Thanks for your replay...
Yes, is that what I am looking for and I know that is not a easy and clear solution but I am sure is possible to combine a few "new" parameters, add a formula and get the precious solution!
How did you try to find a solution? What have you done?
Maybe together we can achieve what both need!
Unfortunately I think too many variables would need to be overcome to achive this through formula's only. I certainly don't mean to discourage, but I think the only way to achieve this would be through the API. Here is why I think this.
1. If we had a "Type of Parameter" that allowed us the ability of sequential designations similar to what "Mark" Provides we could accomplish what we are looking for by creating a label with 2 parameters "Equipment Type + Equipment Designation". Unfortunately this ability has not been written in.
2. I have attempted to isolate AHU's, VAV's, FCU's by using an "Equipment Type" Parameter which is easily achieved, however the "Mark" parameter is a hard coded parameter which will not allow us to populate formula capabilities. This stops us from using the "Equipment Type" parameter and "Mark" Together to achieve this. In addition this is not a viable option as I think I mentioned before it would most likely result in "Duplicate Mark Value" errors which creates more to clean up in the model.
3. Even if we knew of a formula function that would allow a number to be sequentially added to the previous number after finding the "Equipment Type" we would need the parameter to be a project parameter to be able to get it to work. This is the only way I could see us being able to pass a "+1" formula to an existing number each time a piece of Mechanical equipment is placed.
Unfortunately project parameters do not allow formulas which stops us again dead in our tracks.
With all of the walls I keep hitting the only way I can see this being achieved without Autodesk providing us these features in the platform is through the API which I am not yet fluid enough in writing C# code.
Again I do not mean to discourage, I am open to ideas and solutions to solve this problem but I am running out of options.
I add a new and first FCU from the project where the ID/reference from the new parameter that we create is 001, the second to be 002 - we could just simple create a text parameter, where we could just type the new reference or we could create something "smart" that will recognise the previous FCU as 001 and will automatically give 002 to the second, 003 to the third and so on...
Are you going to use this automatic parameter that has 001, 002, 003... in your drawings/schedules or is it something for internal use only? If the latter, you can skip the following rant and i misunderstood you completely.
Before I take a stab at how you're going to try to achieve this (most likely through programming), you should ask yourself what is the benefits of this and the drawbacks of this. You're trying to get REVIT to automate an easy yet important task as designating equipment! What if you don't like the number that REVIT gives your AHU? What if someone else created a bunch of AHUs and wanted to number them differently but couldn't because that designation is solely dictated by REVIT and your formula or the order in which they were created? What if you wanted to use text in your designations ... are you going to mess around the ASCII code to try to get the next AHU in sequence after 1A to be 1B or 2A? Lets say someone accidently deletes an AHU, the other AHUs get moved down a spot (like you want them to?), then tries to undo but REVIT can't get the previous number back so that deleted/recovered AHU will get the next number in line? How about multiple people working on a large project ... they're trying to create a bunch of VAV boxes but they keep getting designations that are far apart because other people are also trying to create VAV boxes. Would that not annoy them if they already know which designations they want to use and not let REVIT and your formula decide what's best for them? Don't get me started on copy/pasted items that are moved around, deleted, put on another design option that's to be either forgotten or deleted later on! What about multiple files with multiple VAV boxes ... how will REVIT know what number to go to for the next VAV box? What if you wanted to renumber all your VAV boxes because something occurs late in the project that is unforseen?
You ever wonder why the mark (or type mark) parameter acts the way it does? Some smart programmer decided that it's cool that "mark" should be unique and warn the user that there's a duplicate of "mark" (because AHU-1 and VAV-1 can't happen, clearly the stupid user's fault for attempting it ... i just use my shared parameters and skip mr. smart programmer's warnings)! Then he decided to write some code to get the next mark for a new element should be set to some next in line number or text so that you don't get a warning every time you create something (but when you change the mark, you'll most likely get that warning).
All very valid points to consider on why to use or not to use such a feature in certain circumstances. Which I agree some of the points you make build a strong argument on why not to use such a feature in the situation of AHU-1, AHU-2. However knowing how to accomplish this method could apply it to a large number of situations that could benefit and have a strong argument on why you would want to use such a method. I would like to think of the application in which we are discussing to apply a possible method is only a vehicle for it's potential use.
Another example of where this could be applied is if you wanted to tag the number of FCU's or VAV's on a floor plan so that you can look at the highest number on the plan to verify counts. Most likely an internal use only.
Ex. Level 1 - 1st Instance = 1.1
Level 2 - 5th Instance = 2.5
Another possibility is an order of installation schedule (going way off topic here) where the sequential number assigned to FCU's or VAV's could be scheduled and assigned as the primary "Sorting/Grouping" parameter which will build a step by step schedule of installation based on the order they were placed.
These are only a few examples but my point is that each of us would be able to find a useful application for it's method depending on how each of our firms work.