Jack, I know I won’t Change your mind and I am sure you believe what you say but I would like to point out a few things regarding boat ice box conversion units. After building several hundred holding plates and working with at least 1000 boaters I did form some strong opinions about what works and what does not. The degree of refrigeration temperature acceptance varies from one boater to another. If you ask all boaters which refrigeration is best there will be someone who like every system sold.
The facts are that no one ice box conversion system fits all boats or meets all owners needs. Another thing to remember is that the efficiency of all refrigeration systems are not the same. The efficiency of an engine driven or large 12 volt system is rarely of concern because they both depend on the engine running. The concern with these large holding plate systems was how much energy could be transferred to the plates in a short period of tome. When it comes to these new small new variable speed 12 volt Danfoss compressors run time is no longer important. The System Coefficient Of Performance (SCOP) now allows manufacturers to have higher efficiency than was possible with the older compressors. The Isotherm holding plate systems are a good match for small boxes of less than four cubic feet in tropical, they even say this in their installation guide. One key to a holding plate’s performance is the amount of surface area must be able to absorb the heat capacity equal to the compressors output. In my opinion Isotherm no longer has an interest in after market support and their designs are for the cooler climates. If you want to compare the Danfoss compressor systems connected to holding plates I am sure the Technautics Cool Blue would be the most efficient in comparable boxes.
History has proven that pumped water cooling these small compressor systems results in poor system reliability. The water pump systems are generally less efficient in warm water than air cooled and destroy the energy advantage of the of the variable speed compressors.