Originally Posted by
HVACRsaurus
You are correct, too thin will not provide sufficient thermal mass
Too thick is a matter of reduced efficiency - as the ice becomes thicker the growth slows down, partly due to the increased volume, but also because ice is an insulator (the "cold" energy of the refrigerant is not transferred readily through thick ice)
Further, it is important that the ice serpentine does not build to such that the runs join together and form great big block - a block of ice may have more volume but it does have less surface area than distinct "tubes"
The systems I have worked on, between one and two "Diameters" of the copper tube is the ice thickness they use
Probably a bit of trial & error, hopefully you get lucky first time!