Get a Grip!

December 8th, 2011

Electrical construction documents depend upon the use of symbolic representations for devices in plan view. The symbolic representation for a receptacle, for example is larger than the actual three-dimensional modeled receptacle used for elevations and interference detection. It has to be larger to effectively convey the receptacle type and still be readable at a 1/8th scale. Because it is oversized, however, placing receptacles close together in the model causes the plan symbols to overlap. That is, unless the symbolic part of the family can be independently moved from the modeled component. Using a receptacle family as an example, this article will demonstrate how to do just that.  

Begin by creating the symbolic annotation family of the plan symbol. Use the generic annotation family template provided with Revit.  Name it “Family_A.” Using detail lines, draw the plan symbol at the size it would be on a plotted sheet.  

Controlling Up and Down Movement

Create another generic family. Use the generic annotation family template again.  Name it “Family_AA.”  Load “Family_A”  into “Family_AA”  to create a nested family.  Place the nested symbology above the horizontal reference plane in Family_AA, but centered on the vertical plane. Draw a horizontal reference line under the symbology, and make it a weak reference.               

                                        

Using an aligned dimension or the Align tool, lock the nested receptacle family to the reference line.  Add a dimension from the reference line to the horizontal reference plane in “Family_AA.”  Add an instance parameter to the dimension and name it “Offset From Wall.” This will add the ability to move the plan symbol away from the hosting wall or entity.

Create a third family using the Generic Face Based or the Generic Model template. Wall-based or other options can be used here, so pick what works to maintain company standards.  In any case, the family will be built the same, but “push/pull” options are slightly different once the family is placed into the model. Name the new family “Receptacle.”

Create the following instance Parameters in the new family.

Offset From Wall <Dimension>
Offset From Wall2 <Dimension>
Offset L R <Dimension>

 

Create the following type Parameters in the new family.

Plan Symbol <Family Type>  <Generic Annotations>
Plan Scale <Length>

 

Load “Family _AA” into the “Receptacle” family and place it on the intersection of the two main reference planes.  Assign the “Offset From Wall” in your nested family to the “Offset From Wall2” parameter in the host family by selecting “Family_AA” and selecting the box to the right of the “Offset From Wall” parameter in the Properties palette and then selecting the “Offset From Wall2” parameter in the dialog that pops up. This will allow the user to add a dimension to move the receptacle symbology off the wall without moving the model portion of the family.

Because the receptacle family scale is based on the plan scale, and it is unknown what that scale will be until it is placed in a view, a way to push that information to the family is needed. Otherwise, an entered 6” offset may move the receptacle symbol radically more or less than 6” on the plan.  The Plan Scale parameter will be used as a mechanism for the user to convey the view scale to the family. At this time, Revit families do not have a parameter for the scale of the view in which they are placed. Click on the Family Types button on the ribbon and, as a default, set the “Plan Scale” parameter to 0’-0 1/8”.  To get the proper offset for any scale, add the following formula to the “Offset From Wall2” parameter “Offset From Wall / 1' * Plan Scale.” The “Plan Scale” parameter must be manually entered by the user.

Controlling Left and Right Movement

To control the side-to-side movement of the receptacle symbol, a vertical reference plane must be dimensioned and labeled. Revit will not allow negative values in dimensions, so the base plane can not be placed in the center of the symbol. To allow the offset to go both left and right of the center reference plane, add a reference plane to the 4’ left of the center reference plane.  This sets the maximum offset, so adjust if required.  Set the “L R” default to 4’, to align the plan symbol and the elevation symbol when families are placed.  

This plane should be pinned and set to “Not a Reference.”  Create another reference plane and name it “L R.” Lock “Family_AA” to this reference plane, and make it a weak reference.  Add a dimension from “L R” to the left reference plane, and set it to “Offset L R.”

Swapping out Symbology

Repeat the steps above to make different types of receptacle symbology (duplex, double duplex, emergency, and so on). Load the new symbol families into the receptacle family, but do not place them.

In the Family Types dialog, create multiple receptacle types. Associate the Receptacle Type parameter with the appropriate type loaded in the family.

This method helps when circuiting. Revit will trim the wiring to the extents of your family.  If the check box to control the visibility of symbols of different sizes is used, wires may be trimmed too short or too long without this method. 

If using a face-based family, the “push/pull” grips to control the left and right location of the symbolic annotation now exist, but the offset from the wall distance must be manually typed in the properties dialog.

If using a generic family, the push/pull grips exist for control left and right as well as the offset distance from the wall.  One benefit of using a generic family is that it does not require an architect model to host on.

Don’t forget to model the 3D portion to the family.  For brevity that has been left out here. Typically only the faceplate is required.

Move Around a Label

Another use of push/pull grips is for the ability to move labels that are part of a family.  In a 3-way light switch family for example, the label “3” comes in perpendicular to the wall the switch is placed on.  The “3” usually needs to be moved to avoid conflicts with other symbols.  Three options come to mind. 

Option #1:
Add a label as part of the family.  The problem is, that as part of the family, the label cannot be moved. 

Option #2: 
Tag the family.  The tag can be moved, but it can only be vertical or horizontal.  On an angled wall the “3” will not be perpendicular.

Option #3:
Use text.  Text will rotate to any angle, but it is not part of the family and won’t update. 

Push/pull grips can take Option #1 further. Just like the receptacle family example above, a label can be placed into a generic family and added to the switch family allowing the label to be moved left, right, and off the wall while staying perpendicular to an angled wall.



Most of the time, Option #2 is preferable, but using the Push/pull grips provides flexibility to handle any situation.

It has been said, “Revit cannot do that!” but with a little ingenuity, most any problem in Revit can be addressed. There are many more uses for push/pull grips, so don’t be afraid to experiment. Find out what they can do for you.

Mitchell Voss is an engineering technician for Alvine Engineering, Omaha Nebraska. Mitchell has been working with Revit since Revit MEP 2009, primarily on the electrical side. He has been a technician in Omaha since graduating from Southeast Community College in Milford in 2000.

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