Revit Family Tricks for Electrical Content ® Family Tricks for Electrical Content 2 Revit...

About the Speaker: Robert is the Design Technology Manager for Sparling, the largest specialty electrical engineering and technology consulting firm in the United States, headquartered in Seattle, Washington. He provides strategic direction, technical oversight, and high-level support for the Sparling enterprise design and production technology systems. He is instrumental in positioning Sparling as an industry and client leader in leveraging technology in virtual building and design. Robert has been writing code for customizing AutoCAD® since the release of AutoCAD v2.5. [email protected]

Revit® Family Tricks for Electrical ContentR. Robert Bell – Sparling

ME30-1R Let's face it, electrical content for Revit is not the sexiest discipline when it comes to 3D

models. Usually boxes and other blobby models are enough for the electrical engineer. Revit doesn't deal

with annotation symbols quite as seamlessly as one might hope. And yet there are tricks that you can use

to do some amazing things with symbols that you just can't do in AutoCAD. However, there are also some

"gotchas" with content of which you need to be aware. This class will discuss tricks that you might find

useful for your own content.

Revit® Family Tricks for Electrical Content

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Revit electrical content offers features not available to AutoCAD MEP content. This class will

discuss some of the ways in which Revit provides flexibility that is either difficult or impossible to

provide in AutoCAD MEP.

The following topics will be discussed:

! Light switch banks

! Plan symbols can be moved independently of the actual model

o Off the wall

o Along the wall

! Changing plan symbols by changing the family type

! Light fixtures that can show both an emergency fill and provide for a tag where needed

! What’s wrong with “always vertical”?

Light Switch Banks

Light switch banks are a bit of a pain, depending on how far into the BIM you get. If all you need

are plan symbols on sheets then life is easy. It gets much worse when you need to provide a

model of something more than a single-gang box where connectors are involved. There are two

difficulties. The first task, making a family with can model a variety of switch banks in one family,

is the easier one. The second task is far worse. Although you can put multiple connectors in the

family, the current architecture of Revit MEP does not permit multiple switch systems on a

single element. Therefore, from a BIM perspective, we are “stuck” with two family types: one to

show the switch bank and another to provide the switch systems.

As with most things Revit, there are multiple approaches to issues. The following is not

promoting itself as the best solution. Indeed, it has its own issues. However, it is an attempt to

provide solutions to the two issues noted above.

Deciding how to deal with the first issue really depends on the approach taken to deal with the

more important second issue. If you need your BIM to be accurate enough so that the selected

switch has the correct switching system than you are left with the requirement for a switch family

to have a single switch connector. Ok, so one connector equals one switch. Each plan symbol

switch will have a connector since there is no reason to place a switch symbol without

connecting that switch to a switch system. Therefore, it becomes obvious that the family will

need the ability to turn off the 3D model for switches that are placed in support of the switch

systems and are not representing the actual switch bank.


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Figure 1 Switch Banks in Plan and Elevation

This makes things easier from the perspective of family editing. We don’t need to deal with

attempting to array plan symbols and connectors. We will need to indicate to the designer that

the switches are placed without an accompanying 3D model. This can be accomplished in

several different ways. One is to use a filter to change the color of switches that do not have a

3D model. Another approach is to use invisible lines to indicate the state of the 3D model when

the switch is selected. The filter approach has the advantage of being immediately obvious. This

is the approach I prefer to give to the designers.

Figure 2 Filters for Switch Banks

Create the required elements in the light switch family to support the model of the switch bank.


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Figure 3 Model Elements

Create type-based Yes/No parameters to control the visibility of each of the switches in the

switch bank. The family created for this class only supports a switch bank of up to four switches

so there are four Yes/No parameters for each of the four switches.

Figure 4 Light Switch Model Parameters

The visibility parameter for the elements for each switch is set to the Yes/No parameter for that

switch. The faceplate and backbox elements’ visibility parameter is set to the “1 Switch” Yes/No

parameter because there is no need to show those elements unless at least one switch is

visible.


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Figure 5 Linking Switch Visibility to Parameter

Plan Symbol Offset off the Wall

When you select the “Maintain Annotation Orientation” parameter in an electrical fixture family

this forces the nested annotation family to be “glued” to the vertical face regardless of where the

nested annotation family is moved within the host family.

Figure 6 Model Family Using Maintain Annotation Orientation


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But there is a way around that behavior. Offsetting plan symbols require the use of a nested

annotation family. The annotation family can be designed so that its graphics are moved by

altering a parameter.

Figure 7 Annotation Family Parameter to Move Elements

This is easily done with the use of a group. (There is another approach of using yet another

nested family however, this is needlessly complex.)

Figure 8 Annotation Family Elements Grouped


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The model family has a parameter that is linked to a linear dimension that moves a weak

reference plane drawn in the front elevation view. The linear dimension needs to be

dimensioned from reference plane to reference plane and not the reference level. The weak

reference plane provides a grip on the placed element to move the plan symbol off the wall.

Figure 9 Weak Reference Plane for Grip to Move Symbol

The nested annotation family’s parameter for moving the group is linked to a parameter in the

model family.

Figure 10 Linking Model Family Parameter to Nested Annotation Family Parameter


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There is a complication. The length to move the nested annotation family is based on annotation

scale. For example, if the element is placed in a view with a scale of 1/8”=1’-0” then the

measured distance you would expect to move a symbol might be 12” but the required length to

move the nested annotation family is only 1/8”.

The only approach I have currently found is to use another parameter than you can change for

the primary scale of the model. This parameter is set to 96 because the majority of our plan

views are 1/8”=1’-0”. A project where the majority of plan views are 1/4"=1’-0” would have the

parameter set to 48 to improve the relationship between the grip distance and the plan symbol

offset.

Figure 11 Parameters to Adjust Grip/Symbol Movement

A filter can be created to change the visibility of symbols that are offset. This is needed in order

to QC plans.

Figure 12 Plan Symbol Offset with Model in Correct Location


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Plan Symbol Offset along the Wall

Offsets along the wall are much easier to accomplish. All that’s required is to move the nested

annotation along the plane of the wall. There is a complication. To provide a grip for moving the

plan symbol a dimension driven by a parameter is required. Yet negative linear dimensions are

not permitted.

The solution is to create a fixed plane well to one side of the Center (Left/Right) plane. This

fixed plane will permit a dimension with a parameter to be placed and provide the ability to move

the plan symbol at least to that fixed plane and no farther. This is actually desirable rather than

providing unlimited movement of the plan symbol. This will reduce the chance that a plan

symbol is located at an extreme distance from its model.

Figure 13 Fixed Plane to Avoid a Negative Linear Dimension

Two planes are used to control the movement of the plan symbol using the fixed plane as the

anchor. One plane is set to a weak reference to provide a grip for moving the plan symbol.


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Figure 14 Weak Reference Plan to Provide Grip

The other plane is not set as a reference and is used to actually move the plan symbol and limit

the movement away from the fixed plane. A reporting parameter is used to report the distance of

the plan symbol to the left or right of the Center (Left/Right) plane.

Figure 15 Plane to Move Nested Annotation Family

Providing the limited range of movement on the opposite side can be accomplished by the use

of a formula. However, the grip can still be extended beyond the plan symbol limited range. This

is not desirable but the grip is usually not moved a long distance from the plan symbol. The grip

can be reset by using the procedure below.


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Figure 16 Parameters to Limit Symbol Movement and Report True Offset

Resetting the plan symbol back to the model location is done by changing the “Grip Along Wall”

parameter to the length required to synchronize the plan symbol to the model. In the case of the

sample family shown in this class, that length is 4’. Of course, this distance might be confusing

to the designers so a reporting parameter is used to show the true offset. When it reads 0’-0”

the plan symbol is synchronized with the model.

A filter can be created to change the visibility of symbols that are offset. This is needed in order

to QC plans.


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Figure 17 Plan Symbol Offset with Model in Correct Location

Family Type Parameter

Certain families lend themselves to having multiple plan symbols since the model itself does not

change much, if at all. One example would be a single and duplex receptacle. The backbox and

faceplate are the same between both (even if you get detailed with the faceplate at the fine

detail level, the overall dimensions are the same) and the load can be varied by changing the

family type. The plan symbol is obviously different.

If the choice is made to create one family to support both receptacles the visibility of the plan

graphics needs to be controlled. Since the term “visibility” immediately comes to mind, the

tendency is to use the Visible property of the element to control the nested annotation families.

The issue is that that property is a Yes/No parameter. This means that Yes/No family

parameters are needed to control the linked element property. This can lead to a family with a

series of Yes/No parameters to show only the correct plan symbol. There is a better way to

handle this.


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You need a separate annotation family for each plan symbol. Load the nested families in the

host family. Select one of the nested families and place an instance. There is no need to place

instances of the other families. A single nested family element is all that’s required. Create a

new family parameter (type or instance based as needed) and select the “<Family Type…>”

option for the Type of Parameter entry. Select Generic Annotations from the Select Category

dialog box.

Figure 18 <Family Type…> Parameter

The parameter will display all the loaded generic annotation families. Create family types as

needed to accommodate the different plan symbols.

The final step is to select the plan symbol element and change its Label property to match the

parameter name you created for the host family.


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Figure 19 Populated Parameter

Each family type will use the nested annotation family as specified in the “<Family Type…>”

parameter.

Figure 20 Multiple Plan Symbols in a Single Family

Life Safety/Critical Fill Patterns and Tag Support

Revit suffers an issue with sloped surfaces. It will not display an associated nested annotation

family unless the host family was created as a non-hosted family with the “Always Vertical”


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parameter checked. This is not a realistic model since the 3D model will be tilted out of plane of

the surface to which it is hosted.

The “always vertical” approach may be required for families that need to display a nested

annotation family but is not the only approach for larger elements such as light fixtures. You

may decide that you want to use face-based families for light fixtures.

Many engineering firms and the National CAD Standard use fill patterns to indicate lighting

fixtures on life safety or critical circuits. Recognizing the current limitations with the Revit display

engine, it would be a good idea to at least provide an option to tag a fixture on a sloped surface

as being on one of those circuits in addition to the fill pattern on a level surface.

Create two Shared Type parameters, Yes/No; one for indicating the family type is on a life

safety circuit and the other for critical circuits. Name the parameters “Is Life Safety” and “Is

Critical”.

Create a normal Type parameter, Yes/No, to control the visibility of the fill pattern. Name the

parameter “Show Fill Pattern” with this formula: or(Is Critical, Is Life Safety)

Create a Shared Type parameter, Text, to provide the text for the tag. Name the parameter

“Circuit Type”. Add it to the family as a Type parameter. Use the following formula: if(Is Critical, "X", if(Is Life Safety, "Y", " "))

Figure 21 Parameters to Support Both Fill Pattern and Tag

Doing this provides a family that can show both a fill pattern on horizontal faces and provide for

a tag when the element is on a slope face.


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Figure 22 Fixtures in left Room on Sloped Ceiling at Least Have a Tag

Is “Always Vertical” the Solution?

Granted, the same fixture type on a life safety circuit showing with a fill on normal ceilings and

needing a tag on sloped ceilings is not ideal. As engineers, getting sets approved by an Agency

Having Jurisdiction (AHJ) is a primary concern. Many AHJs are accustomed to seeing fill

patterns for fixtures on a life safety/crucial circuit. However, the industry is rapidly embracing

BIM and modeling can have odd repercussions in the AEC industry. Users of Revit need to deal

with model issues for which the AHJ may care less.

The “Always Vertical” parameter is an attempt to address a current limitation to the Revit

engine. Elements on a sloped face in a plan view do not display their plan representation even

though Revit “knows” the view is a plan or RCP view.

However, this parameter is not useful for elements place on a sloped ceiling. The perfect

example is an array of 2×4 light fixtures on a sloped ceiling in section. Notice Figure 23. The

plan representation is what the AHJ would expect. However, examine the effect in the section.

Can you imagine what the architect will say when they link the electrical model and want to

render that room for the client? An even more significant issue is that the clash detection is

invalidated with such a model.


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Figure 23 Correct Modeling Sacrificed for the Sake of Plan Representation

The current solutions are far from ideal. Should you choose to create a plan that the AHJ easily

understands, the architect will be unhappy with your model. If you choose to model more closely

to reality, the plan may have a mix of element representations that require additional annotation

to clarify the intent of the design.

Conclusion

Revit families provide some interesting options for the electrical modeler. There are features in

Revit that cannot be duplicated by content in AutoCAD. The release of Revit MEP 2011 was a

milestone release for electrical design firms. There is little reason to avoid performing electrical

design in Revit when using Revit MEP 2011. Experience the exciting options available to the

electrical Revit designer for yourself.

Revit Family Tricks for Electrical Content ® Family Tricks for Electrical Content 2 Revit...

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