Friday, December 15, 2017

Revit Alternates; Phasing vs. Design Options

When working on a multi-disciplinary project, what is the best way to deal with bid alternates? The biggest challenge relates to MEP systems in Revit. These systems allow us to properly calculate loads, such as electrical and CFM.

In this post I do a mockup of Design Options versus Phasing… neither are perfect.

Design Options:
The first image is the base bid plan view. The East wall and two receptacles are in the ‘base bid’ deign option (which is primary). Those two receptacles are properly connected to the panel which is not in a...
design option (main model). Thus the panel properly reports the total load for the main model and base bid (just like a normal set of drawings).

This next image shows the alternate option turned on, thus base bid off. The two receptacles are now hidden, along with the east exterior wall, but they are still connected to the panel. For the alternate, there are three added walls, four receptacles and a panel in the secondary design option. Devices in a secondary design option cannot be connected to anything outside of that option (unlike the primary option). However, the four receptacles can be, and are, connected to the panel in the secondary option.
One way to segregate the base bid load is to add a sub-panel to the base bid design option. This option is shown in the first image, on the south end of the east wall.

This model has been created to match the Design Option example above. The east wall has Phase Demolished set to Alternate. The electrical panel and devices cannot have Phase Demolished set to anything otherwise it will globally disconnect from the main panel.

In the Alternate view shown below, the exterior wall is automatically removed (based on the Phase Filter settings for the view). However, the electrical panel and devices still appear… one option would be to select them and hide by element. But this would need to be done in every view, and every time new devices are added.

Back to the Design Options workflow for a moment... the last three images show steps required to set up the views for proper display. This is for an MEP model with a linked architectural model.

First, create the design options in your MEP model.

Duplicate the plan views, and name accordingly for required alternates. Set the view to show the desired design option as shown in the image below.

You also need to set the link to show the same design option (this is a design option created in the arch model, best if they all are named the same).

And back to Phasing for a moment as well... here is the warning generated when you try to demolish a connected device in Revit.

As I mentioned at the start, neither option is perfect. However, unless there is a compelling reason, I prefer to stick with the Revit workflow most closely designed for the task. In this case, that is Design Options, as this extra building is not a future phase. If it were a future phase we would not be having this discussion:)

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