Which new refrigerator system?

[s/v Jedi]

I think everyone can take Richards posts for fact because he's a pro and everything he writes matches what I learned the hard way !!

We started off with a Glacier Bay system with holding plates and a huge 12V motor driving that beast. It took 70A for the first 20 minutes or so, quickly draining batteries. Every two weeks (or more) I needed to put the gauge set on to check it, top it off etc. Every year or so the compressor shaft-seals started leaking and a rebuild was needed. I carried 2 compressors and one was out for repair most of the time. It was hell.

We now have Frigoboat. I think all units that use the Danfoss compressors work alike and have equal performance. I also see that most evaporators look alike and guess they have more or less equal performance. The differences are in the condenser like keel-cooler vs fan vs water-pump. I think we are lucky with our keel-coolers as we have 3 units in continuous use for 4 years now with no maintenance except defrosting the evaporators every year or so. I read info on bad keel-coolers and hope they started making them better.

Now, a step away from scientific approach: we bought 50 pounds of beef tenderloin in Venezuela, vacuum packed it all and put it in our freezer. Our freezer switches on at -12 C and off at -14 C. Six months later, the tenderloin was as good as the day we bought it, without freezer-burn (I think the vacuum packing helps). With our old system we couldn't do that because it would brake down every couple of months with all contents getting spoiled before we could repair it. The new system runs for a total of 20 minutes each hour on lowest speed setting. Volume is just under 5 cubic feet, largest flat evaporator (Frigoboat), air and water temp 25-30 C in the Caribbean.

ciao!
Nick.

[hellosailor]

So Richard, what would you recommend by brand name for dc-powered refrigeration? Despite Nick's love for Frigoboat, my impression is that you don't particularly like them?

[gbanker]

I'll chime in again: I concur with S/V Jedi, the Frigoboat units (refrigerator and freezer) on our boat have worked flawlessly and I can recommend them highly.
PS this is the first boat on which I have eaten ice cream on a passage!

[Richard Kollmann]

The Best way to answer hellosailor’s question is I recommend all companies presently marketing refrigeration systems for boats.
I do not mean to say that each unit sold by these companies will fit the conceptual needs of each boater or that all equipment being sold is without problems. If you have not watched the complete slide show “What Works And What Does Not “ on my web site it takes you through the equipment selection process to achieve an adequate boat refrigeration system. I have listed a couple companies names in slide show but that does not mean I would purchase all products they advertise.

[Badsanta]

I have been looking at the SeaFrost for the past few years at the boat show. What I like is the holding plate. Well its not a holding plate to freeze but it has a thick stainless steel plate compressing the cooling lines about an inch thick works like the thin stamped evaporator but is ice pick proof. Any experience or thoughts.
Thanks AL

[Cowboy Sailer]

Richard,
Have you had a chance to evaluate the Stirling free piston refrigeration system yet? I would really be interested in your opinion of them.

Keep cool,

Jerry

[Richard Kollmann]

Badsanta, There are many different types of refrigerator evaporators. Using stainless steel over a copper coil to protect refrigerant coils is done in fish boxes, but if complete coil is not in contact with plate heat conductive is not as efficient. Frigoboat has a stainless plate with a standard aluminum roll bond evaporator behind it. The SeaFrost’s stainless plates use a heat conductive paste to increase the heat transfer efficiency between refrigerant evaporator coil and stainless plate. If you have one of the small U line ice makers onboard this heat sink paste is used between ice tray and evaporator plate. Heat sink past is why these small ice makers can produce 25 pounds of ice per day. I have no experience with SeaFrost’s thin plates. Seafrost plates can be sized to fit any box and are not subject to the same aging or puncturing problems experienced by aluminum evaporators. Remember the compressor’s output Btu capacity must be large enough to handle a given box’s heat load. When selecting an evaporator and expansion device they must be able to handle the planned Btu capacity of compressor. Selecting too large of a compressor or setting its speed too high for the size evaporator selected will result in poor energy efficiency.

[Richard Kollmann]

Cowboy Sailer,
The Sterling pumps were used in an icebox conversion demonstrated at boat shows a couple of years back but apparently not a success because the company shut down. They had a couple of units installed in boats that were to keep as updated on their performance but I never heard any more about those systems. For one of these Sterling units to equal the performance of existing 12 volt units they need to operate successfully 2,000 to 4,000 hours per year in a full time cruising or live aboard boat.

Pure refrigerant CO2 reported as more energy efficient and friendlier than the blended refrigerants we will be forced to when R22 and 134a are eliminated because of global warming fears. Coke and others are converting vending machines to operate on CO2 refrigerant. There are compressor companies currently selling CO2 compressors even Danfoss may be offering a compressor for CO2 refrigerants soon. The Europeans are ahead of us on plans to eliminate 134a refrigerant and replace it with CO2. The only place where the Sterling Free Piston seems to be in use is in a very small portable cooler.

[hellosailor]

Richard, your mention of heat sink paste is interesting. I wouldn't have thought it made that big a difference, but then again, since the contact "enhancement" that it makes with computer chips is fairly ciritical to their operation...I guess it obviously does more than one might think.

Two alternatives come to mind, what would you think of these?

1-Sandwich the coil (with paste) between two metal plates, and compress slightly in a hydraulic press, then bond in the compressed position, so that the tubing was partly flattened to enhance contact area.

2-Replace the tubing with a flat billet of copper, drilled across with passages and fitted with end caps (i.e. "U" tubes) so that the "tubing" and "plate" were one piece of metal, with no transfer issues?

Obviously both might have some costs issues...but the copper billet might not be so expensive if the labor were written off as "hobby time". Or a less expensive metal used, perhaps.

[s/v Jedi]

I see many cruisers whacking at the frost buildup at the evaporators, using putty knives and even ice picks. I really don't understand this... is this how they defrost their domestic fridges too??? We just shut it off, transfer contents into cooler and let it defrost by itself. If we're in a hurry, we put a fan in the opening and if we are really pressed by time we use the hair dryer.

If you don't take the ice pick to it, the "cheap" aluminium evaporators are just fine. Use nylon washers/bushings to isolate the stainless screws from the aluminium and they last for ever.

I have another tip that I learned from another, forgotten cruiser: make a floor in the fridge with dry-deck panels except for a small spot in front where you put one of those no-drip sponges. Wring out the sponge every couple of days and everything stays dry and clean. The dry-deck panels are treated to resist mildew.

We tend to mess up the freezer, pulling stuff out while searching for what we need and throwing it all back in. I put the dry-deck panels there too to protect the inner lining. Love them!

cheers,
Nick.

[bobfnbw]

Nick, what type of evaporator do you have from frigoboat, the stainless steel or the aluminum one?

I am leaning towards frigoboat, and like the ss evaps. Are they more or less efficent do you think ?
Thanks
Bob

[s/v Jedi]

Bob: from what I wrote you could have guessed it: the aluminium ones. We have two boxes with a flat plate that we bended ourselves, good instructions are included (don't forget the heat-gun / hair drier part!). One box which is mainly the fridge has their biggest loop/bin evaporator that we fitted horizontal at the top of the box with the plastic lid. We use it for making ice.

I think the s/s versions are less efficient but have no actual knowledge on these. They look smart but I don't care about the looks here...

ciao!
Nick.