by Dennis Collin
Revit MEP has had some electrical containment tools for the past ten or so years. This includes Conduits and Cable Trays, along with fitting components for these element types. However, Cable Trays do have certain limitations in that the channel shape can only be set to a horizontal aspect where the bottom edge runs parallel to its supports.
In many applications particularly in the infrastructure space, there is a need to be able to rotate the ‘C’ channel section so that the bottom edge follows a wall or trench which is typically vertical.
Fig 1. It is not possible to rotate cable tray about its cross-section axis, but with beams you can.
Whilst this can be achieved with structural beam elements, this cannot be achieved with the out of the box cable tray families. Structural beam elements possess a cross-sectional angle parameter which rotates the beam along its longitudinal axis. Whilst this creates compelling geometry the beam’s behaviour, category and classification settings to do not relate to Electrical Engineering. A better approach therefore is to create a face-based family, classified as a suitable electrical category. In this example Electrical Equipment is used.
Fig 2. This principle can also be applied to Cable Trunking and Ductwork as well!
A face-based family will host onto any surface and will enable the cable tray to follow a wall length or follow its height direction with the simple pressing of the space bar key.
Fig 3. Classified as Electrical Equipment will mean geometry will be easily visible in Electrical Discipline Views.
In a plan view, some reference planes are set out to define the length axis of the custom cable tray. Some additional locked dimensions are added to the end reference planes to accommodate some void cuts which will enable the cable tray’s corners.
Fig 4. Extrusion Profile Sketch (in left elevation view)
If the length and width of the tray needs to be scheduled or tagged. The parameters need to be set as shared parameters.
In the left section view additional reference planes are constructed and assigned a width parameter. Once the framework is completed, extrusion is created with the linework, and geometry locked onto the defined reference plane framework. The result of which should look like the geometry in fig 3.
Fig 5. Modelling an extrusion to form the rotated tray (or trunking) element.
To form corners void extrusions are sketched, snapping onto the offset Reference planes at the beginning and end of the extrusion.
Fig 6. Linking Void geometry to a cut/uncut parameter.
To control whether a corner cut is applied, a yes/no parameter is added and linked to each cutting void element. In this example 6 voids are created to cater for the various permutations of corners required. In this example, Vertical Corner, Internal Corner and External Corner at the start and end of the extrusion. Since each tray is likely to be unique these are set as instance parameters to be enabled as required.
Fig 7. Making use of the Cut parameter & Voids to control the application of corner geometry!
Once loaded into a project the face base element will host onto any surface or nominated work plane, this can be in a 2D, or 3D view, but for the control of junctions and mirror and copy operations and for easier alignment operations, a 2D plan, section or elevation view type is recommended.
Fig 8. Adding a piece of containment.
By default, a straight unchamfered piece of tray or trunking is created but by adjusting the parameters within the properties palette simple joins can be accommodated.
Fig 9. Adding Tray/Trunking to walls along with cabling.
For complex T Junctions or Reducers, Face based fittings could be made. Whilst not quite as neat or efficient workflow as the conventional tray or duct system families, they do not occur quite as often. Revit lacks the capability of creating cables out of the box. For 2D representation of cables, detail lines may be sufficient. However, for 3D and Perspective views I have found that Conduits can provide a satisfactory workaround. I will document that process as a separate blog.
Fig 10. Use conduits as cable routes for scheduling and visualisation purposes!
If Revit parameters are of interest, I have written a 4-part series of posts providing an overview of the topic.
Part 1, Part 2, Part 3, Part 4
Fig 11. With the correct parameter types applied custom schedules can be added.
Creating families, parameters and work-around solutions are some of the topics covered on our follow-on Revit content training courses. Visit the Arkance UK site to get an overview of the courses on offer and talk to one of the team for dates and availability or if you have more bespoke requirements, just ask, we are here to help!
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