Within Revit, components such as beams, columns, ducts or lighting fixtures are referred to as Families. Families can be created in a separate environment known as the Family Editor or they can be created on the fly within an actual project. Families created within an actual project are called In-Place Families.
In-Place Families are used in cases in which they are not likely to move, be relocated or copied. They are particularly helpful when the geometry of the model is needed to construct the family. A single complex or blended roof form is one such example, as you want the roof to maintain relationships to other elements (like walls) in the project. In all other cases, it is best to create the family in Family Editor. This gives you the maximum flexibility to place multiple copies of the same component or to use the same component in other projects.
If more than a single instance will occur in the project, it’s usually best to create it in the Family Editor and load it into the project.
5.1 Family Types
All elements in Autodesk Revit are classified according to their category, family, type and instance.
There are three family types in Autodesk Revit: system families, standard component families, and in-place families. Standard Component families can be loaded into projects whereas system families cannot be loaded into projects. In-place families can be used to create elements that are unique to a project and not provided in family content libraries.
Categories are the most general and are subdivided into model categories and annotation categories. Model categories include beams, columns, doors, windows, and walls. Annotation categories include dimensions, grids, levels, and text notes. Families are classes of elements within a category that group elements with a common set of parameters, identical use, and similar graphical representation. Different elements within a family may have different values for some or all properties, but the set of properties are the same.
Parameters, in general, provide you the ability to define certain characteristics about an object. Parameters may be used to define properties of the solid geometry, such as length, width, and height. Parameters may also be used to define other characteristics about an object such as fluid flow, voltage, current, or fixture units. Parameters used to define aspects of a family are either Family parameters or Shared parameters.
Family parameters cannot appear in schedules or tags. Family parameters are limited to usage within the family in which they are defined. Family parameters are commonly used to define various portions of the geometry in a family. For example the table below shows several parameters that are used to calculate lengths in different portions in a duct fitting.
For example, in the _Water Heater.rfa family, the dimensional parameters were all created as family parameters based on the data found in a manufacturer’s cut sheet. Since not all dimensions were explicitly defined on the cut sheet, some liberties were made when modeling the family. When creating a family, you may want to simplify the geometry to make it easier to model, and possibly to make it more adaptable to other manufacturers.
Shared parameters provide the most flexibility, because unlike family parameters, shared parameters can be scheduled. If you have common properties that you want to use in multiple families such as the length, width, and height of components within a modular air handling unit, shared parameters let you define the parameter once, and use it multiple times. Shared parameters are also required if you want to schedule characteristics such as the voltage, motor horsepower rating, electric heat
requirements, and other such properties that are commonly found in mechanical equipment schedules.
When you are defining a parameter in a family, you have to specify whether the parameter is a family parameter or a shared parameter. If you want to schedule or tag the property, use a shared parameter.
The definition of a shared parameter exists externally to your .rvt model file in a .txt file. Since the shared parameters are in an external file, they may be used by multiple .rvt models, as well as multiple .rfa families. Only the definition of the shared parameters exist outside the model, the parameters themselves exist in the model, so there is no need to send the shared parameters file if you are sharing your model.
Note: Although shared parameters are stored in a .txt file, DO NOT edit the file directly. 5.1.1 System Families
Families that are basic to all project files are called system families. System families are built into projects and contain predefined sets of properties and graphical representations.
A system family is available in all Autodesk Revit projects. It has a standard size, configuration, and parameters for its elements.
You cannot create or load a system family into a project. However, you can modify the type parameters to create new system family types and save them in a project template for use in other projects.
You cannot delete a system family from a project. 5.1.1.1 Creating a New System Family Type 1. Select an existing system family type.
2. Edit the desired type parameters, such as line weight, color, and line pattern, of the existing system family type by clicking in the Element Properties dialog box.
3. Create a new system family type by clicking in the Type Properties dialog box.
4. Enter a name for the new system family type and select .
5. Specify the type parameters, such as line pattern and symbol, of the new system family type according to your requirements.
6. Select twice.
5.1.2 Standard Component Families
Revit’s default Imperial and Metric family libraries are located on the “L” drive under the BH-Revit\Revit09 folder.
5.1.2.1 Creating Standard Component Families See Section 5.2 for creating Standard Component Families
5.1.3 In;Place Families
5.1.3.1 Creating In;Place Families
From the Modelling menu, select Create or click Create from the Modelling tab on the Design Bar
Note: You can also click on the Options Bar when a specific tool is active, for example, the Window or Door tool. The Family Category and Parameters dialog opens.
Note: This dialog does not open when you click on the Options Bar.
Select the appropriate family category, and click .
In the family Name box, enter a name, and click .
Use the tools on the Design Bar to add components, massing geometry, and lines. When you finish creating the in-place family, click Finish.
5.2 Standard Component Family Creation
5.2.1 Standard Component Family Creation Example 1 – Water Heater
For the water heater, we will create some shared parameters to define characteristics that will be used by both the plumbing designer on plumbing schedules, and by the electrical designer when circuiting. We will create parameters for KW, Voltage, Phase, and Capacity.
NOTE: Sharing parametric information about a component, such as the voltage between the plumbing schedules and electrical connections requires that a single model be used. Using linked files is not an option.
Creating Shared Parameters
As noted above, shared parameters are defined in an external file. Shared parameters may be grouped to help you organize the parameters.
1. Open the _Water Heater.rfa
2. From the File menu, click Shared Parameters… 3. Click Create…
The practice-wide shared parameters file is located at
L:\BH8Revit\Revit09\SharedParameters\BH_Shared_Params.txt. The file may or may not be defined on the machine you are working on. You will not have write access to this file so you will have to create a project shared parameters file.
4. Browse to the project’s families subfolder location.
5. Enter the project number and project description, 123456 Example Project Shared Parameters.txt 6. Click Save
7. Click New… under Groups.
8. Enter the name Electrical, and then click OK. 9. Click New… under Parameters.
10. Specify the following, then click OK
• Name: Voltage
• Type: Electrical Potential
11. Repeat step 9 to create the following parameters:
Name Discipline Type
Power Electrical Power
Phase Common Integer
Number of Poles Electrical Number of Poles
12. Repeat step 7 to create another group called General.
13. Repeat step 9 to create the following parameter under General:
• Name: Capacity
• Discipline: Common
• Type: Integer
14. Click OK to close the Edit Shared Parameters window. Assigning Shared Parameters to your Family
1. Click on the design bar.
2. Click Add… under Parameters.
3. Under Parameter Type, select Shared parameter. 4. Click Select…
5. In the Shared Parameters dialog, select General from the Parameter group list. 6. Select the Capacity parameter, then click OK
8. Select Type 9. Click OK
10. Repeat steps 2-9 to add the following shared parameters:
Parameter Group Parameter Group parameter under Instance/Type
Electrical Number of Poles Electrical Type
Electrical Phase Electrical Type
Electrical Power Electrical Instance
Electrical Voltage Electrical Type
NOTE: The Voltage and Number of Poles properties must be set as Type parameters. If they’re not Type parameters, you can’t create a new circuit from the water heater.
11. Click OK to close the Family Types dialog Creating Parameter Formulas
The formulas defining the water heater characteristics have not been defined. In this section, the formulas will be defined.
1. Click on the design bar.
2. Add the following shared parameters:
Parameter Discipline Type of Parameter Parameter Group Instance/Type
P1 Electrical Power Electrical Instance
P2 Electrical Power Electrical Instance
3. Enter the following formulas as listed below.
NOTE: The per-phase power parameters (P1, P2, and P3) only apply to L-L single phase or three phase connections. NOTE: The if statements are structured as follows: if(conditional statement, result if true, result if false). Thus, for the P1 parameter, if Phase=3 (i.e., a 3 phase load), then the load on P1 (phase 1) is the total power divided by 3 (Power / 3), if it is not a 3 phase load (assumed to be a single phase, L-L load as noted above), then the load on P1 is Power divided by 2 (Power / 2).
4. Click OK to close the Family Types dialog. Creating Family Types
A family is a general definition of an object, whereas a type may be a specific size of object. In the case of the water heater, we will create three types for three sizes of water heaters: 50 gallon, 80 gallon, and 119 gallon.
1. Click on the design bar.
2. Click New… under Family Types.
3. For the name, enter: 100 gallon, then click OK 4. Set the values as shown below:
5. Click New… and create two more family types using the following values:
• Name: 40 gallon
6. Click OK
Mapping Parameters on Connectors
In the water heater family, we added parameters for voltage, power, phase, and number of poles. However, these properties are not yet associated with a connector. Until we add a connector, and map the associated properties of the connector to the parameters, the load information can’t be utilized in circuiting the object. We need to place an electrical connector object, and then associate the connector’s properties with the parameters in the family.
1. Click on the design bar.
2. Select the method. 3. Place the connector.
4. Select the newly placed connector, and click Properties on the Options Bar. 5. Set the Number of Poles to 3.
6. Set the System Type to Power ; Unbalanced.
10. Click in the column of the Apparent Load Phase 1 row. 11. Select P1, and then click OK.
12. Click in the column of the Apparent Load Phase 2 row. 13. Select P2, and then click OK.
14. Click in the column of the Apparent Load Phase 3 row. 15. Select P3, and then click OK.
16. Click in the column of the Voltage row. 17. Select Voltage, and then click OK.
18. Click in the column of the Number of Poles row. 19. Select Number of Poles, and then click OK.
20. Click OK. 21. Save the family.
NOTE: In this example, I opted to demonstrate how you would calculate a per-phase load, and assign the load to each phase. In the case of this water heater, I could have left the Balanced Load option checked, and instead of assigning the load on a per-phase basis (Apparent Power Phase 1, 2, and 3), I could have assigned Power to the Apparent Load parameter. Placing the Water Heater
In this example we will load and place the water heater in a sample project. Additionally, we will create a voltage specific type in the project.
1. Create a new project.
2. Set the LEVEL 1 ; PLUMBING – WORKING view active. 3. Click Mechanical Equipment on the design bar. 4. Click Load… on the Options bar.
5. Browse to and Open _Water Heater.rfa. 6. Place the water heater in the model.
7. Select the placed water heater in the model, and click Properties on the Options Bar.
8. Click
9. Select the 80 gallon type.
10. Click .
11. Enter the name: 80 gallon – 480v – 3ph 12. Click OK.
13. Set the Voltage to 480. 14. Set Number of Poles to 3.
15. Click .
16. Set Power to 12,000 W. 17. Set Phase to 3.
18. Click .
Circuiting the Water Heater 1. Create a piece of wall 2. Create a electrical panel
3. Open the LEVEL 1 ; POWER – WORKING view. 4. Select the water heater.
5. Click on the Options bar to create a new circuit for the water heater.
7. Select the panel. 8. Create a Panel Schedule Lookup Tables
Lookup tables provide a method to define parameter values using tabular data. This functionality is very beneficial because many properties can not be described based on a simple formula, or even be described using a complex formula with many nested if statements. The functionality of lookup tables is limited to defining pipe fittings, valves, and the like, where the overall geometry is directly related to the nominal size of the component.
Take for example the Pipe PVC Bend as partially shown here. For a 4” pipe elbow, the dimensions for outside radius (Radius) and the radius from the pipe centerline to the sweep radius (Center Radius) are shown. For a 2” pipe, these dimensions are Radius = 1 5/16” and Center Radius = 1 13/16”. To construct an If statement for the Radius parameter based on the nominal pipe size, it would be something like this:
if(Nominal Size = 0' 4", 0' 2 7/8", if(Nominal Size = 0' 2", 0' 1 5/16", 80' 1"))
This formula only defines the Radius if the nominal size is 2” or 4”. Imagine if there were 15 sizes as in the case of the case of this Pipe PVC Bend. The nesting of the if statement would be unmanageable.
This is where lookup tables are very handy. Instead of having to create an unruly if statement, a lookup table may be used. Lookup tables are simply .csv (comma separated value) text files that define rows and columns of information, similar to a spreadsheet. Each row essentially defines a type in a family, i.e., the size in the case of the Pipe PVC Bend.
Lookup files may be edited in Excel or Notepad. If you use Excel, make sure to specify the .csv format for the file type as shown below:
The lookup file must be stored in a specific location for Revit to be able to find the file when generating a family. This location is defined in the Revit.ini file using the LookupTableLocation setting.
Take a look at a sample .csv file opened in Excel (Pipe PVC Fitting Sizes.csv) below:
Row 1 is used for column headers which are used to identify lookup parameter names, parameter types, and parameter units. In the above figure, column C defines a parameter named PipeOD of type length in unit’s inches. Note the ## between each component in the header.
Column A is used to provide an identifier for the type. Revit doesn’t use this column, but it must exist. The column is for the user to identify each size. Also, note that cell A1 is intentionally left blank.
The Radius parameter above is calculated using a function called text_file_lookup. This function is used to lookup values in a lookup table (csv) file. The signature of the text_file_lookup function is as follows:
value=text_file_lookup(LookupTableName, LookupColumn, DefaultIfNotFound, LookupValue) Where:
Value is the result of the function
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 second column of the table (column B when viewing in Excel)
Inspecting the usage of the text_file_lookup function in the Pipe PVC Bend family can provide an understanding of how the function works. In the formula, the following parameters are passed to the text_file_lookup function:
text_file_lookup(Lookup Table Name, “PipeOD”, 4,4)
LookupTableName Pipe PVC Fitting Sizes.csv (defined in the Other group) LookupColumn “PipeOD” (when viewing the CSV file in Excel, this is column C) DefaultIfNotFound Nominal Size (in this example, 4”)
LookupValue Nominal Size (in this example, 4”)
When the text_file_lookup function is used in this case, it will lookup the PipeOD (from column C) associated with the 4” Nominal Size 0 (column B). In this case, the result value is 4.5 (column C row 11 in the spreadsheet). If we substitute 4.5 in the formula, it simplifies to:
value=0’ 0 1/8” + (4.5 / 2) = 0’ 2 3/8”
What happens if we try invalid values? It depends…
Invalid LookupTableName
The .csv file doesn’t exist
Invalid LookupColumn
The column doesn’t exist in the
Invalid LookupValue
table The result of the text_file_lookup function will be the value specified by DefaultIfNotFound
Invalid LookupValue example: Say we wanted to know the PipeOD if the Nominal Pipe Size (column B) was 5.5”, but this value doesn’t exist in the table. However, the function allows a substitution of another value, namely the DefaultIfNotFound. In the formula for this example, the Nominal Size specified as both the LookupValue and the DefaultIfNotFound. Since 5.5 can’t be found in column B, the DefaultIfNotFound = Nominal Size = 5.5 will be the result of the text_file_lookup function. Substituting this back into the formula for the Radius, we get
value=0’ 0 1/8” + (5.5 / 2) = 0’ 2 7/8”
NOTE: If you want to keep an invalid value from being used (i.e., to disallow a 5.5” valve), you can specify the DefaultIfNotFound parameter to be -1” on a property that specifies a dimension in the family.
If the following row were added to the PVC Fitting Sizes.csv, the result would be different:
value=0’ 0 1/8” + (6 / 2) = 0’ 3 1/8”
NOTE: If you modify a lookup file, you must restart Revit for the file to be re-read. Valve Lookup Table Sample
In this example, a very simple version of the valve shown here will be configured to use a lookup table to read the values A, C, D, and D1 based on the ND1 parameter.
In the _Valve.rfa family, the valve geometry and family parameters have already been created. The first task is to define the ND1 parameter on the main body of the valve, and map the ND1 parameter to the valve connectors. However, there is a catch. Revit doesn’t define curved surfaces in terms of diameter, everything is defined in terms of radius. Thus, there is a NR1 and D_Rad parameter to assign to the appropriate geometry.
It is notable that the valve will ‘know’ what size it needs to be when placed on a pipe. The valve ‘reads’ the size of the pipe, and it is inherited into the connectors’ radius property. This sample will use a parameter called NR1, then calculate the ND1 based on NR1. Then, all the other properties will be read from a .csv file based on ND1.
Creating Family Parameter Formulas
All the necessary parameters are assigned to the model dimension lines and extrusions. Now we need to create the text_file_lookup and radius formulas.