I did this install and was told not to put the wires up. This is an air conditioned space with no exposure to the elements. Makes a much cleaner install in my camper if they are wires up.
asked
MPPT install with wires up
Violates IP certification. Air contains moisture, even more relevant with an air conditioner. Do not mount it that way. Water doesn’t flow uphill for a reason.
Wiring for convenience only causes problems.
I flipped them. 
