refridgeration

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songlinebvi

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Hi all, I,m living on a Northney 34 in the British Virgin Islands. I realize I do not need heat. i have NO inboard deisel, nor a generator. Can anyone give me a clue to a fridge/freezer. I am running an ampair100, and a 1000 watt solar panel into four li9fe-line 120 amp/hr batteries. I have removed the 3-burner stove/oven, and would like to put a fridge unit in that space. It needs to be an efficient unit. Any input would be appreciated.

Thanks, Scot
 
The key to an efficient fridge unit is insulation. The more the better. If you do a search here you will find Timevans2000 with a fridge using 100mm thicj insulation and using the result as a fridge , or fridge/freezer, or just as a freezer at abt 2 amps/hr with a danfoss compressor and a keel cooler.

suggest you look at http://www.penguinfrigo.co.uk/specify/default.asp and then talk to them.

Any system running at minimal amps will not be cheap.

Alternative is one of the new Waeco coolboxes fitted with the danfoss compressor - again they are not cheap, and they will use more power than a really well insulated home build.
 
Hi Scott,

I think you may be a little optimistic. javascript:void(0)
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I am no refrigeration expert, but have installed 3 refrigeration units over the years and understand electricity to a degree. Waeco do a number of compressors and cooler units that can be mixed and matched to suit the application. They, or their catalogue which is quite informative (maybe also the web site) are very helpful.

Whatever spec you come up with you need a very well insulated enclosure, top opening, with a well sealed and equally well insulated lid. The freezer on Fuga which I built is quite large (by boat standards) and was built in 6mm ply which we painted on the inside with a two part epoxy paint (Skippers Epofond A09)which is typically used for lining water tanks etc. This enclosure was insulated with 100 mm (minimum recommended) polyurethane foam all round. (It took about 14 aerosol containers). This amount of insulation leaves you with relatively little room for contents unless you have a realistic space to fill.

Fuga's freezer has a special fan assisted evaporator, and the compressor cooling is fan assisted. The compressor is in the bottom of a cockpit locker, underneath a floor, so has plenty of air and room in which to cool itself, and exchange heat with the water. The current drawn at 12v. is about 7 amps, and the duty cycle is probably about 30%. Wherever you lose your heat, in the Caribbean the water temperature is going to be a lot higher than in Europe, and therefore your power consumption will be greater.

On his Contessa 32 Jemmana, on which he went round the world, my son used a sea water cooled heat exchanger, but this had to have a pump, and it wasn't particularly reliable. He had a storage type evaporator, that took advantage of the engine when it was running, but this won't apply to you. I think the water cooled compressors are no longer available from Waeco.

So fridges and freezers are quite a power draw. A smaller unit might still take 5/6 amps when running. Say about 50 AH for arguments sake, each and every 24 hours.

Looking at your supply side, you have an Ampair 100. I assume this gives you about 5 amperes for about 6 hours a day, if you are lucky? I know you get nice breezes out there. Say 30AH a day.

I am a bit confused about your 1000 watt solar panel. I have a picture of a boat covered in solar panel! The largest you can usually sensibly accomodate on a boat are about 100W. Fuga has an array of 3 x 50W mounted across the stern, and most people think this is OTT! A 100W panel gives about 8A and again for about 8 hours a day, or 64AH, say.

So I am guessing the unit will optimistically take at least half of what you have available to throw at it.

You have a large battery bank, but this is only of value if you have a way of keeping it charged. With no engine, and no generator, this will be a challenge unless you can hook up to shore power every day or two.

I hope this helps.... contact me if I can answer any further questions.
 
I have been reading about relative efficiencey of fridge units. I believe that there is a 10 per cent gain by using a sea water heat exchanger.

A 10 % gain for seawater inside the boat is too high a risk / reward factor for me.

I settled on a newly introduced unit from WAECO, it's self contained, measures 32 cm X 25 X 25 and uses 2 computer fans to vent the hot air to the natural heat exchanger in the ocean/bilge) 12 volt /24v auto swwitched I believe.

I wanted the specs on the unit to cut the holes in the stainless liner I had welded up so that I could align the inner liner with the outer alumium box and fill 20 cm gap with blown in fire retardant polyurethane foam.

(It turns out that the fire retardant additive to the blown in foam is inexpensive and my installer who foams fishing boats, commerical freezers etc, will not use anything but this type.)

I had to buy the unit to get the sizes!

Uses 4 amps at full power and the duty cycle is expected to be 25 % with my thickness of insulation.

Cost me equivlant of $700.00 US, 400 GBP, with taxes $1000.00 Can.

There may be better units, but I very much doubt that there are any unit that are easier to fit!

This may become the retrofit standard due to, low cost, simplicity, efficency.
 
John

You are a bit behind the times with your data.
You reckon that the largest you can accomodate is 100w, well I beg to differ -
I have a 180w panel on my 9m boat!

I know of another boat that has 4 kyrocea 120 watt panels (yes 480w total), and they also have a Kiss windGen, and in case of problems a 2kw honda portable generator!!!


Now as to your data on the fridges:
older versions of Keel cooling do have an option of the pumped version which draws water in and pumps it through the compressor to provide the cooling. However, there is another option which works very well consisting of a special heat sink unit which fits on the bottom of the boat and is about the size of a ground plate for the SSB. This heat differential creates the circulation of cold water without the need for an additional pump - hence no fan, the new evaporator plates also dont need a fan plus the compressor is much more efficient, thus a major reduction in power required.
If you set up your system with the plate in one compartment and use that compartment as a freezer, it is worth using a computer fan for the air transfer in order to make the fridge section more efficient (computer fan uses milliamps)

The compressors used by waeco, isotherm and frigicool etc are all the same - danfoss of various types.
 
I used a Norcold kit to convert the coolbox on my cat 38. Was very simple to install, had all the parts necessary (no buying bits of pipe or connectors). Got it mail order during a boat US spring special. $410 complete, plus my time. Works like a dream and takes up very little space.


But my question was wondering if there are any refrigeration systems for boats that do not require any electrical power - as the original poster, I would guess, is going to be extremely limited for power with no engine. Hence my mention of the kerosene fridges we used in Africa. If there was it would eliminate any concerns over electricity consumption.
 
You can actually make a fridge that truly needs no power whatsover by inserting a pot inside another and filling the gap with wet sand then covering the top with a wet cloth, when the water evaperates it also pulls out the heat, leaving the inside container cold. It will keep food fresh for up to 3 weeks. It was invented by Mohammed Bah Abba in Northern Nigeria.

For full details see Here

Not neccessarily what you're looking for, but interesting nevertheless.
 
My fridge onboard does not use any electricity (although I have the option of running it on 12v (abt 8 amps) and 240v. It is powered by lpg and thus of no use to a half boat (except in harbour).
 
Hello John,

Is the foam you used the same stuff that is available in B&Q etc for building use? I need to increase our insulation and aerosol foam would be a lot easier to retrofit than rigid panels.

Steve
 
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