This is a blog post I just made, and I would appreciate any help from the Sailnet readers as I ponder the direction I am taking for refrigeration on Windsong:
The system that came with the boat is a 1991 model Seafrost system with engine driven and AC/120v compressors. There is a larger refrigerator and a smaller freezer box which seem to be stock iceboxes on a Downeaster. The system was not functional when I bought the boat, but serviceable. I decided to get rid of the whole thing and start anew for a few reasons. First is that the engine driven compressor is great for a charter boat, or someone who will be motoring a ton anyways. I won't be, so I need a different kind of compressor. The AC compressor is a great ad-on but only works when attached to shore-power, of which I won't be when cruising. I won't be using the freezer as mentioned above, so I will just use the freezer space for an icebox and extra storage.
In addition, the existing iceboxes are less than adequately insulated for tropical cruising. Most sources recommend at least 4 inches of polyurethane foam for insulation, mine has only 3. Of course there are other types of foam and vaccum packed insulation that require other thicknesses, but the poly is what I'm going for. I will most likely leave the freezer unit as is, and just beef up the refrigerator icebox.
So now I have two tasks:
1. Figure out what kind of refrigeration system I want
2. Plan and execute the rebuild of the icebox
I have narrowed my decision of the refrigeration type to a few different unit types. The first decision is whether to go for an integrated/traditional style marine refrigeration system, or a stand-alone/powered icebox system.
The integrated system is similar to the one that came to the boat, but with different compression systems. The choices are air cooled, water cooled, or keel cooled compressors. Since I will be cruising in the tropics, I've eliminated the idea of an air cooled system like most people have. While they are cheaper and easier to install, they require more energy and are less efficient in tropical/hot climates. The water cooled units are much more efficient since the water is generally cooler than air and transfers heat easier. However, the same idea can be applied using the newer keel cooled compressors that eliminate the need for a water pump (which draws a bit of energy itself). The keel cooled compressors have gotten great reviews by their users
, and are even highly suggested by the author I have learned so much from: Nigel Calder in his Boatowner's Mechanical and Electrical Manual
, practically the bible for all marine systems. Basically, the keel cooled compressor brings the refrigerant lines to the water (instead of the water to the compressor via pump) via a plate or thru-hull below the water line. Some of the units I am considering that have received great reviews are Frigoboat, and Isotherm
kitsets. Here is a link to a Frigoboat
installation by Soggy Paws: click
The other direction I could go is that of a stand-alone refrigeration box system. I have recently read about these boxes and have been intrigued by the endorsements a few respected blogs have given them. Boat Bits
(click for article links) give some good insight into these units:
"I’d known about mobile refrigeration units since I was a teenager in the Boy Scouts. 4x4 camping, expeditions, and humanitarian aid projects often equipped themselves with vehicular refrigerators - highly efficient integrated units with DC power supplies, high-tech insulation, and modest but acceptable internal space. Hell, a lot of fellow sailors on smaller boats had them. I’d somehow never thought about them on a larger boat - namely “my boat” - because mine had a built in fridge. But while I was researching boat refrigeration, I stumbled upon an old post on Boat Bits that reminded me how sane of an idea it was. The kicker isn’t just efficiency, as important as that is, its long-term reliability. Boat fridge units are notoriously unreliable and inefficient, often requiring the engine to be run to generate enough power (or in extreme cases to even produce refrigeration power at all!). In the hotter climes its not uncommon for them to be breaking down within months of the last repair due to high duty cycles and thermal overload. But these mobile units were designed specifically for these harsher environments, with insulation and refrigeration mechanics well matched to each other and designed purposely to deliver 100% performance in blistering 43.5 C (110F) heat while consuming a very modest power draw suitable for solar or small vehicle power. The Boat Bits article specifically mentioned some Aussies who had excellent and highly reliable self-contained fridges aboard.2 And I just so happened to have a fantastic magazine at hand which reviewed the most revered of these units worldwide: Overland Journal." - Oddasea
These are essentially powered coolers with refrigeration and freezing capabilities that run off 12v/DC or 120v/AC power. They are touted as being extremely reliable, rugged, and energy efficient. They were originally made to transport medical equipment and other supplies to remote areas like deserts, and to work no matter what. One of the more popular manufactures of these boxes is Engel, such as the unit below. However, the units mentioned in the Boat Bits and Oddasea articles seem to be more rugged.
The trouble with these units is that I will need to find a place to put it. They are obviously air-cooled, but apparently can withstand high temperatures and still function efficiently. However, it doesn't seem I can just sink the unit into the ice box space and still be able to reach the controls and have enough air flow around it for it to work properly. If I wanted a unit like this, I would need to seriously modify the existing icebox area or find a new place entirely to keep it. This is my theory anyways, and if anyone can tell me otherwise I am all ears. These units have major upsides though, particularly the fact that they have freezer capabilities and are supposedly extremely reliable.
If I were to go the keel-cooled integrated unit, I would need to proceed with the icebox upgrade. If I were to go with the box style unit, I would need to modify the icebox area to contain the box or find another space for it. All of which will require some cutting, grinding, glassing and sanding. I want these done before I clean up the interior and paint so I can move aboard.
Here is a look at the existing iceboxes. As you can see below, the original refrigeration box is well designed, just too thin in the insulation department. There is also a large hole in the side that was covered by a teak panel, but left void of insulation. I plan on filling in this hole if I go with the integrated unit:
I am currently leaning towards the keel-cooled unit unless I have a great lightbulb moment on how to carry the box unit aboard without giving up too much space.
Please chyme in on your thoughts and if you were in my shoes, which direction you would go. Also, would my old Seafrost system have any value to be sold?