Design your own efficient Ice Box Conversion Refrigeration

[poiu]

Originally Posted by ColdEh Marine

Hi Poiu.

Do you have a link to those fridges. I do remember having a look at something like what you are talking about but can't recall the manufacturer.

Regards John

Here's a big one:
https://home.liebherr.com/en/gbr/pro...ls/k-4310.html

78Kwh per annum consumption. That's 0.74 amps average current draw at 12v or 18 amp hours per day. I suppose a bit more in hot climates, but still it's incredible and for such a huge fridge too.

[Richard Kollmann]

Groundtackle Question
Richard, I'd like to ask about this comment of yours;
"Refrigeration performance on sailboats is affected more by seawater temperatures than power boats."

Sailboats are displacement hull boats where most have converted iceboxes partly below the water line. Sailboats also have less air circulation below deck. The majority of boat refrigeration designs I did were for boats planning on cruising in tropical waters where seawater temperature is warm 24 hours a day even though nighttime air is cooler.


John Question about your insulation formula
Answer, My first two books provided calculation on box size and heat conduction of polyurethane insulation. After consulting with a marine insulation company I added the requirement of encapsulating insulation in builders plastic. I then added Extruded polystyrene (Blue board) insulation if insulation was to be put inside an already built box. To test insulation on many boats I sent a data logger to be put in each live aboard boat for 14 days. The graphic computer displays of box temperature and compressor activity would pinpoint a problem if there was one.

John I have no magical formula except to say I prefer at least moisture free insulation with an R value of 20. If design conditions indicate R20 is not enough and total rebuild of box is not desirable I increase refrigerator compressor capacity. Watch my slide Show on how I select Boat refrigeration.


Poiu Question Low energy Home refrigerators
Answer, There are many ways to creatively address the refrigerator energy question and some even compromise a unit's reliability. It the refrigerator has an energy saver function you control make sure you understand how it alters the normal function especially if it is a two door with a roll out freezer.
I bought a new $2500 refrigerator when I moved to the island and for the first time I paid for a two year extended warrantee. Twenty three months and three ice makers and four design defects corrected I seem to have ice.

As to why new home refrigerator insulation is thinner and better than before it will be because of improved insulation.

[Typhoon]

Originally Posted by poiu

Here's a big one:
https://home.liebherr.com/en/gbr/pro...ls/k-4310.html

78Kwh per annum consumption. That's 0.74 amps average current draw at 12v or 18 amp hours per day. I suppose a bit more in hot climates, but still it's incredible and for such a huge fridge too.

18 amp hrs is great for a fridge that size , the only issue I have with there testing is that the ambient temperature is not stated during the test period. There info sheet says the the device is designed to work in a 10 to 32 C environment . Failing to supply the ambient temperatures of the test makes the test worthless . I dislike tests that don't state all of the parameters. They can be misleading .

I will drop them an email and see if I can get that information.

Regards John.

[toddedger]

Richard I really wish your books were in ebook format. Would love to have on my kindle. I don't have room for a lot of books on board. Ebooks or pdf doc. Is the way of the future. Plus I see your E-commerce site is down. I'd like to buy one of your books but I'm out of the country and not sure if it will catch up to me as I move along. Sending a check by snail mail takes a long time. Please consider using an electronic publisher.

[poiu]

Originally Posted by ColdEh Marine

18 amp hrs is great for a fridge that size , the only issue I have with there testing is that the ambient temperature is not stated during the test period. There info sheet says the the device is designed to work in a 10 to 32 C environment . Failing to supply the ambient temperatures of the test makes the test worthless . I dislike tests that don't state all of the parameters. They can be misleading .

I will drop them an email and see if I can get that information.

Regards John.

It's going to be a test defined by the EU. All appliances have to have energy labeling in the EU. This one has the highest rating. I could look it up, but it's going to be 22 deg C I expect. In a way it doesn't matter to consumers as the relative performance is what counts and the best are maybe 3 times better than the worst.

[Typhoon]

Originally Posted by poiu

It's going to be a test defined by the EU. All appliances have to have energy labeling in the EU. This one has the highest rating. I could look it up, but it's going to be 22 deg C I expect. In a way it doesn't matter to consumers as the relative performance is what counts and the best are maybe 3 times better than the worst.

Thanks for that , I agree. I wonder what they call refrigeration temperatures. We use 1C to 3C , cooler then most . Sometimes I put in down to 0 to 2C in the summer when I want the beer really cold

Im not sure a fridge like this would work on a monohull , maybe work well on a power boat or a catamaran .

Regards John.

[poiu]

Originally Posted by ColdEh Marine

Thanks for that , I agree. I wonder what they call refrigeration temperatures. We use 1C to 3C , cooler then most . Sometimes I put in down to 0 to 2C in the summer when I want the beer really cold

Im not sure a fridge like this would work on a monohull , maybe work well on a power boat or a catamaran .

Regards John.

I'm sure a search can find the test parameters. I would expect 3 to 4 deg C.

That fridge would be a bit big for most boats and would need bolting down well. There are plenty of smaller ones on the market. It was more of an example of how very efficient domestic units can be.

I don't believe it is the insulation as suggested by Richard. They are thinner than most marine installations, so even with a better material are unlikely to be better insulated. I expect the COP is better. The standard for a Danfos compressor is not that good at 1.2 about. Air con units can go to a COP of 4 to 5 and maybe there are fridge units around that good too. It may also be helped a bit by a higher gas temperature, which should be easier to achieve with a huge evaporator such as they seem to have.

[john61ct]

Or maybe pricey enough (green premium) that they use the newer fancy-tech/pricey high R-value per cm insulation?

[Taswildlife]

Thanks Richard
I am in the process of doing a fairly major re-fit on my boat and the refrigeration system is to be part of this. I was already intending to remove my old house size 3 way gas, ac dc fridge. I intend to install +1000 watts of solar panels and build my own ice box in. I knew I had to get my head around all the information that you have presented so clearly in your post. Thank you, you have given me what I will need as a reference as I begin to select my components and where to situate them

[Hoodsail]

Richard, thanks for the extensive post on the elements of boat refrigeration. Have had your site bookmarked for awhile. Re-insulating my 1978 icebox is on the "to do" list, as a first step, to decide whether refrigeration is something I want to add. Off shore for limited time, 5-6 days, so experimenting with different uses of "blue ice" to cool food. Next yr or 2 may make the refrigeration leap, if re-insulating doesn't get me a week or so..

[Richard Kollmann]

If you want dependable efficient refrigeration stick to the basics avoiding the faddish expensive marketing gadgets. It takes around 100 watts per cubic foot of refrigerated box to maintain 40 degrees F box temperature in a warm climate. When alternative energy is available solar or wind You might consider large eutectic energy storing holdover plate evaporators. When planing for solar panels check the sun weather day charts for where you plan to cruise.

Danfoss does offer design concepts and hardware for solar voltage from 10 to 45 volts.

[OzePete]

Originally Posted by ColdEh Marine

Thanks for that , I agree. I wonder what they call refrigeration temperatures. We use 1C to 3C , cooler then most . Sometimes I put in down to 0 to 2C in the summer when I want the beer really cold

Im not sure a fridge like this would work on a monohull , maybe work well on a power boat or a catamaran .

Regards John.

Exactly John. Lots of claims but not the factors to indicate performance in the real world. Without cabinet and the operating environment temperatures, outcomes claimed mean very little.
Given the fact that compressors at a given capacity / RPM produce near identical results in every respect, the issue of efficiency comes down to three main factors:

1: Cabinet insulation. There are some very interesting products being used by cabinet manufactures specially in the EU and Asia so would not be surprised if they are getting some great R factors.

2: Evaporators. This is the device that collects heat from the cabinet and has a big bearing on power efficiency. Different evaporator types cause vastly different efficiency factors. The one depicted being a cross finned forced air type, refrigerates at a high evaporating temperature (like a eutectic plate does) and therefore a very high COP factor. (COP is a figure indicating the watts of heat removed per watt of electrical energy consumed, like MPG, so the higher the figure the greater the efficiency) This system depicted is likely to be running a COP of about 2.0 which is very good when you consider a cyclic aluminium plate has a COP usually less than 1.2 !
3: Condenser. It is not practical to quote a system to operate only within a maximum environment of +32C for marine use.
The condenser is responsible for disposing of the heat gathered from inside the cabinet.
As the ambient gets hotter not only does the heat load on the cabinet increase but the condensers ability is greatly reduced and compressor efficiency is lost as high side pressures and power consumption increases. Efficient disposal of this heat specially within controlled parameters is essential for marine use.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[Richard Kollmann]

Hoodsail I have your answer. I attended in July several times the Bahamas sailboat races. There were boats crossing the 90 miles without refrigeration who were able to cool and preserve food for a week using Dry Ice. Fresh water is hauled into Bahama out islands by boat or produced by desalination. Even rain water sells at $.25 a gallon, Bahama Ice in small chips is expensive and melts fast. In south Florida supermarkets and even Walmart sell dry ice. It takes much less space than ice and when wrapped in new paper or bubble wrap box temperature and phase change time can be controlled.

Google Dry Ice to find local store, then test it instead of Blue Ice.

[Hoodsail]

Richard, good morning:
Thanks for the dry ice idea...excellent suggestion...will give it a go this season and let folks know how it works.

[woodenboats]

Please be aware that 1cubic foot of dry ice will evaporate into more than 700 cubic feet of carbon dioxide gas, which is heavier than air...