1. My system design does in fact utilize a water-cooled condenser in addition to the air-cooled condenser. The water-cooled condenser consists of about 15′ of coiled cupro-nickel tube within a tube–seawater is pumped through the outside tube by a low-amperage water pump, and the inner tube holds the the circulating refrigerant. The source of the raw water is a tee off of our engine water cooling (so it only required an extra bronze fitting to access the water), and the exit for the water will be a new hole in the hull, but above the waterline at least. There is an advantage to having a dedicated hole, so that you can see the amount of flow and measure the temperature of the water to confirm the efficiency of the cooling circuit. Sidenote: interestingly, the most efficient way to interact the refrigerant and seawater is in opposite directions–which is to say that it is better to pump the seawater through the condenser opposite the direction of the refrigerant flow. There is a graph and an explanation in Calder that we can discuss (i.e. dork out about) sometime.

Potential problems and drawbacks with the water-cooled condenser: 1) saltwater can corrode through the tubing and enter the refrigeration circuit, ruining your compressor and everything else. 2) The water pump to circulate the seawater consumes ~1A, and runs for however long the compressor runs, and you strive for ~50% duty cycle, so 12 hours a day, so that’s an additional 12 amp-hours to add to your daily electrical consumption 3) the water pumps wear out eventuallly and just stop, in which case . . . 4) if the water pump stops (and there is no air-cooled condenser in the system too) then the compressor continues to drive up the head pressure in an attempt to successfully cool the system, until it breaks; unless you have a high-pressure shut-off switch, which is another element to plumb into the refrigerant loop (we don’t have this worry because we have the air-cooled condenser running no matter what)

2. Other systems prefer to bring the refrigerant to the seawater instead (our system brings the seawater to the refrigerant), and these are called “keel coolers”. Many commercially available products use this technology. Usually it takes the form of a moderately sized plate (couple inches by a foot or two) mounted to the outside of the hull, with one or two holes providing access for the refrigerant tubing to the plate. They work. Somewhere I even read about a guy that made a custom system where he essentially just ran his refrigerant lines though a through-hull and along the bottom of the boat for 10′ or so and back. I would be afraid of that tubing getting f’d! But the choice was easy for us, since any of the keel cooler systems require a pain in the ass expensive time-consuming haul-out for installation.

any other topics I would be happy to discuss?