Originally Posted by Painted Skies
Ours appears to be primarily the result of the Corian countertops (which has to be one of the stupidest materials ever used on boats
This is a high possibility depending on what your countertop is. If wood, then not so much, but something like Corian will gradually get cooler and hold that temperature. It doesn't take much in a humid environment
to get condensation then.
We have Corian tops also, as well as 6" urethane foam beneath it. Our box is very efficient and we have no issues with freezing/cooling or excessive power usage.
However, when it is humid, we get a small amount of condensation on the top, and the Corian in this area is noticeably cooler.
The "problem" stems from the lid seals
. While they are tight and good, the rubber gaskets are not highly efficient insulation (or we all would just insulate our entire boxes with 3/8" rubber foam). This means the edges of the lid are always a very slight amount cooler than the center of the lid.
With a hard surface like Corian, this sets up the thermal mass problem where the coolness is retained in the surface rather than quickly equalizing with the air temp - and condensation occurs.
If your tops are wooden or similar, you should not have this situation (outside of unusually damp conditions where condensation is immediate on everything).
However, it if is hot and raining in Miami
like another poster said, then I'm surprised your reefer top is the only thing on the boat covered in condensation.