Keel Coolers

[ssullivan]

Dick once whispered in the wind:
A freezer with a sustained temperature of 25 degrees F. is not a freezer for food as Enzyme activity at that temperature can lead to the deterioration of food quality were quickly.

Hmmm... question:

Enzyme deterioration is not nearly as bad as bacterial contamination/growth. I recently ate meat that had been in our junky Alder Barbour "freezer"/condesder for over a month. The meat was definitely not good. It lost a lot of its flavor, turned grey in color, and tasted a lot like something you'd eat in a lousy restaurant.

My quesiton is... is there anything so wrong with this meat, other than a loss in taste and nutrition from enzyme activity?

The quesiton hits home since I am dropping a couple thousand dollars on a used Technicold system shortly. The Technicold system has a 0 deg freezer plate and a 26 deg refrigeration plate. Given the 10 deg difference in temp in the icebox, this results in an icebox temp of 10 deg in the freezer and 36 deg in the refrigerator. After reading this thread, I'm thinking my food will go bad. Could they sell such plates if they didn't work, adequately?

Thanks

[GordMay]

See the new article “Frozen Food Safety”, posted under “The Galley”
at: http://www.cruisersforum.com/showthr...&threadid=2982

[Dick]

Sean, I do not know at what point in time or at what temperature meat or other food product will spoil in a freezer or when food looses its nutritional value. Having owned separate home freezers for fifty years I now something about frozen foods and how time effects their taste. These freezers were operated in a temperature range of +4 to +15 degrees F. Living in the country I purchased a hanging quarter or half a beef cut, rapped, and quick frozen. Beef stored at my freezer temperatures were generally good tasting for three to four months.

My sailboat has a small freezer with two opposing +10 degree holding plates connected to both an engine driven system and a air-cooled Adler Barbour BD 2.5 condensing unit. When running the refrigeration system off the engine drive the freezer temperature drops to zero then rises to a high of 20 degrees if the engine is stopped for 24 hours. Running the refrigerator only from the 12 volt AB with the thermostat set to zero and compressor cycling it will maintain a ten degree temperature differential. I built my first holding plate in the 1950’s to use as a ground air conditioning unit for aircraft and another 200+ plates for boat refrigerators in the last twenty years.

I do not think that you will find a conventional holding plate system in a boat that will maintain a zero degree F. box temperature as recommended by the government do to the temperature swing when the compressor is not running. A system with a compressor that can run a few minutes every hour can maintain the box at zero and below even when a holding plate’s solution is set to freeze at +10 degrees or even +26 degrees F.

Most people do not understand the history and function of a holding plate, they are not better than other types of evaporators they are energy storage devices. In some applications a holding plate is less efficient than a conventional evaporator if it is so small it lacks at ability to dissipate the capacity of its refrigeration systems compressor. In the 1940’s and maybe earlier holding plates were used on city delivery trucks to store energy because trucks did not have on-board compressors back then. Capturing and storing excess energy is the only purpose for holding plates in a boats refrigerator and not because they are more efficient. With the improvements in DC power systems on boats and the new generation of more efficient compressors there is little need today for holding plates. There are some companies selling small 12 volt systems with small holding plates that I believe is only a sales gimmick.

Sean, Technicold has a good system and there are boats that have large refrigeration needs that can not be achived with evaporator type systems which require continuous power all day.

[GordMay]

Freezing (to a constant 0 degress F or less*) preserves food for extended periods, because it prevents the growth of microorganisms that cause both food spoilage and foodborne illness.

Being able to freeze food, and being pleased with the quality after defrosting are two different things. Some foods simply don't freeze well. Examples are mayonnaise, cream sauce, soft fruits & vegetables (lettuce) and mushrooms. Raw meat and poultry maintain their quality longer (when frozen) than their cooked counterparts because moisture is lost during cooking.

Freezing can damage some foods because the formation of ice crystals causes breakage of the cell membranes. This has no adverse effects in terms of safety, (indeed some bacterial cells would also be killed), however the food loses its crispness or firmness.

Foods with higher fat contents, such as cream and some sauces, tend to separate when frozen.

Commercial freezing rapidly freezes foods so that smaller ice crystals are formed. This cause less damage to cell membranes so that quality is even less affected.

* The inability of Holding Plate freezers to maintain a constant temperature (<0 F) is one of the system's major disadvantages. It's simply not an effective (safe) long-term storage solution.

[Strygaldwir]

Time for a quick update. I always find it useful to see periodic updates concerning the longevity and durability of the items placed in use.

It has been 3 1/2 years now on the Keel coolers. I was inspecting and replacing the zincs in them this past weekend. The zincs were a bit powdered on their surface and they were about 50% used, but I had gone about a year without replacing them. The cooler both appear to be in outstanding shape, no noticeable wear on the exterior. On the interior, the tubing has a few green spots that I expect will clean right up.

Energy consumption is higher than I originally estimated, it appear to be something on the order of 130 amp/hours per 24 hour period. (This is after I sent in my Link 2000 to have it recalibrated!)

[Talbot]

Originally Posted by Strygaldwir

Energy consumption is higher than I originally estimated, it appear to be something on the order of 130 amp/hours per 24 hour period.

Is this a total for both a fridge and a freezer - both using keel coolers?



How big are they?

[Strygaldwir]

That's the total of both. They are totally separate units, compressors sit side-by-side, keel coolers sit slightly off-set from one another. I used LOTS of insulation on the boxes and I don't really set my freezer as low as I have heard it is supposed to be set. I only have it set to 25 degrees f. The refrigerator is only set down to 40. The compressors are the f-50 (BD-50s). The evaporator plates are the long plates by Frigoboat. I don't exactly remember the size. (maybe 18" x 30"?).

The freezer is maybe 2.5 cubic feet internal space. The refrigerator is maybe 6 cubic feet. I measured them some time ago, but I added some additional insulation to the interior of the freezer to cut down on the size.

[Talbot]

Originally Posted by Strygaldwir

That's the total of both.

That works out at 2.7 amp/hr continuous per unit, which is very reasonable.

I don't really set my freezer as low as I have heard it is supposed to be set. I only have it set to 25 degrees f. The refrigerator is only set down to 40.

This helps to explain your low power consumption. The freezer temperature will definitely reduce the length of time you can keep stuff frozen I have my home freezer set at 1.5 deg F and fridge at 37 deg F. Which is supposed to be optimum for life of stored stuff.

(thats -17deg C and 3 deg C for Europeans)

IMHO you can lengthen stored stuff times by use of vacuum packing.

[Strygaldwir]

This is not really an excuse, but we really don't use the freezer for that long a term of storage. Anything in it will be eaten within 30 days, or thrown out. We have yet to throw anything out. Making ice cubes takes a bit longer than our home box. But what we do is freeze a couple of trays and dump the cubes into a zip lock bag. When we have others over there are generally enough cubes for everybodies drinks and such.

So, for slightly less longevity in food, and ice cream really not storing well, we don't consume energy that is difficult to generate.