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  #1  
Old 10-25-2011
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Question Help with refrigeration decisions...

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.

Original refrigerator:



Refrigerator components:



Cold plates:



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.

Keel cooler:


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 and Oddasea (click for article links) give some good insight into these units:

Quote:
"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:








Freezer box:



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?

Thanks!
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Last edited by Beersmith; 10-25-2011 at 04:01 PM.
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Old 10-25-2011
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I'd say 3" is not really thin for insulation You could offset the heat gains buy using well insulated and air tight lids. Try and determine the cubit foot size of the boxes. Just about all the split units (evaporator and condenser) are designed for DIY installers. Depending on the size you could do the freezer with a single evaporator and use passive exchange between the boxes for the re-fridge side. Or go with separate systems if the boxes are large. I like keel cooling but worry if the boat is "parked" for long periods, marine growth would reduce it's heat exchange properties. Battery power and charging requirements will be need to be met since the engine is not going to do the "work" "Cold plates" are what you had, (those block like aluminum things you removed that are in your 3rd photo) I doubt they are re-usable. New holding plates are the way to go if you feel you will be running without battery power while sailing for a day or two. The do just what the name implies. "holding" the temps while the system is off.
Hope this helps!
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Old 10-25-2011
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I am thinking your refrigeration system has a compressor that is driven by your sailboat engine and therefore uses the same refrigerants that automobiles use. Since your refrigeration system was installed in 1991, I believe it would use R12 (freon) as 1993 was the year that air conditioners in automobiles switched to R134a. The problem is that R12 is now very expensive because it is no longer manufactured because R12 causes ozone depletion. You can convert a R12 system to R134a, but the dryer has to be replaced and system flushed to remove the lubricant (I think acetone is used), which is replaced by a synthetic oil. Also, the seal on the compressor is probably old enough so that it will leak refrigerant, which is probably why the present system does not work. If the system used a sealed compressor driven by electricity only, then as long as the motor is good, the system should work. Check with the refrigeration technicians and see what they want to convert from R12 to R134a.
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Old 10-25-2011
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I am running an Adler Barbour Super cold machine and I think it is great.

Keeps a big fridge really cold a small freezer unit frozen making two trays of ice a day.

Box is top loading and well insulated about 4 to 6 inches. Air cooled too not watercooled.

FT liveaboard in the Caribbean.
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Old 10-25-2011
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I've been thinking about redoing the refrigeration on my boat also, and I've been looking at those portable units semi-seriously (I'm not quite ready to actually change anything just yet, so "semi-serious" is about as far as I'm gonna go just yet). I thought I might mention a few other advantages to these units (at least as I see it). First, if the thing breaks you can take it to someone, rather than having to spring for a service call. Even if I wound up working on it myself, it would undoubtedly be easier to tinker with a portable unit than to crawl around the bowels of the boat in various yoga/contortionist positions. Second, if a portable unit does eventually become unserviceable, replacement would be a snap (as long as I could find a new one close enough to the same size. And lastly, for someone like me (and probably 90+% of the rest of us) who only "cruises" on weekends or for a few weeks during the summer (if that), being able to take the portable unit home when it isn't in use, load it up the night before I head to the boat, and let it cool itself (using the 120V at home) before I schlep it down to the boat in the morning would prevent me from having to either keep the fridge running on the boat while I'm not there, or starting the weekend with a "warm" fridge and using a big chunk of my battery capacity chilling it down.

I also figured I could make a nice little spot for such unit in the galley of my boat, constructing it in such a way that the cooling air would circulate in and out of the engine space/lazaret (where and air-cooled compressor would be anyway). This would also allow me to use the cabinetry surrounding this area as added insulation.
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Old 10-26-2011
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For full time tropical cruising I don't think 3" of insulation is enough. There are some that are happy with 3" of insulation in tropical use but their fridge/freezers would cycle a lot less if they had more insulation.

I helped a friend install a Frigoboat with a keel cooler on his Westsail 32 - the box already had about 5" - 6" of insulation and a tight fitting lid and was well built but was only an icebox. It worked out very well and he is very pleased with the installation - he is now in San Diego and heading farther south.

In my own boat I chose an Engel portable as my "icebox", which is 5.8 cubic feet in size and well built internally had very little insulation. I decided that it was both easier and less expensive to buy the Engel, placed elsewhere and use the original icebox for dry food storage. I did not find an Engel user that was not satisfied. They are the most energy efficient of all the brands of portable units available. Consumption is about .8 amps as a fridge and 2.5 amps as a freezer - about 20 AH/24 hours as a fridge only. The unit I have is newer than the one pictured (MT-45 I think) and has the same compressor but a more rugged exterior that cannot rust - the MT-40 pictured below.

If I had a boat like yours I would go with the Frigoboat and a proper box. My boat is a CS27 and my goal is minimal consumption so the Engel was a better fit for me.
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Old 10-26-2011
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Forgot the pic.
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Help with refrigeration decisions...-img_5735.jpg  
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Old 10-26-2011
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Good info mitiempo. Question: How well does the Engel hold the cold? Doesn't look like it has any decent insulation...so does it run all the time? 20ah a day?
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Old 10-26-2011
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Mine cycles probably 1/3 of the time, maybe a bit more when it is warmer. Holds the cold well. Based on all I could find, from owners of Engels they have no issues and are long lasting, durable units.

Here's a thread on Sailfar about them Refrigeration, Engel users, and others.....
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Old 10-26-2011
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Good thread, mitiempo, thanks. Those Engel's sound mighty cool. My wife would be overjoyed if we had refrigeration on our boat. Our 2-3 week trips in the Salish Sea have thus far worked OK with ice and doing without, but my wife is a gourmet cook and her options would explode if she could keep things cool.

The icebox on a Gulf 32 is freaking huge. Ridiculous really. It is not very well insulated, of course, and so there's a dilemma. I could modify the compartment to accept one of the Engel models that has a removable lid and drop it into the icebox space, but then I would probably lose a fair amount of square feet.

Putting it anywhere else would certainly rob us of space too. But the technology and price are compelling.

Hey, I don't need more projects people!
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