Originally Posted by RTB
I installed an Isotherm system myself about 10 years ago. It was a "Self Pumping (SP) version with "Automatic Start Up" (ASU). The SP bit meant is used an in-water heat exchanger that circulated coolant by convection--no fan. The ASU bit meant that the compressor would kick into high gear if the engine came on so as to freeze the cold plate faster.
The worst of it was changing out the galley sink drain thru-hull with a bronze one that housed the heat exchanger. Hasn't fouled or corroded in 10 years. It is a fairly compact thru-hull and wasn't any big deal to install. The only other large hole was a little over an inch to accommodate the special fittings that allow the system to be precharged. Other than that it was a matter of less than a dozen screws to secure the compressor, cold plate, fuse, and controller and running wiring.
Bottom line: The unit was more expensive than an air-cooled refrigeration system, but it is extremely compact, quiet, and apparently very efficient. I once ran it for 4 days on battery power to see how long it would take to discharge my battery bank. I wasn't running any other loads, so I would estimate that I could go 2 days on 3 fully charged 105 AH gel cells under realistic conditions (house lights, electronics, windlass).