Aside from access,clearance and height, what issues might come into play (aside from internal contact damage) with mounting a disconnect to the side of a transformer, a metal air duct, a condenser or other non-wall surfaces? Could you glue a disconnect to a glass surface? I see disconnects on AC condensers that would block the access for replacing the compressor motor. The inspectors never seem to mind. What do you think??

The last part of 440.14 is intended to prevent that.

"I see disconnects on AC condensers that would block the access for replacing the compressor motor. The inspectors never seem to mind. What do you think??"

I write red stickers for that! So does my other inspector. As Don said 404.14 is cited.

As to using glue on glass, I have never seen anyone attempt that type of installation.

I had to laugh at the glue idea.

A few years ago I had a major argument with an Interior Designer about the location of a wall phone on the plans. He INSISTED that it be mounted exactly where he showed it.

When I finally 'caved in' and quite arguing I told him that it would be right where he had shown it, but I pointed out to him that the conduit would be surface-mounted. This threw him into another tizzy which finally ended when I showed him on the overall floor plan that the 'wall' where he wanted it was a full height window to the outside.

He then angrily told me that I could put it anywhere I wanted...I stopped myself before I offered a location that would have gotten me in trouble with anyone possessing delicate ears.

LMAO...and thanks for the morning chuckle

"CALL AN ELECTRICIAN, WE HAVE A BROKEN WINDOW!!!" HAHAHA!
You know it's been done somewhere......

Been done somewhere? Did I hear someone mention my name?

We had a glass-enclosed architects' office, one that sat on the edge of an indoor pool. After our multiple RFI's were ignored, we mounted the thermostat to the glass with double-stick tape, and the t-stat wire just hanging in the air.

The install failed to be noticed through several inspections; only after 'final,' when the man's wife came to visit, was it noticed.

Yup, the 'award-winning architect' had so much glass that there wasn't a good place to mount the thermostat. Oops . Well, we eventually made a bracket for a door frame, and fished the wire through it.

Disconnect mounted with a double face tape is interesting.
I am sure the glass has to be tempered before you can safely mount anything on it, but will inspectors fail that installation?

I feel your pain,
Not so long ago, I wired/fitted one of these "architecturally designed" "buildings", more glass than walls.
Us contractors on site started calling it a fish-bowl.

Oddly enough it damned near turned into one as there was a hole in the roof where the un-supervised roofing labourer left out a bit of steel roofing profile and we had one of the biggest rain-storms of the winter season, overnight about 6 days from the end of the project.
Many cielings were wrecked and most had to be replaced as well as the few walls that did exist the plaster-board was ruined.