Fan coil units fall under 23-33 33 00 in the 2012 standard.

Ah - I see - the reference Im looking at must be a newer standard then

In case anyone stumbles across this thread - heres the link to the OmniClass 2012 text file that Autodesk links to.
Chris: Note that the syntax is different than the one you attached above.

Sorry, I revised mine to remove the periods to match the standard, I don't know why the periods exist... sorry, I did know at one point at the link here

Unfortunately the link in the post, to the answer, doesn't work anymore

Can't be a newer standard, 2012 is the National standard for Table 23-Products (according to Omniclass.org)and hasn't been updated since then, so I don't know where you were got those numbers from.

I think this link started my rabbit hole search.
In 5 years when this comes up again, the periods were added because it was based off an old draft version of the standard.

I believe I have found a complete solution to the incorrect OmniClass Taxonomy file that still ships with Revit. The process described by Autodesk here:

does in fact work, however, the OmniClass 2012 txt file that you acquire from the download link they provide has several flaws:
1) The numbering system is not the same as the actual OmniClass standard (uses periods instead of spaces, as others have pointed out)
2) The parameters for category sorting are missing
3) The text is not uppercase (perhaps this is just my personal preference, since I like to have all text in my construction documents to be all caps, which is also a general NCS standard)

After digging through the Autodesk Classification Manager and some tinkering, I was able to solve all three of these problems and get it to work properly in Revit. Please feel free to download and use this file, I hope it helps resolve this baffling problem that Autodesk should have fixed 5 years ago.

I purposely left the categories out of my file because I'm *not* going to let Revit dictate how I'm going to classify an element. Might be a bit more time to find what you need but you have complete flexibility to assign any classification # to any element.

I hear you, nobody likes a dictator, but the category sorting parameters do not actually dictate anything. They are there purely to help speed up the process of finding the most relevant classification as quickly as possible by reducing the amount of information you have to sort through at once. You still have compete freedom to look for and assign classifications from other categories or even all categories; all you have to do is switch up the category filter from the "Show classifications for:" drop-down.