Who provides the best 12 volt refrigeration systems?

[newhaul]

Originally Posted by OzePete

It's OK Newhaul, sometimes we have to settle for second best! (Don't tell Rich I said that!)
Not really and all that aside, you have made an excellent choice.

Cheers OzePete

that was on the Spencer. Now I am designing a new one for the defender .
I am needing a system for spill over freezer and fridge
Freezer is 1.5 cf and fridge would be 3.5 cf .
Both are going to be adjustable via a movable divider .
I'm insulating with 60 mm of Cryogel at r8 per 10mm so r48 sounds like overkill but I have the material and space to do it so why not.
The freezer surface for the plate is 14 inches by 23 inches I would like to do it with a 1 inch thisp co plate if possible and no water cooling. ( no more holes in this boat. )

[Mike OReilly]

Thanks Richard, this is very kind of you. Sorry for the delayed response, but my net access is sketchy, and I wanted to be able to respond fully. I’ll respond in the body of your message.

Originally Posted by Richard Kollmann

Selecting the Best Replacement

My short answer to your question is describe in detail the system you have and how well it performs in various weather conditions as well as your likes and dislikes. I will then recommend more than one companies above average refrigeration unit.

Long answer, I know of no Icebox conversion refrigeration unit that is not suitable for some application. With over one hundred pleasure boat refrigeration options to select from choosing the correct unit requires a number of questions answered:

1. What is size of box to be refrigerated?
Our box is currently a freezer unit (wrap around box plate) which cools the primary box. There is a spill-over “fridge” box. The primary box is perhaps 2’ x 2’ x 1’. The spill-over box is a little larger, perhaps 2x2x2.

2. Is this a single box to be used a 40 to 50 degree F cooler, or a 33 to 36 degree refrigerator?
I’m aiming at cold, but not necessarily freezing, in the main box: refrigerator temps.

3. Is this box required to also have a freezing section?
This would be nice, but not a must.


4. What size 12 volt electrical power grid is on boat for generating and storing electrical power?
We currently have a 320 amp-hr bank, with 400 watts solar and a 400 watt wind generator.

5. Normal persons onboard?
Two adults, full time.

6. Planed cruising areas?
Currently cruising Newfoundland/Maritimes. Have plans to head south (Bahamas, Caribbean).

7. Describe planed use of boat Blue water or Live aboard?
Hmmm, blue water when needed. Remote anchorage most of the time. Full time, liveaboard, currently for about 6 months/year.


8. I always leave insulation as the last question as it is the least important, but must be evaluated especially if it is 30 years old. I assume the present refrigeration unit is still running. Now today with old unit running can you detect any box exterior cool spots or condensation after cycling for over 24 hours? How much insulation in inches do you believe surrounds the box?

I don’t notice any cool spots or condensation areas on the lid. It is a top loader. The boxes appear to have perhaps 3” of insulation on the lid and cabinetry that I can see. The box backs against the sail locker and engine room. I don’t know how much insulation is back there.

[a64pilot]

I believe you can water Cool very effectively using the drinking water tank as a heat sink, very effectively.
It’s not going to heat the water, much if any at all, you likely only dumping a couple of amps max heat into the water if it’s used to augment air cooling, and that is just not much heat at all.

[chouliha]

Originally Posted by a64pilot

I believe you can water Cool very effectively using the drinking water tank as a heat sink, very effectively.
It’s not going to heat the water, much if any at all, you likely only dumping a couple of amps max heat into the water if it’s used to augment air cooling, and that is just not much heat at all.

We have been doing this for the past 12-13 years. Finally got fed up with replacing zincs and cleaning the salt water strainers. The water tank is below the floorboards and the tank side lay against the hull. 100% of the time has been in the tropics - maybe not as efficient as air cooled but it’s what we have.

Chuck
Jacaranda

[hzcruiser]

Originally Posted by chouliha

We have been doing this for the past 12-13 years. Finally got fed up with replacing zincs and cleaning the salt water strainers. The water tank is below the floorboards and the tank side lay against the hull. 100% of the time has been in the tropics - maybe not as efficient as air cooled but it’s what we have.

Chuck
Jacaranda

My understanding was that it's not actually water cooled but thermally coupled the condenser to the tank (on the outside). Which is an excellent idea, I believe.

[Richard Kollmann]

Originally Posted by Mike OReilly

Thanks Richard, this is very kind of you. Sorry for the delayed response, but my net access is sketchy, and I wanted to be able to respond fully. I’ll respond in the body of your message.

Mike, The figures I use to determine selection of boat refrigeration hardware are produced from many boaters actual experiences and not theoretical trade school or mechanical engineering hand books. If you remember Calder’s and my first books in 1983 on pleasure boat refrigeration we both copied information from industries non related to marine applications. I was also pressured or should I say tricked into to using water as a condenser cooling medium. Condenser seawater cooling is a must on large refrigeration units but it has proven to be very unfriendly for small BD size compressors. EZ Kold with an excellent eutectic plate I believe went out of business because of water cooled condensers. Their attempt to resolve the problem switching to water from fresh water tank was their last foolish attempt to save the company.

When asked for a mobile refrigeration design recommendation I size equipment for a worst case warm weather condition. The equipment selected must be reliable anywhere and maintainable with a level of redundancy. I try to recommend hardware that is available from more than one supplier. I also, as you probably know consider the Danfoss engineered compressor and module are the best choice regardless where they are manufactures.

Mike, I should have asked for more information on old refrigeration equipment size and how well it maintained desired box temperature. Now I have no way to determine aged condition of insulation. Your insulation is probably Polyurethane closed cell foam. After 30 years the closed cells tend to open and release the dry gas vapor inside allowing ambient air to replace the non heat conducting gas vapor with moist air. During the years you used the old refrigeration each time compressor cycled ON ambient air locates a cool spot and moves in. When compressor is OFF air expands inside open cells leaving moisture. This dehumidifying action over time with open cells causes insulation to be less effective. Because it has been known for many years that insulation for refrigeration is not the same a heating insulation, your insulation may be encapsulated and sealed in a plastic cover to keep out moist air.

You have control over amp-hrs and energy consumed by setting thermostats to higher than my design temperatures of freezer +15 degrees F and Refrigerator box +36 degrees F.

If your box measurements are correct, I estimate worst case 88 amp-hrs of compressor running is required per day in Newfondland waters In the month of July.

When in the Bahamas Again worst case 176 amp-hrs.

Mike, Your onboard battery capacity of 320 amp-hrs is far short of the 800 amp-hrs needed. I also recommend high output alternator and smart voltage regulator. I normally would recommend standard evaporators in each box area when insulation is questionable instead of the inefficient eutectic holding plates. So if your direct current power grid can not be increased to 800 amps you will have to live with the poorer performance of holding plates. Your other option is major cabinet work and new density controlled close cell insulation with an R value of at least R30.
The problem with the 800 watts of alternative energy wind and solar is they need battery storage capacity.
The refrigeration capacity needed for this boats upgrade dictates the need for two Danfoss BD50 powered air cooled condensing units.

If you could improve the 12 volt power grid on boat with 800 amp-hr capacity then there is more than one available icebox conversion unit available with a choice of standard evaporators. Freezer evaporator need to surround boxes content as much as possible.
For the refrigerator box I recommend a bin shaped multi purpose evaporator.
Companies that offer the Danfoss BD50 system and several evaporato are; Adler Barbour, Seafrost, Cold Eh, Isotherm., Frigoboat and Nova Kool .

If the energy demand or energy storage cannot be resolved then Technautics would be the only company I can recommend that has true holdover eutectic holding plates. It is important to understand that only when compressor is running will energy be stores in eutectic plates, this is why large power grid capacity is important.

Richard

[a64pilot]

Originally Posted by hzcruiser

My understanding was that it's not actually water cooled but thermally coupled the condenser to the tank (on the outside). Which is an excellent idea, I believe.

Quite a few people actually circulate the water, and do away with the issues of stray current etc.

[a64pilot]

Originally Posted by chouliha

We have been doing this for the past 12-13 years. Finally got fed up with replacing zincs and cleaning the salt water strainers. The water tank is below the floorboards and the tank side lay against the hull. 100% of the time has been in the tropics - maybe not as efficient as air cooled but it’s what we have.

Chuck
Jacaranda

You remind me of my brother years ago when he bought his first Porsche, he asked me why more cars weren't air cooled. I thought for a minute and told him they are all air cooled, he of course said no they are not, they have radiators, to which I asked what cools the radiator?

If your tank is not against the hull, maybe it is water cooled

water cooling can be argued to be more efficient than air cooling, just usually it brings more problems with pumps hoses, leaks etc. and is often more trouble that it's worth. Ground source heat pumps for a house are more efficient, but they are way more trouble prone and so you don't often see them anymore

[OzePete]

Originally Posted by Mike OReilly

Thanks Richard, this is very kind of you. Sorry for the delayed response, but my net access is sketchy, and I wanted to be able to respond fully. I’ll respond in the body of your message.

Wow Mike you must have nearly had a heart attack when you saw that 176A/H per day figure!

I think the poster who quoted the 176 A/H figure assumed you wanted to refrigerate both cabinets but even then the figure is extremely high or he was quoting some very inefficient systems.

To refrigerate your main cabinet to operate as a refrigerator (+2 to +4C) in the Bahamas you will consume *36 Amp hours per day, and operating the same cabinet as a freezer you will consume *61.1 A/H per day. This is your worst case scenario.

The *consumption figures I have quoted are what can be expected using an Ozefridge AW480 air and fresh water cooled condensing unit coupled to twin P53-35-5 eutectic plates.
This package benefits from the superior efficiency an air cooled, water assisted condensing unit provides, and the greater COP of a eutectic system.

The data here is related to your main cabinet. Fridge outcomes are blue, freezer outcomes are green.

Click on chart to expand...



From the chart you can see that in your worst case situation operating in the (37C) Bahamas as a freezer, the duty cycle is still less than 40% therefore you could allow spill over into the adjacent cabinet.

Also note the bottom panel indicates that operating as a fridge in the Bahamas this system only requires 1.5 run cycles per day. (That's correct, one and a half cycles per 24 hours!)
The builtin ECO2 power management will cause at least one run cycle when power from your solar etc is abundant thus reducing battery demand / capacity considerably.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[Mike OReilly]

Originally Posted by Richard Kollmann

...If you could improve the 12 volt power grid on boat with 800 amp-hr capacity then there is more than one available icebox conversion unit available with a choice of standard evaporators. Freezer evaporator need to surround boxes content as much as possible.
For the refrigerator box I recommend a bin shaped multi purpose evaporator.
Companies that offer the Danfoss BD50 system and several evaporato are; Adler Barbour, Seafrost, Cold Eh, Isotherm., Frigoboat and Nova Kool .

If the energy demand or energy storage cannot be resolved then Technautics would be the only company I can recommend that has true holdover eutectic holding plates. It is important to understand that only when compressor is running will energy be stores in eutectic plates, this is why large power grid capacity is important.

THankyou Richard, I really appreciate the analysis. I agree my battery bank is undersized. I have plans to increase it, possibly as high as ~800 amp-hrs. It all depends on how many 6-volt batts I can squeeze into my space.

Our charging system currently consists of 400 wats solar via a MPPT controller, and a 400 watt wind gen, along with a standard sized alternator (55 amp?), and a backup portable gas generator.

I will look closely at all your suggestions. Thanks again. It’s deeply appreciated.

Originally Posted by OzePete

Wow Mike you must have nearly had a heart attack when you saw that 176A/H per day figure!

I think the poster who quoted the 176 A/H figure assumed you wanted to refrigerate both cabinets but even then the figure is extremely high or he was quoting some very inefficient systems.

To refrigerate your main cabinet to operate as a refrigerator (+2 to +4C) in the Bahamas you will consume *36 Amp hours per day, and operating the same cabinet as a freezer you will consume *61.1 A/H per day. This is your worst case scenario.

Thanks Pete, I don’t want to start anything here, but the numbers are large. You are correct in saying I don’t need to refrigerate both cabinets. The spill-over “refrigerator” is really just a cool box. I wasn’t very clear with this — sorry.

I really appreciate you taking the time to crunch my numbers. And will spend some time to understand your chart and recommendation. They are very much appreciated.

I’ll likely have more questions for both of you as I move on with this project. Again, many thanks.

[Richard Kollmann]

Originally Posted by Mike OReilly

THankyou Richard, I really appreciate the analysis. I agree my battery bank is undersized. I have plans to increase it, possibly as high as ~800 amp-hrs. It all depends on how many 6-volt batts I can squeeze into my space.

Our charging system currently consists of 400 wats solar via a MPPT controller, and a 400 watt wind gen, along with a standard sized alternator (55 amp?), and a backup portable gas generator.

I will look closely at all your suggestions. Thanks again. It’s deeply appreciated.



To refrigerate your main cabinet to operate as a refrigerator (+2 to +4C) in the Bahamas you will consume *36 Amp hours per day, and operating the same cabinet as a freezer you will consume *61.1 A/H per day. This is your worst case scenario.

Thanks Pete, I don’t want to start anything here, but the numbers are large. You are correct in saying I don’t need to refrigerate both cabinets. The spill-over “refrigerator” is really just a cool box. I wasn’t very clear with this — sorry.

I really appreciate you taking the time to crunch my numbers. And will spend some time to understand your chart and recommendation. They are very much appreciated.

I’ll likely have more questions for both of you as I move on with this project. Again, many thanks.

Mike you may want to check for opinions from experienced Blue Water sailors who experience your planed trip south each winter. The Seven Seas Cruising Associations Forum with their six hundred active members may be able to help you separate the spin from actual fact. Remember worst case is a only a safety engineering tern. In your case old insulation at maybe less than R 20 plus battery storage capacity should be your main concern. When you can not improve insulation you increase refrigeration capacity.

Hopefully followers on this forum will also help you sort out the grain from the chafe.

[a64pilot]

I can tell you from my experience that if you have some excess cooling capacity, everybody is happy, temps recover quickly when you add in a large heat load like a lot of warm food to Cool or freeze etc.
If you have little excess capacity it takes all day long for the fridge to recover from having a large watermelon placed in it, and you learn to not put the watermelon in and a case of beer or Cola, large container of ice tea whatever.
Secondly, nothing ever seems to work as well as the numbers say it should, and the calculated results are only as good as the inputted data of which there are unknowns, like insulation.

[Richard Kollmann]

Originally Posted by a64pilot

I can tell you from my experience that if you have some excess cooling capacity, everybody is happy, temps recover quickly when you add in a large heat load like a lot of warm food to Cool or freeze etc.
If you have little excess capacity it takes all day long for the fridge to recover from having a large watermelon placed in it, and you learn to not put the watermelon in and a case of beer or Cola, large container of ice tea whatever.
Secondly, nothing ever seems to work as well as the numbers say it should, and the calculated results are only as good as the inputted data of which there are unknowns, like insulation.

a64Pilot, You are correct there is a difference between a salesman’s market projections from charts and the real world conditions. The base line chart I use is always designed for tropical weather conditions 90 degrees F ambient air and 89 degrees F seawater temperature. Other factors include Total realistic insulation R value, Two people on board, Cubic inches of area to be refrigerated, What temperature does owner desire inside refrigerated area. With this information I can formulate as abstract philosophy to explain which can only be proven by past experience.

Once a boat owner has the worst case amp-hour projection they can easily project down to the conditions surrounding the boat’s present operating location by ; Subtracting present ambient temperatures from my worst case tropical condition temperatures. If this figure turns out to be 25 degrees F difference then energy consumed and Btu consumed can be cut in half.

Why are my tropical projections higher than a sales person’s? It is because the trade school charts do not include that a refrigerator is used frequently every day in tropical climates. Each person onboard increases the boxes heat load by 1000 btu per day.
Also included in my worst case projection is freezing two pounds of ice cubes per day. If you do not want two pounds of ice cubes per day he can delete 5 amp-hrs per day from my projections.

I have no affiliations other than information exchanges with the icebox refrigeration conversion companies. I receive emails every day with thanks for my help I can not remember ever receiving the insults as I have received lately.

[hzcruiser]

Originally Posted by Richard Kollmann

[...]
I receive emails every day with thanks for my help I can not remember ever receiving the insults as I have received lately.

Here in this thread on CF? I must've missed them.

[Nanamuk]

I love my Nova Kool - first one lasted 20 years and was probably repairable due to a leak in a valve but I put in a new unit with a freezer compartment rather than just a cold plate. Here in the PNW I am on a mooring and live on 2 85watt 1992 vintage solar panels and have more trouble with freezing the lettuce than running my 20 year old Trojan 105's down. Nova Kool has several DIY options to retrofit an old fridge/ice box and being in Canadian $'s will be an advantage. The guy who answers the phone will probably be the guy who runs the place so you get great support and advice!