Ducts, Fittings, and Model Groups.

[identity4]

I have been working on a large Dorm project and have been having some trouble working with model groups for my HVAC equipment and ductwork.

Problem description: I join two ducts together inside of a model group, duct takeoff (tap) fitting becomes excluded from the model groups. I place a duct cap at the end of a duct, cap and/or duct becomes excluded from the model groups.

Question 1: Why does this only seem to occur with duct fittings?

Question 2: What are the implications of having a model filled with model groups and tons of excluded duct fittings?

Question 3: What is a “Center Line” and why is it breaking things?

Possible options available with my limited Revit knowledge:
1). Ignore problem, enjoy excluded fittings. (Unknown implications down the road)
2). Break model groups, make all future duct changes without them from now on. (Time consuming)
3). Ungroup, make changes, regroup, copy new group around the project, redo all tags and annotations on my sheets. (Time Consuming)

[drewj]

Because you haven't had any other reply's I will let you know what I found (unfortunately nothing like a solution).

I created a run of 450mm round duct and put a round 250mm branch into it with a Tap connection, then made a group of this. I copied this group and then proceeded to modify the group by putting another 250mm branch into the 450mm main and added a cap to one end of the 450mm main. At no point did I get any sort of error. i am running Build 20150303_0715(x64) UR7.

If you have an example file I would be happy to take a look at it where I would be able to replicate the error.