In article ,
Bob G. wrote:

I use a piece of plywood cut 1" larger all around than the
unit and hold it in place with something heavy.....like a rock
or a concrete block.

Only attempting to keep out leaves and allow air to circulate..
Both my sons are in the heating and a/c business they both
told me that 99 percent of the units they see with rust problems are
the ones whixch are covered ...

That cinches it: I'm not going to cover my new unit, either.

I am replacing a 1991 WattGobblertm condensing unit that has NEVER been
covered - and it has never missed a beat OR rusted.

Convince me that there exists a viable and CONVENIENT way to keep out
cottonwood tree "cotton" and I'll consider it.
--

JR