While refitting Serengeti, our 1978 Formosa Peterson 46 cruising boat, Sue and I put proper refrigeration high on our list of priorities. We wanted the freedom to travel and stay away from docks and marinas for extended periods of time, but we didn't want to sacrifice the healthy benefits and enjoyment of fresh food. The system had to be one that we could rely on, didn't cost a trillion dollars, and hopefully would be simple enough that we could install and maintain it ourselves.
After researching our options, we concluded that 12-volt refrigeration systems provided just what we were looking for. The major components of a 12-volt refrigeration system include an icebox, a compressor, and an evaporator (the coils you see inside the icebox). The components available today are small, energy efficient, reliable, designed to be owner installed, and most require virtually zero maintenance. If you buy the right equipment, the compressor and evaporator come pre-charged with refrigerant so once you connect the two and provide power, you're just minutes away from an ice-cold drink.
|"If your plan is to convert an existing icebox into your new refrigerator, you may need to do a bit of detective work to ensure that it's sufficiently insulated. At a minimum, you need at least four inches of insulation."|
If you don't have an icebox, and you plan to build a box from scratch, you might want to pick up a copy of Refrigeration for Pleasureboats by Nigel Calder. This book covers icebox construction and many other aspects of refrigeration in great detail.
After you're sure you have a suitable box, the process of choosing a refrigeration system begins with correctly sizing a compressor and evaporator. Since the size of box you wish to cool is the primary determinant, you begin by measuring the height, width, and length of your box to ascertain its size in cubic feet. With this number, you'll be able to peruse the manufacturer's literature and correctly size a compressor and an evaporator for your installation.
A water-cooled compressor uses seawater instead of air for cooling. This improves efficiency by around 20 percent, but is a little more difficult to install because you'll need a source for water, a strainer, and an electric pump to circulate the seawater through the unit. The added efficiency resulting from water-cooling decreases compressor running time, and reduces power consumption. If you sail in hotter climes or plan to cruise the tropics, water-cooling is truly your best option; but if you have to, an air-cooled system should suffice. Some manufacturers are making compressors that are both air and water-cooled. We think these are a very good idea since you always have air as a backup cooling method should a pump fail or strainer get clogged.
The system installation begins by choosing a mounting spot for the compressor. It must be close enough to the box so that the refrigeration lines from the evaporator will reach. These are between six and 12 feet long depending upon the manufacturer and the particular model you have selected. If your compressor is water-cooled, keep in mind that you'll want to locate it so that you have easy access to a seacock for seawater.
|"If the soft copper tubing is bent too sharply, a hole in the sidewall may result, allowing the refrigerant to leak out, and then you've got real problems."|
While holding the evaporator, have your helper carefully feed the end of the refrigerant lines into the box and out a pre-drilled hole in the side of the box. Slowly feed the copper tubing into the box and out the hole while moving the evaporator down and into position in the box. As the evaporator is getting closer to the box, make sure that the end of the tubing is also getting closer to the compressor. If your lines are too long, add a gentle loop somewhere in the line to shorten it up. Attach the evaporator permanently to the box using stainless steel screws and making sure you bed them with a sealant. Mounting the evaporator and running the refrigerant lines is not a difficult process, but it is time-consuming and a bit sensitive regarding technique.
With the refrigerant lines run to the compressor, it's time to make the connection between the compressor and evaporator. This is accomplished with gasketed, quick-connect fittings that come factory-installed on the end of the refrigerant lines. These are made specifically for owner-installed systems, and make it easy for us regular folks to interconnect two precharged halves of a system without losing refrigeration gases. The result is a perfectly charged and balanced system once mated.
|"If your compressor is water-cooled, you'll also need to think about where you'll be gaining access to seawater."|
To complete the plumbing of your seawater cooling circuit you'll need a strainer, a small 12-volt water pump, the appropriate amount of hose, and an above-water thru-hull fitting for the discharge.
The final step in the installation is to provide power to the system. Today's 12-volt compressors are quite energy efficient, consuming between three-and-a-half and five amps when running, so their power requirements are fairly modest. Size your wiring according to the recommendations in the installation literature. Remember that wire size is a function of power draw and distance from the batteries. Also, be sure to add circuit protection by means of a dedicated circuit breaker.
So, consider adding refrigeration to your boat this year and save some bucks by doing it yourself. If you're a cruiser, you may also want to consider the benefits of a freezer. With just a few simple components and a couple of days work, you'll soon leave your ice-toting, soggy-sandwich days behind you.
Refrigeration by Tom Wood
Insulating an Icebox by SailNet
The Art of Ice-ing by Joy Smith
SailNet Store Section: Refrigeration Systems
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