200 mm) from the left edge of the equipment by using a formula for the Supply Loc Horiz parameter, as shown in Figure 19-12.
Figure 19-12 Connector location using formula
When you have equipment that has several pipe connectors, it is helpful to create geometry for the connectors. Otherwise, you would have to define a reference plane for each connector unless they all connect at the same plane. With geometry used to indicate a point of connection, you can dimension and constrain the geometry, and then use the Face option for connector placement. This does not eliminate the need for dimensions or constraints; it only takes them off the connector object itself.
When you sketch a circle to create a cylinder, the point at which you draw the center can be dimensioned while you are in sketch mode. This dimension can be used for the location of the connector, as shown in Figure 19-13. The radius of the sketch can also be dimensioned and associated with a parameter for easy size adjustment. Remember, when creating circular connectors, use a circle for the sketch, not an arc that is copied/mirrored. This is because the center point of the pipe connector will snap to the centroid of one of the arcs, not that arc’s center point.
Figure 19-13 Geometry for cylindrical connector
Revit MEP 2013 was the first version to introduce the Diameter dimension. This allows you to control round extrusions and connectors with one parameter, and without the additional formulas that were required in the past.
Reference planes or lines can also be used to determine the location of the connection point geometry. This is easily done for pipe connections by activating the Center Mark Visible parameter of the circle you are sketching, as shown in Figure 19-14.
Figure 19-14 Using the parameter Center Mark Visible
While in sketch mode, the center mark allows you to align and lock the sketch to reference planes or lines used to control the geometry location, as shown in Figure 19-15.
Figure 19-15 Sketch center mark aligned to reference line
With the geometry in place, a connector can be added by using the Face option for placement.
You can adjust the connector properties to associate the size of the connector with the parameter created for the geometry diameter, as shown in Figure 19-16.
Figure 19-16 Associating a parameter with the connector diameter
You should know that the Diameter parameter is available only in Revit 2014 and higher. You can switch between radius and diameter from the Properties palette by using the Round Connector Dimension parameter (see Figure 19-17).
Figure 19-17 Changing between radius and diameter
Using the Face option is the easiest way to place connectors into a family. The direction of the connector can be easily flipped by using the blue arrows grip that appears when you select the connector. The direction arrow of a connector indicates the direction that pipe, duct, conduit, or cable tray will be drawn from the connector.
When using the Face option to manage the location of a connector parametrically, you will need to create additional geometry that gives you much more accurate control over the location of the connector within the family.
When you place connectors by using the Work Plane option shown in Figure 19-18, they may not be facing in the right direction. If you placed the connector by using a named reference plane and selecting it from the list, as shown in Figure 19-19, the blue arrows grip will not work to flip the direction. Instead, you will have to rotate the plane with which the connector is associated or redraw the plane in the opposite direction. If you are going to place connectors by named reference planes, it is probably a good idea to remember that you should be drawing your reference planes clockwise. This way, the orientation of the connectors will be always defaulted appropriately. The benefit of using the Work Plane option is that you can locate a connector anywhere on the plane. In case you created your reference plane in the wrong direction, and rotating it is not an option at this point because this would break the constrained geometry, you can still work around this limitation. Drag the reference plane grip past the other end, which will flip the orientation of the reference plane and the connector Another option is to use named reference planes, choose the Pick A Plane option, and select the hosting plane from the drafting area.
Figure 19-18 Placing connector by work plane
Figure 19-19 Placing connector by work plane using the Name pull-down
The decision of whether to use the Face or Work Plane option for connectors depends on how you want to control the location of the connector. Whatever method you choose, once a connector is placed, you can adjust its properties so that the equipment family will behave as desired in your projects.
Duct Connectors
You can select the system type of a duct connector from the Options Bar, as shown in Figure 19-20, when you click the Duct Connector button on the Create tab in the Family Editor.
Figure 19-20 Defining the System Type for duct connectors
The Global option enables you to create air systems based on flow direction when the family is used in a project. A Global connector with a flow direction of In will enable a Supply system to be created, while a connector with a flow direction of Out can be used for Return or Exhaust. Bidirectional flow gives you options for Supply, Return, and Exhaust. Fitting connectors do not have parameters to define air system behavior, and they are typically used on duct fitting families to establish connectivity.
For air systems equipment, your duct connectors should be set with the properties that coincide with the behavior of the equipment that the family represents. Figure 19-21 shows the properties of a duct connector that has just been added to a family.
Figure 19-21 Duct connector properties
Figure 19-22 Flow Configuration parameter in Duct connector properties
Figure 19-23 Connector dimensions associated to family parameters
The dimensions of a connector can be associated with a parameter by clicking the + sign grip that appears near the connector label when the connector is selected in a view, as shown in Figure 19-24.
Figure 19-24 Associating parameters with a dimension using the + sign grip
It is important to establish the orientation of the Width and Height dimensions of a connector on your equipment. Otherwise, duct or duct fittings that are connected to the connection point may not be oriented properly. Connectors located on the side of the equipment should be easy to orient and configure. The height of the connector is the Z axis (up). However, connectors on the top or bottom surface of families can be a little tricky, as there is no clear up direction. In those cases, testing the family in the project environment is best in order to see what makes the most sense. The most common way to identify the “correct” orientation is to draw a duct and make sure that you are not getting any transitions. If you are getting transitions, you need to rotate the connector and change the mapped parameters for duct height and duct width. You can rotate a connector placed with the Face option by clicking and dragging it; however, this is an inaccurate method of rotation. Using the Rotate tool allows you to set a specific angle of rotation. If you use the Pin tool to lock the location of a connector, you will also not be able to rotate it. This can be useful if you find that you are accidentally clicking and dragging the rotation of your connectors when working in the Family Editor.
Pipe Connectors
Connectors for pipes can be placed on your equipment families in the same manner as duct connectors. You can find options for setting the system type on the Options Bar, as shown in Figure 19-25, when you click the Pipe Connector button on the Create tab in the Family Editor.
Figure 19-25 Defining the system type for a pipe connector
The properties for a pipe connector are similar to those of a duct connector, except that they deal with the flow of liquid instead of air. Because liquid flows differently, there are some different choices for the same parameters you would find in a duct connector:
Figure 19-26 Properties of a pipe connector for plumbing pipe
Figure 19-27 Pipe radius formula
Electrical Connectors
There are three kinds of connectors for electrical systems—conduit connectors, cable tray connectors, and electrical connectors:
Figure 19-28 Selecting an Individual or Surface Connector from the Options bar
Figure 19-29 Conduit surface connector on the top surface of a panel family
Figure 19-30 Multiple conduits from a surface connector
When placing an electrical connector, you need to specify what electrical system type it is going to serve, as shown in Figure 19-31. Many properties of an electrical connector can be associated with family parameters for easy management and creation of family types. The Voltage parameter determines the distribution systems in your project where the equipment can be used. This must be coordinated with the value of the Number Of Poles parameter. The Load Classification parameter enables you to assign a load classification to the connector that will determine the demand factor when used in a project. Even though you can create a new load classification in the family, and it will be available in the project when the family is loaded, it is not recommended to do it that way. You should map the connector parameter Load Classification to a shared parameter Load Classification. This way, you would be able to select the Load Classification from the project. Managing your load classifications from one place (in the project) is much more efficient then managing them in every family with an electrical connector. If you create custom load classifications in your families, they will be available in your project; however, you will not be able to delete them from the project!
Figure 19-31 Defining the system type for the electrical connector
Multiple Connectors in Families
Many MEP equipment families have multiple types of connectors. Your work environment may determine the connectors that you add to equipment families. For example, if your projects contain all MEP systems in one model, you may want to have electrical connectors in your HVAC equipment families that require electricity. If you have a separate model for each discipline, there is no need to have an electrical connector on any of the Mechanical Equipment families because the connection cannot be made through a linked file.
It is possible to link connectors in a family. This is useful when you want the system behavior to pass through, from one connector to the other—for example, when you have a pipe fitting. Linking the connectors propagates system information through the fitting, so fluid flow in is related to fluid flow out of the fitting. Using the Link function is not needed for most families that contain parameters storing the fluid or air flow (Flow and Air Flow). However, the Link functionality is needed for fittings, as they don’t have those parameters, and that’s the only way to pass the flow through the fitting. You can link connectors by selecting one of the connectors and clicking the Link Connectors button on the Connector Links panel, as shown in Figure 19-32.
Figure 19-32 Linking connectors
Linked connectors will take on the Flow Configuration value of the primary connector. So even if you have a connector in the family that has a Flow Configuration set to Preset, if it is linked to a primary connector set to Calculated, the behavior of the connector in a project will be as if the connector is set to Calculated. You can tell whether connectors are linked in a family by selecting one of the connectors in the Family Editor. Red arrows will appear between linked connectors, as shown in Figure 19-33.
Figure 19-33 Linked connectors in an equipment family
The primary connector in a family is the first connector of each type added to the family, and is indicated by crosshairs in the connector graphics. Figure 19-34 shows an equipment family with multiple types of connectors. You can change which connectors are the primary ones by clicking the Re-assign Primary button that appears on the Primary Connector panel of the contextual tab when you select a connector. Clicking the button allows you to select another connector, which will become the primary for that type.
Naming connectors in a family makes it easier to understand which one you are connecting to when working in a project. You can name a connector in the Connector Description parameter in a connector’s properties. When you use the Connect Into tool in a project on a family with multiple connectors, the connectors will appear in a list with their names so you can choose the proper one.
Now that you have learned about creating an equipment family, practice some of the basic skills by completing the following exercise. No matter what your discipline of expertise, these steps will help you become more familiar with the process of creating equipment families:
Figure 19-34 Equipment family with primary and secondary connectors
Figure 19-35 Creating reference planes for the pad
Figure 19-36 Creating dimensions and parameters for the equipment in plan orientation
Figure 19-37 Creating dimensions and parameters for the equipment in elevation orientation
Figure 19-38 Creating Yes/No visibility parameter
Figure 19-39 Associating the Yes/No visibility parameter with the Pad
Figure 19-40 Creating reference planes for the equipment
Figure 19-41 Creating dimensions and parameters for the equipment in plan orientation
Figure 19-42 Creating dimensions and parameters for the equipment in elevation orientation
Figure 19-43 Configuring settings for a parameter
Figure 19-44 Placing the supply duct connector in 3D view
Figure 19-45 Placing the return duct connector in 3D view
Figure 19-46 Associating a connector parameter to a family parameter
Figure 19-47 Configuring the properties of an electrical connector
You can save this family and use it to practice techniques for creating equipment. Load the family into a test project to test its behavior and usability.
Creating Clearance Spaces
Most MEP equipment requires some sort of clearance space for safety or maintenance reasons. Modeling the clearance spaces directly in your equipment families is useful for model coordination. Because the space is part of the family, any objects encroaching on the space will show up when you run an interference check of your model. You can choose to keep the spaces visible during modeling for visual reference to avoid such interferences. Even if you choose to turn off the visibility of the spaces, any interferences will still be detected.
Figure 19-48 shows an electrical panel family with clearance spaces modeled for the front of the panel and the space above the panel.
Figure 19-48 Clearance spaces in an equipment family
You can create clearance spaces by modeling an extrusion in the family that is associated with a reference plane at the appropriate face of the equipment. You can use other reference planes to control the size of the clearance space and constrain it to the equipment. In the example of the electrical panel, reference planes were created to constrain the top of the panel so that the front clearance space will always be 6″ (150 mm) above the top of the panel. The dimension for the space height was done in the extrusion sketch, as illustrated in Figure 19-49, which shows the plan view of the face-hosted family.
Once you have modeled a clearance space extrusion, there are properties that you can apply to it for visibility, as shown in Figure 19-50. In the panel example, a unique material type was created and applied to the extrusions for their semitransparent display. This keeps them from blocking out the actual equipment when shown in a model view.
A subcategory was created for the clearance space extrusions so they can be turned off in model views without turning off the equipment category. The subcategory is given a color for the edge lines of the clearance space extrusions to stand out from other solid geometry, as shown in Figure 19-51.
You should always ask yourself the following question: “Just because I can do it, does that mean I really should do it?” In the preceding example showing you how to create a subcategory to control the visibility of the clearance separately from the rest of the geometry, it may seem like a great way to achieve what you need at the time. But as your library grows, you will find it hard to manage those custom subcategories in individual families. Creating a standard of when to create them and what to name them can help. In addition, you should consider other available options. In this case, you could assign the clearance to the Hidden Lines subcategory, which comes with most 3D-based Revit family templates. You could also use the Visibility parameter to control when it is turned on or off. Essentially, you can achieve similar functionality by taking a different route.
Figure 19-49 Clearance space reference planes in an equipment family
Figure 19-50 Associating material for the clearance
Figure 19-51 Display of the clearance extrusion in Visibility Graphics
Although having solid geometry in an equipment family to represent clearance spaces is useful for interference coordination, you may not want to have the solid geometry displayed in plan views. Model or symbolic lines can be used to represent the clearance space for plan views. The visibility of these lines can be controlled by a Yes/No type parameter or by a subcategory. Figure 19-52 shows clearance space lines in the Front elevation view of the panel family. The lines exist in the Front elevation view so that they will be visible in plan views when the panel is attached to a vertical host.
Another option for adding clearance spaces to your equipment is to create unique clearance-space families. These families should be categorized as Mechanical or Electrical Equipment families, but you could categorize them as any of the available subcategories, depending on how you want to control their visibility. In a project file with worksharing enabled, a workset could be created for equipment clearance spaces, as an option for making it easier to control the visibility of all equipment in a view. There is a downside to relying on worksets for visibility control, however, because you may also be using worksets as an option to load selected parts of the project. This can lead to confusion, not just within your company’s project team but also for those working collaboratively with you.
Figure 19-52 Lines representing clearance space in a family
Clearance space families can be face-hosted families for easy attachment to the solid geometry of your equipment families. Consider making individual families with the dimensions for each unique type of clearance, or for specific types of equipment.
The example of displaying solid geometry (the clearance) with linework can be applied to most families’ solid geometry. Displaying lines instead of geometry will improve your overall project performance with your families as Revit will need to regenerate lines instead of surfaces. This can be especially noticeable for round objects such as pipe connectors and their extrusions, because the software will try to simplify those round surfaces by breaking them down to multiple flat surfaces.
Adding Parameters and Constraints
The key to having equipment families that are usable in the early stages of your designs is to have families that are easily modified to meet the demands of frequent changes to your project model. Using parameters gives you the flexibility to change not only the size of equipment but also the values of connectors.
Three simple dimensions can define most equipment: length, width, and height. By using these parametrically, you can be confident that your equipment families occupy the space required for them in the model, even if they do not look exactly like the object they represent. Be consistent with your use of these parameters and particularly the naming convention you use. They do not need to be shared parameters unless the information is to be included in schedules. However, you could create them as shared parameters for consistent naming. Because there may be other dimensions in your families, it is best to give these parameters a descriptive name, such as Unit Length or Equipment Width, to distinguish them as the overall size. Of course, having these parameters in your families is not enough; you need to have the family geometry associated with them.
MEP equipment schedules vary in size and information, not only from one company to another but even in the same company, depending on the project standards or client demands. Mechanical equipment schedules are particularly difficult to manage without the proper use of parameters in your equipment families. The use of shared parameters is necessary for scheduling the systems information required from equipment schedules. The problem is that all Mechanical Equipment families are in one category.
To avoid having families with unnecessary parameters, it may be best to apply your shared parameters directly in the equipment families instead of using project parameters. That way, you can be sure that you have only the parameters required for the scheduling of the specific families in your mechanical equipment schedules.
Connectors have parameters that you may need to change based on the performance of your engineering systems. Creating parameters in your families with which the connector parameters can be associated allows you to change the connector values without having to open, edit, and reload your families. The main thing to remember when creating these parameters is that they must match the units of the connector parameter in order for them to be associated. For example, you cannot associate a connector’s Voltage parameter with a number or integer parameter.
For more information on parameters and schedules, see Chapter 6, “Parameters,” and Chapter 7, “Schedules.”