Reference Plane w/ Negative Dimension Reference

[smbrennan]

I am working on creating a simple Panelboard for my company's use. I am starting with my reference planes and ensuring I can "stretch the model." I don't even have any geometry placed yet, and I'm stuck.  Here's my problem:

I have a Yes/No parameter, "Recessed," controlling whether the panel is Recessed or Surface Mounted. That is driving the "Mounting" parameter that's populated in panel schedules. I also have a "Wall Offset" parameter. This is for when the panels are mounted on Unistrut. Users can specify (per instance) 7/8", 1-5/8, 3-1/4", etc. Next, I have a "Panel Offset" parameter. This is using the formula if(Recessed,-Panel Depth, Wall Offset). My intent, is based off of the Front/Back Reference Plane, to place the rear of the panel relative to either the Wall Offset, or Panel Depth. But, if it's recessed, it needs to move in the opposite direction (into the wall). I think the negative value is the culprit, but I don't know the solution.

Does anyone have any insight? I've attached the family for reference.

Thanks.

[smbrennan]

Using the method demonstrated here:
https://www.youtube.com/watch?v=j3DlVzkNBRs

I am able to successfully apply a negative offset, but as soon as I associate it with a parameter, I am getting the same error.

[CoreyDaun · Accepted solution]

What I've done is to create a Reference Plane that is dedicated to hosting the panel's geometry and another that controls the recessed depth. The recessed Reference Plane is placed behind the Origin Reference Plane, and a dimensional constraint is applied with the formula below:

= if(and(Wall Offset = 0', Recessed), Panel Depth, 0')

The host plane is placed in front of the Origin Reference Plane and that Plane is constrained by another linear dimension back to the recessed Reference Plane. This will control the offset from the wall, and will be controlled by the user inputted value of "Wall Offset".

Attached is a modified version of your Family, in which I have horizontally staggered the Reference Planes so it's easier to see what's going on. I've also attached a version of one of my current Panel Family in case it's of any help. Note that if I intend to host my Panel to standing unistrut, I will create a Reference Plane or place a unistrut Family into the Project and host the Panel directly to that.

[smbrennan]

That worked! Thanks. I like your family too - gave me some ideas (something as simple as the Panel Name with Model Text). And that's quite the insane formula for your Automatic Feeder Size! Now I really feel behind on my Revit Knowledge. 

Could you please explain why the negative parameter doesn't work?

[CoreyDaun]

Yeah, that formula is crazy. That's because Revit's formulaic capabilities are so primitive. For instance, one cannot even CONCATENATE or combine text strings. I made an excel spreadsheet that compiles the extensive formulas for pasting into Revit. My longest formula can be seen in >THIS< thread.

Anyway, the reason that you cannot use a negative is that Revit cannot apply negative value to a dimension; they are one-way elements. It would make sense, logically, that the dimension would invert if a negative value was entered, but Revit is not built that way. There really isn't any more that I could explain beyond that.

[smbrennan]

Ok, I finalized my Panel family, at least for now (going to admit, I used a lot of ideas from yours, but not all), and when I inserted this into a project, the back face was on the exterior surface of the wall. I'm pretty sure this has to do with the fact that (I believe) I started with a Generic Model, and not a face based model. 

Is there a way to change this? I followed your post here, but because of the "Generic" type, I don't think it worked.

Thanks.

Edited by
Discussion_Admin

[CoreyDaun]

Dang... I should have noticed that when I saw your Family, my apologies. Yes, starting a Family with the template "Generic Model" versus "Generic Model face based" makes a big difference. Using the "face based" version enables you to use the "Place on Vertical Face" option when placing the element in the Project (see image below). My panel families are all intended to be mounted to a vertical surface, so they are "face-based". My transformers (most of them) are pad mounted, so for those I used the "Generic Model" template.

Unfortunately, there is no way to convert your Family to a Face Hosed family. The thread that you reference refers to Family that are hosted specifically to "Walls", "Ceilings", and "Floors" in lieu of a general plane. This causes problems because Revit does not recognize "Walls" that reside in a linked model as "Walls", so the "Wall-Hosted" Families cannot find a valid host.

BTW - your link reference "Page 2" of that thread; whenever possible, either provide a link to the thread in general or to a specific post (click on the post's message number). The reason why I say this is because some users (like myself) show many more posts per page (under My Settings) so there is actually no "Page 2" to that thread to me, so the link doesn't work as intended.

[smbrennan]

No worries. It took me no time at all to recreate the family. Actually, it helped me understand exactly what you were doing with the host reference plane - it forced me to disect the families you uploaded to understand how you were achieving the results.