Is this acceptable. The directions (sometimes found near the unit) where not available…
anyone?
Found instructions for mounting a Honeywell TZ-4 (looks as similar as I can find) that say
“mount only on a wall or cold air return”
I’m self actualizing! 
I usually find them just laying on top of the AHU. I don’t have the exact wording here in front of me but when I read an installation manual it said to adequately secure the controller in a safe location or something to that effect. I write them up and recommend the controller be more securely installed.
Mike,
I’d be writing it up. I’m sure it says somewhere in the installation instructions that the panel should be mounted on solid mount, free of vibration and adverse temperatures, etc. I know it’s made up primarily of PC boards, but vibrations can mess those units up over time.