I own a condo in Chicago that has individual room units...PTAC...they are all older units and am looking to replace a couple. The problem is, they are inside mounted units. Nothing shows at all on the outside of the building. Im am sure that the association will require the same type unit as a replacement. Do they have such a thing that is installed only from the inside of the home?
A PTAC always has an exterior grille of some sort- there's no such thing as an air source heat pump that doesn't have access to the outdoor air! A PTAC just has the interior and exterior parts contained in a single module, making it more like a window air-conditioner than a split-system like a mini-split or ducted air conditioner with an air handler.
You need to figure out how big the opening for the PTAC is in order to find one that actually fits, and whether the exterior side view will change with a new PTAC. Often they are screened from exterior view by architectural elements, or a grille affixed to the building, behind which you can install something of smaller or equal dimensions.
On the up-side, there are now PTAC units with variable speed scroll compressors & variable speed blowers, which are whisper-quiet and efficient compared to old-skool versions. It's usually worth the upcharge for going with a better, quieter unit rather than replacing it with a legal-minimum efficiency version.
BTW: Are these AC-only, or PTHP heat pumps that do both heating & cooling?