Panel elevation above grade?

Anyone have a code reference on a minimum panel elevation above grade.

I ran into (2) Zinsco sub panels yesterday on a small duplex located approximately 12" above grade. Lots of rust/corrosion from roof run off over the years.

As far as I know there is no minimum height, just a maximum height.

the only minimum height on panel enclosures I am aware of pertains to mobile home panels located outside…which has a 24".

Thanks Guys!