You can load instances of families in other families to create new families. By nesting existing families inside other families, you can save modeling time.
By linking family parameters, you can control the parameters of families nested inside host families from within a project view. You can control either instance parameters, or type parameters. In the Air Dryer family, I created a type parameter to control the nested ball valve family inside of it.
In order to link parameters, they must be the same type. For example, link a text parameter in the host family to a text parameter in the nested family. In the Air Dryer family I created, they both share the same Family Type Parameter. So when I change the family type of the Air Dryer, it changes the family type of the ball valve.
You can link a host-family parameter to more than one nested family parameter of the same type. Also, you can link this parameter to multiple nested families. In this example, there are two nested ball valve families that are linked and sized by one parameter.
The following is an outline for how I created a family with Parameter Links. For detailed information about loadable families, see The Families Guide.
In my air dryer family, I first created some reference planes, (as all new families should be created.) Make sure to label the reference planes.
Next, I created various solid extrusions, dimensioned them, and then labeled the dimensions to type parameters. Later I can enter various dimensions that I want to use for the multiple sizes of air dryers I want to create. In this case, I wanted six air dryers. I flexed the reference planes and extrusions by putting in a couple values into the type parameters I created and made sure the reference planes and extrusions all moved correctly.
For this family, I also needed to create a sweep to represent the pipe connecting the tanks. The pipe size would vary with the size of the host family, so I created a connection radius parameter which would control the pipe profile diameter of the sweep, and diameter of the pipe connector.
Now for the Parameter Link, which is what this article is about. I loaded the ball valve family as a nested family into my air dryer family, and inserted the two ball valves on my sweep representing my pipe using reference planes. There are six different air dryer sizes that I was creating, and as the air dryer gets larger, so do the pipes and the two ball valves. 
The pipes already were flexing from the connection radius parameter I created, but the ball valves had to be tied to a family type parameter. The result would be with each different air dryer type, a different ball valve type would be used. This is done by selecting the nested ball valve family, and click on "Add Parameter".
In this case, I made the family type parameter a type parameter, and put it in the Dimensions Group. Then just add a couple pipe connectors and one electrical connector, changed the parameters on the connectors, and we're almost done.
With my six air dryer family types I created, I now just had to enter data. To make the parameter link complete, I assigned the smallest air dryer family to the 3/4" ball valve family; the next air dryer family size to the 1" ball valve family; the next family size to the 2" ball valve family; the next family size to the 3" ball valve family; and so on...
As you can see, you can build some complex families by reusing some existing families and nesting them. This can save you a lot of time. But the point is that nested family types can be controlled by creating the correct parameter.
Just remember not to over model as well. This family could be replaced with just a box with some connectors. But we are using these 3D views to also generate our details by connecting to the system equipment and using the subscription Freeze Tool, and create a drafting view. Then we add text and annotation to it, and put the drafting view in our Revit Details project, which is a project file that only contains all of our drafting view details that can be inserted into our main Revit MEP projects.
Download Compressed Air Dryer
by Scott Brisk
Engineering BIM Solutions
Subscribe