Revit MEP

Revit MEP

Monday, July 23, 2007

Best Practices for Autodesk Revit Parametric Components (Families)

Autodesk Revit Parametric Components (also referred to as Families) offer an open, graphical
system for design thinking and form making. A powerful feature in the Revit suite of products,
families help users manage data and make changes easily. This white paper examines Best Practices relating to Autodesk Revit Families.

Revit Parametric Components are called families because one family type can contain many variations. A family can be anything in Autodesk Revit software, from a table to a window to a two-dimensional representation of an anchor bolt. Any item that may need to be represented in a project can be created in a family.

A large number of predefined families are included with Revit. Manufacturers are creating Autodesk Revit Families that are available from their websites or included on product disks. Despite the availability of large family libraries, users sometimes need to create custom components for a project. This can be easily accomplished using the Autodesk Revit Family Editor; a simple graphical interface that allows users to model any object and apply the power of parametrics to that object.

Users do not need to know any programming language to create content for Autodesk Revit. Family creation is made easy through the use of templates, which are provided with the software to help users get started with families. These templates allow Revit users to focus on the geometry of the object, as they contain all the programming necessary “behind the scene”.

Autodesk Revit Families are extremely powerful because they are driven by the Revit parametric change engine. The parametric change engine enables a change made to a family to propagate throughout the entire project. Once created, a family’s parameters remain exposed and can be edited directly within the Revit project. Ultimately, it is the parameters that drive a family’s geometry. Mathematical formulas can be used in these parameters to create complicated geometry, or to drive parameters in a user defined solution (for example, using a formula in a window family that always makes the width of the window twice its height).

Revit Families also feature nested families - one family residing in another family. For example, a user might nest a door hardware family into a door family. Nested families add a level of strength and capacity to the process. Users can create a single family file that includes dozens of different options.

This paper explores the use of families in Autodesk Revit - from the basics of the Family Editor to advanced topics and considerations when using families - all of which will provide the reader with a Best Practices approach to creating parametric component families in Revit.

Design Considerations
Before creating a family in Revit, users should consider the following questions regarding their intended use of a family:
  • What size(s) does this family come in?
Is this a custom piece of furniture that only comes in one configuration, or is this a window that is available in several preset sizes? Perhaps, this is a bookshelf that can be built in any length from between 2’-0” to 5’-0” wide. This is an important point to consider before building a family, as it will dictate decisions that need to be made in the near future.
  • How should this family appear in different views?
Is this an object that should be seen from plan view, elevation view, and/or sectional views? Maybe this is a 2D object that should only be seen in plan or elevation. In any case, the way that this object should appear in views will determine how to define its visibility.
  • Does this family require a host?
Is this family typically attached to another design element - a wall, or maybe a ceiling? Possibly it is a roof mounted mechanical unit. How this family is hosted (or what it does or does not attach to) will determine which template file should be used to start the family.
  • How much detail should be modeled?
Is this family an electrical wall outlet that will only be seen in interior elevations from a distance, or is it a door family with raised panels and a sidelight that will be seen in an interior rendering of the project? This determination will help decide how much detail to provide in the family.
  • Where should the origin point be?
Is this a column family that would use the center of the circular base as the insertion point, or is this an accessible toilet that must always be placed 18 inches off the adjacent wall to meet code? This decision will help users when they start placing geometry.
Recapping these important first questions to consider before creating a family:
  1. What sizes does the family come in?
  2. How does this family appear in different views?
  3. What hosts might this family be attached to?
  4. How detailed should this family be?
  5. What is the origin point of this family?
Creating a New Family
Once the basic questions listed above are considered, a user is ready to create a new family. There are three types of Autodesk Revit families:
  • System families,
  • In-place families, and
  • Standard component families.
System families are predefined within Autodesk Revit, and comprise the basic building components such as walls, floors, and roofs. Users can create their own versions of system families by duplicating an existing version and modifying its properties. Users cannot create new system families.

In-place families are components that are created specifically for a single project only. They are created from within the current project, and cannot be used in other concurrent or future projects. The best time to use an in-place family over a standard component family is when creating a component unique to a specific project. For instance: a reception desk in the lobby of a law firm may have a very unique design featuring curving shapes requested by the client and finishes unique to that lobby. In this situation, an in-place family should be used because there is little chance that this custom-designed piece will be repeated in another project.

Standard component families are the most common families in Autodesk Revit, and are the focus of the remainder of this paper. Standard component families can be placed in project template files so that they preload with each new project, or they can reside in libraries to be loaded on demand.

While working in the Family Editor, users can: 1) open an existing family and modify it to suit their needs, or 2) start a new family using the appropriate template. To start a new family, choose the File pull down menu and then select New >> Family.

TIP: To save time, users should duplicate and modify a similar existing family to suit their needs instead of starting a new family from a template.

Templates
Templates for family creation are supplied with Autodesk Revit. The various templates cover a broad range of possibilities from 2D annotation objects to 3D roof-based spot lights. Each template has been pre-configured to aid in the construction of a specific object type.

Figure 1
Autodesk Revit includes many templates to create families of parametric components.

Some templates have a combination of reference planes and pre-defined parameters to guide users during creation. Family templates for hosted objects will contain a host to build from. For example, in roof-based families a portion of a roof will be exposed in the template for the user to reference as a base. Still other templates have text notes embedded in them that may define the interior and exterior faces of a wall.

Another item that is found in some family templates are controls. Controls placed in families allow the user to change the position of the geometry in a family after it’s loaded into the project. An example of these controls can be seen in a door family, where controls allow the swing and the hinge-side of the door to be reversed.

Figure 2
The template for a door family includes controls to easily reverse the swing and hinge-side of the
door..

To create a family based on a template, browse the list of templates, and choose the one most appropriate to the object being built. If the object does not fall into a specific category, the Generic Model template may be the best choice. After picking the template, the user is ready to launch the Family Editor.

Family Editor
The Family Editor is built into Revit, and is launched by opening an existing family (those with an RFA extension) or by starting a new family from within Revit. The Family Editor launches within the Revit application, and employs the same user interface. The Design Bar on the left of the drawing window changes to a unique set of tools for family creation, and the Project Browser updates to show specific views depending on template selection.

Figure 3
The Family Editor user interface matches the general Revit user interface.

At a minimum, the drawing window will display two crossing Reference Planes - and possibly some dimensions, text, and notes to the designer. The crossing Reference Planes are important because they define the origin of the family. It’s a Revit Best Practice to leave these existing items (preloaded from the family template) alone. Users should not move or delete these items, as they play an important role in the family. In fact, there are some items (such as dimensions) in some family templates that cannot be deleted by the user - underscoring the general principal that if an item is in the template when it's first opened, it should be left there.

Reference Planes
A common mistake among users is to start adding objects and solids at this point. While it’s almost time to start modeling, there is still some more preparation that will later serve a significant purpose. After opening the template, the first thing a user should do - before creating model geometry - is use Reference Planes and Reference Lines to create construction lines for the geometry that will be added later.

Start in a view that best fits the family being created, such as a plan or elevation. Reference Planes should be used as datum lines that extend beyond the edges of the visible drawing area. Drawing a reference plane (often called ref planes) in a plan view will also cause that same reference plane to be seen in a crossing elevation or section view, because it is literally a plane that extends in a horizontal and vertical direction simultaneously.

Figure 4
Reference Planes should be defined before creating geometry.

Unlike reference lines, reference planes do not have “defined” endpoints. They consist of two associated planes: one parallel to the view and one perpendicular. Ref Lines can be used in rotational control of families, because the endpoint can be constrained. Reference Lines and Planes can be renamed, so that users can easily refer to them at another time.

Creating Parameters
Reference planes that have been laid out should align with the major axes of the planned geometry. Users should begin to add dimensions to specify parametric component geometry. Start by thinking how the object should be controlled. Height, width, and depth are three dimensions often used in families, and these dimensions and parameters are pre-loaded with many of the templates. Users may need to add more dimensions to describe other geometry - for instance; trim, width, and depth are common in a Window family.

Once the dimensions have been added for the major pieces, users can start adding labels to dimensions, creating parameters. There are two categories of parameters: instance parameters and type parameters. Changing an instance parameter affects the parameters of a single entity (or instance) of an object. Changing a type parameter affects all parameters of the same type.

If there are several instances of the same family loaded into a project, and each individual representation of that family needs to be a different length, then use instance parameters. For example, consider two counter tops in the same project. One instance of the counter top is placed and its length (an instance parameter) is set to 5’ – 0”. A second counter top is placed and its length (an instance parameter) is set to 5’ – 5 ¼”, spanning the distance between two walls. The instance parameters easily allow these two counter tops to be set to different lengths. Instance parameters have another unique characteristic: dimensions that are controlled by instance parameters will display shape handles when selected in a Revit project. Shape handles allow the user to click and stretch the shape of a family to a new position or size by using the mouse.

Figure 5
Instance parameters display shape handles (shown here in blue), a convenient way to stretch the shape of a family.

Type parameters control families at a higher level. They control the predefined types of families used in the project. Use type parameters to load an object repeatedly in a project and control those repeated objects as if they were one. For example, consider a door family. A users places a door repeatedly in the model as a 6’-8” tall door, but later decides to change the height of all the doors to 7’-0”. Changing one type parameter will cause all of these doors to update their height simultaneously.

To add a parameter, click on a dimension then add a label. Once the dimension is labeled, it becomes a parameter. In the Options Bar, a drop down list of available parameters will appear. If the parameter needed is not available, select Add Parameter. When adding a new parameter, specify whether it's an instance or type parameter. After adding the parameter, the dimension changes to include the parameter name and the dimensional length.

Figure 6
Add a new parameter using the Revit Family editor.

As parameters are created, they are added to the parameter list in the Family Types dialogue box (selecting by clicking Family Types in the Design Bar). This Family Types dialogue box contains several key areas. Most noticeable is the list of defined parameters in the main window, arranged into logical parameter groups (Construction, Dimensions, and Identity Data in the example in Figure 7). During creation or editing, users can assign which category is assigned to a parameter.

Figure 7
Family parameters are listed in the Family Types dialog box.

On the right side of the dialog box, users can create new Family Types, or rename or delete existing Family Types. Revit features Family Types to predefine a set of parameters - making a particular “type” of object.

Returning to the door family as an example, several door types can be defined in this dialog box. One type might be a “3068” door (a door that is 30” wide and 6’-8” tall). Another type might be a “3668” (36” wide and 6’-8” tall). A user could then define a “3070” and a “3670” door in this dialog box. Family Types allow Revit users to quickly define a multitude of sizes and combinations of an object, based on just one family and one set of parameters.

The lower group of three buttons in the Family Types dialog box is specifically for parameter creation; Add, Modify, and Remove. Click the Add button to launch the Parameter Properties dialog box to add a parameter to this family.

Notice the Parameter Types section of this Parameter Properties dialog box (see Figure 8). There are two types of parameters available in Revit: family parameters and shared parameters. A family parameter is specific only to this particular object and its value cannot appear in a schedule or tag. A shared parameter can be shared across multiple families and projects. Its value can appear in schedules and tags, and can also be exported out to ODBC. Family parameters are stored within the family file, whereas shared parameters are saved in an external text (TXT) file, typically on a network where other users can access the text file to use the shared parameters.

Figure 8
Family parameters are listed in the Family Types dialog box.

Parameter data for a family parameter is entered in the Parameter Properties dialog box.:
  • Name: The parameter's name is completely left to the user. It’s a Revit Best Practice to keep these names simple, short, and concise whenever possible. When using formulas (described later in this paper), these parameter names will have to be retyped exactly as entered here.
  • Discipline: A parameter's discipline can be set to Common or Structural.
  • Type: This drop-down list contains several pre-defined categories for the value of the parameter, such as Text or Number, or Yes/No.
  • Group Parameter Under: This area allows users to classify the parameter in a logical grouping. When the family appears in a project, the parameters are listed in groups of common elements to make it easier to enter the data by logical groups.
  • Instance and Type. Select the radio buttons that best fits the parameter.
Once these decisions regarding a parameter are made, enter the necessary data into the fields in this dialog box, and click the OK button, which returns the user to the Family Types dialog box. The user will now see the new parameter listed under the Parameters heading, and organized into the groups defined in the previous step.

To change the parameter, users can click the Modify button, or remove the parameter from the family entirely with the Remove button. Continue to add additional parameters by repeating the steps above to complete the design of the family.

Testing the Family
Before finishing a family, it’s very important to "flex" or test the model - to check that the elements created are reacting as expected when parameters change. Users should develop a habit of flexing the model repeatedly when creating families, especially after adding parameters.

To flex the model, click the Family Types button in the Design Bar. In the Family Types dialog box, the various parameters of the object are listed. Pick a parameter, and change the dimension value associated with it, then click Apply and see how the model changes. The intention is to see if the reference planes have moved to a new position as expected. Change the parameters to a range of numbers (clicking Apply each time) to test a range of values from which the family would normally operate - to assure the planes are moving to the correct lengths and dimensions.

Occasionally a user will see an error such as “Constraints not Satisfied.” This usually means that the parameter is trying to control a part that is already constrained by another parameter. As more parameters are added to the model, be sure to flex multiple parameters to test them. For instance, if flexing the width works well, then set a new width, and flex the height. Try different combinations to assure all is moving as expected.

Once a user is satisfied that reference planes, dimensions, and parameters are all working as expected, it's finally time to add some real geometry in the form of Solids and Voids.

Adding Geometry
There are several choices for creating geometry in Revit: Extrusions, Blends, Sweeps, and Revolves. These four geometry types can either be solids or voids. The type of geometry used depends on what is being modeled. For example, in a door family, the door panel itself could be an extrusion of a rectangular shape. The door frame could be a sweep - a profile in the shape of the door frame would be swept along a path defined by the sides and top of the door opening. The door knob might be a revolve. A void-blend could be used to cut the raised panel into the surface of the door panel.

The method for adding geometry is similar for all geometry types. The rest of this section will use extrusions as an example. From the Design Bar in the Family editor, choose Solid, then Extrusion. Revit will switch to Sketch Mode, and the user will have two options for sketching a shape. The first option is to draw the shape using tools from the Options Bar such as Line, Arc, Circle, Polygon, etc. The second option is to use the Pick tool from the Options Bar to pick reference planes, lines, or other existing geometry. As the user begins to draw or pick, magenta sketch lines appear. These lines could be drawn over the top of the reference planes, or more loosely sketched and then moved into alignment with the reference planes. The key is to make these sketch lines lock to the reference planes.

Using the Pick tool, the user has the option to lock the sketch lines upon placement. Blue padlock symbols will appear when lines can be locked to other geometry, lines, or reference planes. To lock and unlock relationships, simply click the lock symbol to toggle it opened (unlocked) and closed (locked). Sketch lines can be moved using a 'press and drag' technique; clicking on the line and moving the mouse while holding down the mouse button. When using this method, notice that sketch lines will automatically snap to reference planes and other relationships while being moved. Moving a sketch line off and back onto a reference plane will cause the lock symbol to appear, allowing the user to choose to lock it or not. The Align tool also allows the user to create constraints using the lock symbols.

TIP: When flexing the model, move the dialog box to the side of the screen, to better see the family in the drawing area.

After sketching the shape, and locking the sketch to the appropriate reference planes, the Extrusion properties in the Design Bar are used to define the thickness of the extrusion. This number can also be set in the Options Bar. When satisfied, click Finish Sketch and the geometry will appear. Flex the model again from various views, including 3D, to make sure the geometry behaves as expected. If it doesn’t, highlight the geometry and stretch it, using the blue shape handles that appear, to align and constrain to a reference plane.

Formulas
Formulas are one of the many powerful aspects of Revit Families - used to control families in a variety of ways. Formulas can use logic such as IF statements (IF the width is 1’-0”, set the height to 4’-0”) as well as mathematical expressions. They can be used to control Yes/No parameters, and to control parametric arrays.

Formulas are typed directly into the Family Types dialog box, where all of the parameters for a family are listed. Simply place a formula into the cell adjacent to the value, beginning with an equal sign. When entering a formula, abbreviations (such as +, *, sin, and so forth) can be used.

The following are valid formula abbreviations:
+ Addition
- Subtraction
* Multiplication
/ Division
^ Exponentiation, i.e. x^y = x raised to the power of y
log Logarithm
sqrt Square root, i.e. sqrt(16)
sin Sine
cos Cosine
tan Tangent
asin Arcsine
acos Arccosine
atan Arctangent
exp e raised to an x power
abs Absolute Value

Referring back to the family parameters listed in the Family Types dialog box in Figure 7, notice that there are parameters for height and width. In the figure, the height = 4’-0” and width = 3’-0”. To set the width of this family to always be one half the height, click in the Formula column of the width parameter and enter “=Height/2”. The values are case sensitive, and must be typed exactly as they are defined. This is why it is important, when naming parameters, to be concise about the name chosen (as described above in the Creating Parameters section). Test how formulas work by changing the value of height, and watching the width value change automatically.

There are many complex mathematical functions that can be used. Logical functions include IF, AND, OR, and NOT statements. Formulas can also use greater than/less than signs (< >). Experimenting with formulas will allow users to create some very powerful Revit Families, such as a book shelf that automatically adds support brackets as the length of the shelf increases or a window family where the muntins turn off when the window size decreases beyond a defined limit.

Saving a Revit Family
When the Revit Family is ready to be used in a project, save the family with an appropriate name, and store it in a location that is easy to find. A Best Practices tip is to organize family content into a system that mimics the Revit Library. This makes it much easier for users to find what they're looking for.

To load the family into a project, select File >> Load From Library >> Load Family, and then browse to the saved file and select it. Alternately, for many component types, when the tool is selected, a Load button becomes active in the Design Bar.

Create a keyboard shortcut to automatically open the Load Family dialog box, or click the Load button in the Options Bar for many component types such as doors and windows when the tool is selected in the Design Bar.

Once loaded into a project, the family can be moved and copied as needed. To edit the family, simply select the object, and click the Edit Family button in the Options Bar. This will launch the Family Editor and open the selected family. When finished editing, the family can be loaded directly back into the project by clicking the Load into Project button in the Design Bar. Saving the family from the Family Editor using this method will overwrite the file that was originally the source for the object in the project. Simply modifying and reloading without saving will update ONLY the project into which the family is loaded.

There are many resources available if users need assistance or are have problems with Autodesk Revit families. First, file a Support Request through the Help Menu in Revit. This puts users directly in touch with the Autodesk Revit team for assistance. The Revit Forums at AUGI.com are also an invaluable resource. Membership is free and there are thousands of people from around the world logged in 24 hours a day - ready and willing to help.

Summary
Autodesk Revit Families and the Family Editor are extremely powerful. One of the best ways to become familiar with the Family Editor is to open an existing family - investigate how it was built and what parameters or formulas were used. Start by watching the effect of changing parameters. After becoming comfortable with existing families, try making a new family. Users will soon come to realize and appreciate the full power of the parametric technology inherent in Autodesk Revit.

Final Review
Steps to create a family in Autodesk Revit:
  1. Select the appropriate family template.
  2. Lay out reference planes to aid in drawing component geometry.
  3. Add dimensions to specify parametric component geometry
  4. Add labels to dimensions to create type or instance parameters.
  5. Flex the new model to verify correct component behavior.
  6. Add geometry in Solids and Voids, locked to reference planes.
  7. Specify 2D and 3D geometry display characteristics with sub-category and entity visibility settings.
  8. Define family type variations by specifying different parameters.
  9. Save the newly-defined family, then load it into a new project and see how it performs.

Revit MEP Family Editor

Creating a Family requires careful thought of not only the geometry, but also understanding of how the settings in Family Editor affect the Family. In most cases, it is easier to start with an existing Family that is close to what is required. This way, most of the Family settings are verified through Revit MEP pulldown menu Settings=> Family Category and Parameters, and the focus can be on the geometry.

Starting with an existing Family still has its challenges. The way a part flexes as geometric parameters are modified often times has more to do with the process used to create the Family, not necessarily the end result. If the Family you are creating is very similar to an existing Family, you may want to create multiple Types instead of another Family. However, don’t get too carried away. It is generally easier to create multiple Families instead of trying to create the ultimate Family with Types that address all conditions.

Connectors

One of the primary differences in creating content for Revit MEP and other Revit content is the concept of connectors. All Revit MEP content will need to have connectors added to it for it to be useful.

There are three basic types of connectors (referred to as domains) that can be added to a family, and two different methods for placing the connector. Making the correct selections in this dialog is critical to the content working correctly, as once this selection is made, it cannot be changed. Any connector that is placed must be deleted and re-added to change the domain or the placement method.

  • HVAC connectors are associated with ductwork, duct fittings, and other elements that are part of the air handling systems for the building.
  • Electrical connectors are used for any type of electrical connections within the building. Currently electrical connectors are more “logical” connectors than physical connectors, as the application doesn’t currently support the “3D” modeling of elements like conduit, cable tray, or bus duct, but is rather a logical model of the loads within the building.
  • Piping connectors are used for piping, pipe fittings, and other elements that are meant for transmitting liquids, steam, gases and other fluids within the building.

Connector Properties

The discipline assigned to a connector determines the connector’s properties. The following tables show the different connector parameters, by property group, for each discipline and a brief description of their functionality.

Electrical

Constraints


Edge loop centered

Connector placement method (read only)

Graphics


Size on screen

How large the connector shows inside family editor.

Electrical – Loads


True Load Phase 3

Enabled if Balanced Load is False, and System Type is Power, and Number of Poles >3.

True Load Phase 2

Enabled if Balanced Load is False, and System Type is Power, and Number of Poles >1.

True Load Phase 1

Enabled if Balanced Load is False and System Type is Power.

True Load

Enabled if Balanced Load is True and System Type is Power.

Power Factor

Enabled if Balanced Load is False, and System Type is Power, and Number of Poles >3.

Apparent Load Phase 3

Enabled if Balanced Load is False, and System Type is Power, and Number of Poles >2.

Apparent Load Phase 2

Enabled if Balanced Load is False, and System Type is Power, and Number of Poles >1.

Apparent Load Phase 1

Enabled if Balanced Load is False and System Type is Power.

Apparent Load

Enabled if Balanced Load is True and System Type is Power.

Voltage

The voltage specified on the connector. Only enabled if the System Type is Power.

System Type

Data, Power, Telephone, Security, Fire Alarm, Nurse Call, Controls, Communication

Load Classification

HVAC, Lighting, Power, Other

Power Factor State

Lagging, Leading

Balanced Load

True or False

Number of Poles

1, 2, or 3

Identity Data


Index

A unique identifier for a connector in a family (read only)

Primary Connector

True or False (read only)

Connector Description

A description of the connector for the user’s reference.

HVAC

Constraints

Edge loop centered

Connector placement method (read only)

Angle

Used for adjustable angle families (such as elbows and adjustable tees) to “drive” the angle value into the family from connected components

Graphics

Size on screen

How large the connector shows inside family editor.

Mechanical

Flow Factor

Only editable if the Flow Configuration is specified as “System”. Percentage of the system flow attributed to this connector.

Loss Coefficient

Loss Coefficient is only editable if Loss Method is specified as “Coefficient”.

Flow Configuration

Calculated, Preset, System

Flow Direction

In, Out, Bidirectional

System Type

Supply, Return, Exhaust, Other, Undefined.

Loss Method

Not Defined, Coefficient, Specific Loss

Mechanical – Airflow

Pressure Drop

Enabled if Loss Method is Specific Loss

Flow

The amount of air flowing at this connector.

Dimensions

Shape

Rectangular or Round

Height

The height of the connector if the Shape is defined to be rectangular.

Width

The width of the connector if the Shape is defined to be rectangular.

Radius

The radius of the connector if the Shape is defined to be round.

Identity Data

Index

A unique identifier for a connector in a family (read only)

Primary Connector

True or False (read only)

Link Connector Index

The index of the linked connector, -1 if none. (read only)

Connector Description

A description of the connector for the user’s reference.

Piping

Constraints


Edge loop centered

Connector placement method (read only)

Angle


Graphics


Size on Screen

How large the connector shows inside family editor.

Mechanical


Fixture Units

Enabled when System Type is set to Sanitary or Domestic Hot/Cold Water, and Flow Configuration is set to Fixture Units.

K Coefficient

K Coefficient (K Factor) is only editable if Loss Method is specified as “K Coefficient”.

Flow Factor

Only editable if the Flow Configuration is specified as “System”. Percentage of the system flow attributed to this connector.

Flow


Pressure Drop


Flow Configuration

Calculated, Preset, System

Flow Direction

In, Out, Bidirectional

Loss Method

Not Defined, K Coefficient from Table, K Coefficient, Specific Loss

Allow Slope Adjustments

True or False

System Type

Undefined, Hydronic Supply, Hydronic Return, Sanitary, Domestic Cold Water, Domestic Hot Water, Other

K Coefficient Table


Dimensions


Radius


Identity Data


Index

A unique identifier for a connector in a family (read only)

Primary Connector

True or False (read only)

Link Connector Index

The index of the linked connector, -1 if none. (read only)

Connector Description

A description of the connector for the user’s reference.

System Types

When a Revit MEP component that is not a member in a system is selected in a building model, the Options Bar displays create system buttons. The specific buttons depend on the component and the type(s) of connectors in the family. If there are multiple connectors of the same type and you want to connect to a specific connector, you can right-click on the connector control or grip to create the appropriate type.

Electrical
When a component with an electrical connector is selected, the Options Bar displays one or more of the following buttons, which allow you to create a specific electrical system (from left to right: Power, Data, Telephone, Fire Alarm, Nurse Call, Communication.

Duct
When a component with an Duct connector is selected, the Options Bar displays one or more of the following buttons, which allow you to create a specific HVAC system (from left to right: Air Supply, Air Return, Exhaust).


Pipe Connector
Pipe connectors are used with hydronic systems, plumbing systems, fire protection systems. When a component with a hydronic pipe connector is selected, the Options Bar displays one or more of the following buttons, which allow you to create a specific hydronic piping system (from left to right: Supply, Return, Other.


When a component with a plumbing (pipe) connector is selected, the Options Bar displays one or more of the following buttons, which allow you to create a specific electrical system (from left to right: Sanitary, Domestic Hot Water, Domestic Cold Water, Other).


When a component with a fire protection (pipe) connector is selected, the Options Bar displays one or more of the following buttons, which allow you to create a specific electrical system (from left to right: Wet Sprinkler, Dry Sprinkler, Other).


Load Classifications
Revit MEP maintains information about loads associated with the rooms in a project. As devices and equipment are placed in rooms, Revit MEP keeps track of the loads based on load type: HVAC, Lighting, Power, Other. The loads associated with the room can be view in the Element Properties for each room, and displayed in schedules.

Connector Placement

Connector placement options allow you to specify two basic connector placement methods:

  • Place on Face - This option (Edge loop centered=true) will maintain its point at the center of the edge loop. In most cases this is the preferable method for placing a connector. Typically the Place on Face option is easier to use, and is suitable for most cases.
  • Place on Work Plane - This option allows placement of the connector on a selected plane. For many cases it would be possible to imitate the place on face option by specifying a plane and using dimensions to constrain the connector to the desired location. However, this method generally requires additional parameters and constraints to be used effectively.

Hosts

Objects that are placed in a model are hosted by other elements. Hosting elements include ceilings, floors, roofs, and walls, as well as lines, and faces. Even elements that aren’t hosted by one of these elements are still hosted by the level that they reside on.

When you are creating a family from a template, it is important that you consider what type of hosting behavior you want your family to have. For example, you may intuitively think that a new light fixture should be ceiling hosted. However, there may be cases where you want to use that family in a wall mount configuration, or even freely suspended. You can’t change the hosting of a family once it is created; the hosting setting is hard-set based on the template from which the family originated. Plane hosting provides the ability for the family to be hosted by walls, floors, or ceilings, and provides a high level of flexibility. Plane hosted elements will even move with their hosting elements through linked models. Non hosted families are actually hosted by the level they are inserted on and provide the ability for the element to be placed anywhere. Their height is defined relative to their level, but there is no association established with elements, linked models or otherwise.

When using linked files, only face hosted families will be able to be hosted by the linked file's geometry.

Templates

As described above, the hosting of an element is defined based on the template that is used when the family is originally created. Templates also define other specific characteristics of the family such as if it is an annotation family, a model family, a titleblock family, or a profile family. Additionally, in some cases, the template also defines particular characteristics of how the family works, such as linear versus spot lighting characteristics.

Remember, you can’t change these characteristics after you have created the family, i.e., you can’t turn a linear lighting fixture into a spot lighting fixture, or redefine an annotation symbol to be a model element. You have to start with the appropriate template.

Lookup Tables

Lookup tables can be used to define parameter values in an external file. This is beneficial when you have multiple part sizes that are based on a table, but don’t want to create a separate family type for each size.

Revit provides a text_file_lookup function that can be used to read the necessary values from a comma separated values (.csv) file. The location of such files are defined in the Revit.ini file:

LookupTableLocation=C:\Documents and Settings\All Users\Application Data\Autodesk\Revit Systems\LookupTables

The signature of the text_file_lookup function is as follows:

result=text_file_lookup(LookupTableName,LookupColumn,DefaultIfNotFound,LookupValue)

Where:

result is the returned value

LookupTableName is the name of the CSV file to lookup.

LookupColumn is the name of the column from which the result value is to be returned

DefaultIfNotFound is the value that will be returned if LookupValue is not found.

LookupValue is the value to find in the first column of the table.

CSV File Structure

The first row of values in the CSV file is for header information, to describe the contents of subsequent columns. The headers are of the format ParameterName##ParameterType##ParameterUnits

Acceptable parameter types are: NUMBER, LENGTH, AREA, VOLUME, ANGLE, and OTHER

For example, a header have the following header: TotalArea##AREA##INCHES to represent the total area in square inches.

Parameter Mapping

Many properties of objects, such as the depth of an extrusion and the voltage of a connector, can be mapped to a family or shared parameter. This provides flexibility to the family; the associated property’s value may be defined on an instance or type basis, and not be set to one specific value. Parameters are mapped by clicking the small button in the = column in the properties window of the object. The example below shows that the Power Factor and Number of Poles are currently NOT mapped to a parameter, whereas the Apparent Load Phase 1 and Voltage ARE mapped to a parameter.

Category

When a family is created, multiple variables affect its behavior within Revit. The Family Category and Parameters provide the primary means by which Revit ‘knows’ what an object is. When in Family Editor, the Family Category and Parameters settings are found in the Settings menu. Depending on the Family Category, different Family Parameters apply. The following matrix lists each Family Type, and the applicable Family Parameters.

Family Category

Family Parameter

Work Plane-Based

Always Vertical

Behavior Type

Part Type

Maintain Annotation Orientation

Shared

Air Terminals

P

P

P

P


P

Communication Devices

P

P



P

P

Data Devices

P

P



P

P

Duct Accessories

P

P

P

P


P

Duct Fittings

P

P

P

P


P

Electrical Equipment

P

P


P


P

Electrical Fixtures

P

P


P

P

P

Fire Alarm Devices

P

P



P

P

Generic Models

P

P




P

Lighting Devices

P

P



P

P

Lighting Fixtures

P

P




P

Mechanical Equipment

P

P

P

P


P

Nurse Call Devices

P

P



P

P

Pipe Accessories

P

P

P

P


P

Pipe Fittings

P

P

P

P


P

Plumbing Fixtures

P

P

P

P


P

Security Devices

P

P



P

P

Telephone Devices

P

P



P

P


Behavior Type – See the section titled Behavior Types in this document.

Part Type – See the section titled Part Types in this document.

Part Types

Each Part Type provides additional sub classification of Family Categories for two basic functions.

  1. you to replace a family of one category with any other family of the same category. However, there are times when this is not appropriate. For example, for fittings it would not be valid to replace a cross with a transition. So there is a level of filtering built into the Type Selector for Revit MEP.
  2. To determine the part type family. The ASHRAE Duct Fitting database is integrated with Revit MEP. This allows calculating fitting losses based on a loss table. To accurately look up the correct fitting in the database, the part type must be defined.

If a Family Category provides a Part Type parameter, the Part Types available depends on the Family Category. The available Part Types are listed below.

Family Categories

Part Types

Air Terminals

Duct Accessories

Duct Fittings

Mechanical Equipment

Pipe Accessories

Pipe Fittings

Plumbing Fixture

Damper

Duct Mounted Equipment

Elbow

Entry
Exit

Equipment

Fan and System Interaction

Hood

Junction

Obstruction

Transition

Undefined

Valve

Electrical Equipment

Electrical Fixtures

Data Panel

Normal

Panelboard

Switch
Junction Box

Switchboard

Transformer

Behavior Types

The specification of the Behavior Type has a couple different effects. One effect is that the way the part behaves when placed and when move. The other effect is that behavior specific Family Parameters will be added to the Family. For example if the behavior type is specified as Inline Eccentric, additional Parameters are added to the family to control the “offset” between the two different connectors (both horizontally and vertically).

Invalid Behavior Type

Bend elbows, and other fittings that may behave like elbows

Branch similar to a junction, where more than 3 segments intersect

Eccentric Inline causing an “offset” to the centerline of the segments

Inline maintains position “along the curve” of the segments

Intersection

Normal no specific behavior

Orient to Center Line constrain to the centerline of the segment

Orient to Object constrain to the face of the segment

Break Into break the segment, and act as “inline”