I have looked in the literature and do not see any reason not to mount a Controllogix Rack with Power Supply, PLC and I/O modules vertically. Reason I ask is we had a panel built outside the shop and they basically rotated the entire panel 90 degrees so that the top (PLC mounted horizontally the normal way) is now on the left side. We will rebuild it eventually but for debug is it OK to mount it like this temporarally??

I would think this would be an extremely bad idea. Horizontal mounting will be critical for heat dissipation. I think you are asking for nothing but trouble down the road by allowing the modules to overheat.

While it doesn't explicitly say that you must mount them horizontally, all the installation guidelines show a horizontal mounting. See page 8
http://literature.rockwellautomation.com/i...in080_-en-p.pdf

ControlLogix can't handle vertical mounting as it needs heat dissipation.
Only Flex I/O is approved for vertical mounting.
See TN 34499 for details

How about CompactLogix??

Only Flex I/O.