Temporarily suspending any thoughts about the actual words of the code (and please let's set Charlie's Rule aside for a moment), let's talk about the intent of the "dedicated space" rule. I think it is in place so as to allow the installation of conduits in the future. Dennis said the same thing in post #2. That is why, in my opinion, the rule only applies to panelboards, switchboards, and motor control centers. We don't have to maintain dedicated space directly above a transformer, a disconnect switch, or a VFD, specifically because once it is installed there will be no need to install additional conduits in the future. That brings me to the recessed panelboard. I submit that once it is installed, you are not going to be installing any more conduits. Many of my clients will require that I include in the design the installation of empty conduits that stub up above the suspended ceiling, so as to allow for future circuits to be installed. So I don't see a problem with recessed panels.
Now back to reality. Do the words of the code essentially prohibit recessed panels on the basis that they don't have dedicated space above and below them? I think not. I think that rule would prohibit running a pipe in the recess space above a recessed panel, but it would not prohibit having insulating materials above or below the panel. And if we are talking about the header being at the top of the wall, where it meets the ceiling structure, I would say that you just reached the structural ceiling.
