Keel Coolers

[markpj23]

Don't auction off that condenser yet...

It seems logical that you could replace the condenser raw water cooling loop with a plumbing arrangement like you describe. If I understand you correctly, you would run refrigerant piping into an immersion tank - either your potable water or fuel tank. So the circuit simply goes: compressor - immersion tank - TXV - evaporator - back to the compressor.

I think you'd have to be carefull about the added volume of the system to be sure that the compressor was adequately sized for the amount of refrigerant the new piping volume would require.

You would also need to insure that the temperature differential across the immersion tank was acceptable. Too hot or too cool would reduce efficiency.

As for the fuel tank, I assume (hope) you mean diesel. It would certainly provide an adequate heat sink, but warmth helps all the fun stuff grow in diesel. Not sure if it would be worth the added muck in the tank. Or the added difficulty in cleaning your fuel tanks, now with the added risk of disabling your refrigeration if you ding the reefer line.

At some point the cost-benefit of that extra thru-hull as opposed to the custom refrigerant piping would have to be considered.

All options discussed in this thread are technically feasible. Like everything else, each option has its benefits & drawbacks.

The things we'll do for a cold brew...

[ssullivan]

Yup.... after reading all this and really giving it some more thought, I am a bit nervous about doing anything to modify the system, given that it was designed to run with very specific paramaters.

Also, Mark was right about the drinking water going through non-drinking water approved plumbing. I wouldn't plumb my fresh water system with anything less than drinking water plumbing, so this would leave a big source for unknown materials in the water.

I may do as Bill (of Makai) said. I think I'll have to T off an existing thru hull. I could easily T off the forward head intake (provided it can easily provide the GPM required). Since the refer will only run 1 hr per day, when I turn it on, the forward (or crew) head can be "closed" during that time period. Not a big deal, and no new thru hulls.

Now... what about the exit? I have 3 exit (above waterline) thru hulls right next to the are the compressor will sit. Can I just T again into the bilge pump's or shower sump's hose and install a check valve so water doesn't go back down into those items?

[GordMay]

I don’t recommend the use of Check Valves, which are not normally required on low-pressure drains.
Groco makes the “RWM” and “DM-5-1500" Manifolds, which can be utilized to combine several drains into a single through-hull discharge.
Goto: http://www.groco.net/
Or
http://cruisersforum.com/photopost//...php?photo=1420
and
http://cruisersforum.com/photopost//...t=7&thecat=500

[Loup de mer]

Thank you Jack! Though still a bit unsure I will think about it because I really don't like to drill another hole!

Wolfgang

[ssullivan]

GordMay once whispered in the wind:
I don’t recommend the use of Check Valves, which are not normally required on low-pressure drains.
Groco makes the “RWM” and “DM-5-1500" Manifolds, which can be utilized to combine several drains into a single through-hull discharge.
Goto: http://www.groco.net/
Or
http://cruisersforum.com/photopost//...php?photo=1420
and
http://cruisersforum.com/photopost//...t=7&thecat=500

Thanks for the heads up, Gord. Very useful links, as always!

[Dick]

I have followed this thread with great interest having seen these different methods of refrigerant condenser cooling mediums in operations, but no one has mentioned all of the adverse effects of using water as a cooling medium. Most boaters understand the problems with circulating water with a pump, restricted water flow and poor reliability but what about the damaging effect to aluminum tanks, or the boat’s aluminum hull or total destruction to the refrigerant system caused by electrical discharge?

It is a fact that water cooled units do experience material loss do to electrolysis. It is also a fact that Danfoss BD compressors do discharge small amounts of current into the seawater causing failures at the point of voltage leakage. On circulating water systems it’s the seawater condenser that fails, on keel coolers it is the line or block that fails, on aluminum tanks it’s the tank or hull that looses metal. A few of the responsible refrigerator manufactures address the electrolysis problem by adding Zincs to the heat transfer units but most ignore the problem because the rate of metal loss is not predictable on all boats do to their use.

I have three questions for boaters with water cooled condensing units; After how many refrigeration operating hours do you replace the zinc on your water cooled unit? How many hours is the refrigerator run while connected to shore-power, between zinc replacements? Why do you believe that water cooling of a small 12 volt unit is more efficient than air cooling?

[Talbot]

The thread was originally about keel coolers. As these dont pump seawater, but use the compressor pump to cycle the refridgerant through a bronze heat sink in the water (fitted with an anode), I dont understand how the seawater can have any impact

I certainly would not pump saltwater through or use a heat exchanger to pump cooled fresh water, as the additional pump would substanially increase power useage.

[Strygaldwir]

Dick;

I have the Frigoboat Keel coolers, so I guess that qualifies as water cooled condensor.

I replaced the Zincs after 6 months. They were noticably worn.
The Frigoboat system runs continuouly, sort of. The Freezer compressor is on about 14 hours per day, The refrigerator compressor is on about 8 hours per day. This is a rough estimate given regular inspection of the controls.

These are DC systems, so, I am not sure if the issue of connection to shore power applies. They run with the boat in water, out of water, shore power, or no shore power. I have yet to deplete the batteries to the state where they will not run.

My refrigeration consumes about 32 amp hours in a twenty-four hour period. This is about 10 amps for the refrigerator and 22 amps for the freezer.

I believe the water cooling is more efficient because the transfer of heat through water is about 16 times greater than air. I believe water is more efficient because when I was on the hard, my refrigerator was on for closer to 20 hours per day, albeit at a low speed setting. My Freezer was on 24 hours a day, at its maximum speed setting. This is except for the couple of days that the outside temperatures got down to freezing. They were both off for longer periods during those couple of days. This is not a definitive test or comparison of the two approaches. My keel coolers are not designed to be air heat exchangers. But, the comparisons my give some indication of the relative efficency between the two media. My boxes are both rather large and just on the edge of the recommended capacity of the keel cooler solutions. I was beyond the capacity of the air cooled solutions, even though I believe they both use the same compressor (BD 50)

The zincs cost me about $4 each. I have two coolers, and they take two each. I didn't have the boat in the water when I changed them, but I could have changed them with thee boat in the water. They are simple hex screw arrangements. I suppose I could tie them into my bonding system and use that zinc, but I use them in my SSB counterpoise system and I wanted to keep the two isolated. But, that's a different story I suppose.

Hope this helps

Keith

[Dick]

Keith, thank you for taking the time to respond to my information request. It is difficult to get good information on the reliability and service life of boat refrigeration systems do to the various applications of it. The boating equipment industry provides no service bulletins or feed back on its equipment reliability. Creative marketing is what sells refrigeration, not its performance or longevity. The internet is a great source of information but ask a question on a forum about a particular system and someone says they love theirs. In between refrigeration books I collect information for future additions of the books. Technical books need revision services to keep material up to date I do provide this by maintaining an information web site. http://www.kollmann-marine.com


Keith, your response tells viewers several things in general about your boat and how a refrigerator/ freezer selection can be correct for a boating needs. From the information you provided your boat must have two Frigomatic K50 compressor and each has a Veco keel cooler condenser with SSC compressor speed controllers installed. The boat is a Privilege 37 and operated in tropical waters out of South Florida.

Your reported 60% duty cycle on the freezer is a good duty cycling time for warm day time operation especially if the SSC has the compressor running at one of its slower speeds. The refrigerator box cycling time is also good. There are four new automatic compressor speed controllers with each optimizing the compressor’s efficiency to the Btu capacity day or night as temperature conditions change. I would question your daily refrigeration amp-hrs used but the important fact is you are satisfied with your boats DC power grid to deliver all the daily DC power you need.

In Hollywood FL. on a boat you would have to be at a dock with shore-power. As to problems with keel coolers as long as you maintain the zincs you should get many reliable years of service from these refrigeration systems.

Keel coolers connected to Danfoss BD compressors do have a problem with premature failures that do destroy the complete system. No one knows how serious these keel coolers failures are but they do exist. I have been involved in two keel cooler failures and have advised total system replacement on others when compressors failed. Veco must have also recognized the problem as they have made three changes to their coolers. Their first cooler exposed the tube to seawater, the second added two zincs and the third added a grounding lug to be wired to the battery ground. In the best conditions a keel cooler could out last the compressor that appears to have a twenty plus year service life.

Most of the boats I am ask to look at the refrigeration systems on are only passing through Ft Lauderdale so it is impossible to keep track of their systems history. It there is to be a serious problem with seawater condensers it does not occur in the first two years. The metal remove from any of these seawater condensers is a slow process but boats used as live-aboard, or boats connected to shore-power, or have onboard generators seem to have the greatest risk of failures.

Here is an example of a local 46 ft. boat with two systems like Fred’s. I was asked to check the installation and found the ground wire from the Veco cooler grounded to the through hull grounding system instead of Frigoboat’s recommendation to connect it to battery ground. Two weeks after the systems were installed, when the boat was being prepared for a three week cruise to the Bahamas all zincs were checked. All four zincs on the keel coolers were ½ eaten away so new ones were installed. The ground wire was also connected to the battery instead of the grounding system. After three weeks the zincs were eaten away and replaced again. The last advise to the owner was that no serious damage would have been done to the system in this short time peiod but because the boat spends time connected to shore power and has an onboard generator, a shore power and generator Isolation Transformers need to be installed.

[Strygaldwir]

Dick;

I did not know you were the "Richard" from the Kollman site; I rebuilt my boxes based upon the model you said works on your website. Thanks much! It really does work. It took a bit to maximize the insullation, some of it was a compromise. I was not able to do 6" of extruded polystyrene all around, but on 90% of areas of the boxes I was able. I did use alluminum foil for coating and I was able to seal them with a layer of 3 mil plastic sheeting. Additionally, in the freezer I added fiberglass batting and the expanding foam to give additional insulation in irregular areas.

During the winter, I am down here in Florida, I will be heading to the Bahamas in the next couple of weeks. During the summer, I was up in North Carolina. I did not bring the boat down until late December, so I did get to experience some of the cold in the North. That may have skewed my obervations slightly.

I did not complete my freezer re-insullation until late August. It was still a bit warm up north, but not as bad as in the summer. My amperage figures may be slightly off. The figures I observed were from watching my Link 2000 monitor. I shut off all loads except for the boxes to observe their amperage consumption. I have watched them run for extended periods. I extrapolate by oberving the total number of amp hours used over 24 hour periods of tim. As you surmize, I do have the Veco SSC (Smart Speed Control). That appears to works VERY well. Both boxes are front loading boxes. We open the freezer maybe once, a day. I do have two K-50's. A little bit expensive, and there have been a couple of "mysteries" after I installed them, but the refrigeration has been stable for about 1 year and the freezer has been stable for almost 4 months.

One variable that I did not mention was that I did not remove the cold plate inside the freezer. Since I was somewhat on the edge of the effective range of the evaporator, I had thoughts of hooking up an engine driven compressor and going through the cycling bit. So far, I don't expect I'll have to connect an engine compressor. It seems that this also has the affect of stabalizing the temperatures a little better. I have lost power on occassions, and the freezer retains its cool for a LONG time. I am uncertain for how long, but im outage was probably something on the order of 12 hours and the box temperature only got up to about 34. Every thing was still nice and frozen.

The other variable is my temperatures. I keep the refrigerator at 40, I keep the freezer at 25. That seems to be working well for me. I don't know about any issue with shore power. I have been leaving my charger off and only using shore AC. This is in preperation for going offshore. I have just installed a solar panel, and I had previously installed a wind generator. I want to be certain this will provide me with adequate DC power for extended periods, without running my engines. So far, okay. I think I'll have to add 1 or 2 more panels to meet my AC usage needs. The DC usage is doing well, so far.

I will keep an eye open for possible failure points of the keel coolers. I know 1 year is really not enough to judge reliability. I also, judging from the amount of wear on the zincs, am very happy I got the model with the zincs. I imagine there is a very good oppurtunity for galvanic action and failure.

Fair winds and good sailing.

Keith

[GordMay]

Keith:
Your fridge/freezer settings are at the maximum recommended temperatures, which does not allow for any heat rise above thermostat setting. Remember, these are the recommended FOOD temperatures.

The temperature danger zone (where bacteria grows) falls between 40 deg F (4-5 C) and 140 deg F (60 C). Keep hot foods hot - at least 140 deg F (60 C), and keep cold foods cold at 40 deg F (4 C) or lower.

Hence, a refrigerator should be maintained at 40 degrees Fahrenheit (5 degrees Celsius), and your freezer should be maintained at 0 degrees Fahrenheit (-18 degrees Celsius) or lower.

[Dick]

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. Foods pre-frozen can be stored at temperatures between 22 degrees F. and 15 degrees for two to three weeks. The US Dept. of Agriculture recommends freezer temperatures of zero or below.

The daily current draw on a boats freezer having good insulation will double when the boxes temperature is decreased by 25 degrees F. If the Evaporator or Holding Plates does not surround the frozen food product in the box must be rotated to insure it remains frozen.

FREEZER STORAGE CHART (0° F)
NOTE: Freezer storage chart is for quality only. Frozen foods remain safe indefinitely.

Bacon and Sausage 1 to 2 months
Casseroles 1 to 2 months
Egg whites or egg substitutes 12 months
Gravy, meat or poultry 2 to 3 months
Ham, Hotdogs and Lunchmeats 1 to 2 months
Meat, uncooked roasts 9 months
Meat, uncooked steaks or chops 4 to 6 months
Meat, uncooked ground 3 to 4 months
Meat, cooked 2 to 3 months
Poultry, uncooked whole 12 months
Poultry, uncooked parts 9 months
Poultry, uncooked giblets 3 to 4 months
Poultry, cooked 3 to 4 months
Soups and Stews 2 to 3 months
Wild game, uncooked 8 to 12 months

This Chart copied from USDA web site http://www.fsis.usda.gov

[Strygaldwir]

Wow. Maybe my thermostat in the freezer is off. The products inside the box are hard as rocks. (had to go look!) Maybe they could be harder? I'll have to play with the temperature a bit. We provisioned December 5 & 6th, we don't appear to have any quality issue, so far.

I'd definately not recommend anyone use our temperature settings, they just appear to be okay for us. When I lower my setting in the refrigerator, stuff sitting up against the evaporator has a tendancy to freeze. The box only goes above 41 when I accidentally shut it off. otherwise it fluctuates between 39 and 41.

I imagine if I lower the freezer temperature, my energy usage will shoot up. Details, details!

Keith

[Talbot]

If your freezer/fridge are not working consistently in temperature throughout the interior, it is worth adding a small computer fan inside the space to distribute the cold more equably. This will only draw a milliamp sized load.

[Dick]

Conventional home chest freezers use wire baskets to allow natural air circulation through out a box. A circulating fan in a freezer will not produce good results unless a series of standoff rails are placed on the walls and floor to provide a space for air circulation.
Top opening refrigerators and freezers on boats have poor air flow and therefore the temperatures will vary from side to side and top to bottom. Without the air movement in a refrigerator or freezer temperatures tend to stratify in layers. Most commercial and home refrigerators are constructed to allow the natural movement of warm air rising and cold air descending across the evaporator to tumble the air. The addition of a small fan can help most refrigerated boxes. I recommend a one inch square muffin fan that runs at all times the refrigeration is in use. I ran over two hundred test to prove what works and what does not, most are in my new 12 volt manual.
FAN TEST: The Thermostat was locked and outside air temperature maintained between 79 to 82 degrees F. for these 24 hour tests. ( I could not display the Data Charts here ) In test 119 the food product blocks the transfer of heat. In test 120 the small airflow from a one-inch muffin fan tumbling the air lowered the temperature eight degrees at the far end of the box. The fan increased the efficiency of the evaporator and increased the Btu output from the compressor.
http://www.kollmann-marine.com