making a fridge

[ChattingLil]

does anyone have step by step instructions on how to build a fridge? I've now identified a space for one but really don't know where to start. I've searched internet and on here and found the threads about the self build kits and insulation, but I don't know anything about ventilation required, or whether the location I've found is good for it, or what else I need to do.

 

[William_H]

Fridge

the most common fridge kit for a medium sized boat typically has an evaporator which is the part that gets cold that fits into an insulated box. This is connected to a compressor and condenser that can be remote by a few feet. thi sis the part that gets hot and needs ventilation. Typically this might be in a locker or cupboard and should have ventilation in at the bottom and out at the top. A small computoer type fan can be useful here. The two parts are connected by a connector system which does not lose gas when the two pipes are connected.
The box in its simplest form has thick foam insulation preferably 40 or 50 mm thick with a lid opening at the top. Front opening loses more cold when opened but is sometimes used. You will need holes later sealed for the two gas pipes and also a hole for the thermostat or wiring.
More complex fridges will have an area with the evaporator fitted which runs as a freezer with a separate area partially sealed off for warmer temperature fridge.

The compressor and evaporator tend to be rated by fridge size so more powerful for larger fridge. A small well insulated fridge might draw 5 to 8 amps at 12v and run 20 0r 30% of the time depending on ambient temp and amount cooling needed. So battery systems and power generation becomes a concern in sailing boats.
You can go simpler with a complete fridge like WAECO Cf 25 which I use in the car. This will run happily as a freezer. However insulation is not brilliant so current drain is more. Engel make a sweet little front opening fridge which looks just like a small kitchen fridge, or you can go an engine driven compressor (air conditioner style) water cooled evaporator and huge freezer like fishermen use for freezing catch. Real freezing power. good luck olewill

 

[pcatterall]

Comprehensive as ever. Thanks Olewill as I am considering same.

 

[rogerthebodger]

Do not skimp on the foam insulation. My first fridge was 50 mm thk, my next ine I made 150mm poly urethane which reduced the duty cycle (on/off time) to 15/20%.

The main problem I have is condensation on the stainless steel inner case and door in the humidity of the Durban summer.

 

[MoodySabre]

Lisa - you don't say if you are starting completely from scratch or have a cool box that you want to turn into a fridge. I put a Waeco kit into my cool box - a fiddly but very worthwhile job. If you a cool box then Penguin have some useful info.

If starting from scratch then finding a box to insulate with a tight fitting lid would be your main challenge.

Several days without being plugged in (with a batt charger running) or running the engine will take its toll if you have just one domestic battery. I wired the fridge in so that it cannot run off the starter battery. This year I added another domestic battery as a low battery was an issue on an extended trip last year. I tend to run the thermostat higher hwen plugged in or motoring and turn it down when under sail or moored without leccky.

I have a 12v cool box if you want to borrow one for a trip (never usd still in wrapper).

 

[ChattingLil]

Thanks Olewill and thanks Roger.

I have a 12v coolbox which i've been using for the past couple of years, but since i've had the opporutnity to actually spend more time on board I've reorganised the boat and found a good spot to put the coolbox. It then occured to me that the same space could be insulated thickly and converted to a fridge space. I'm fairly sure I could make the box and appropirate lid, but it was all the actual working gubbings that I'm not sure of!

I am starting from scratch and have a hole about 90x60x40 to play with. It's right next to my fuse box and electrics cubboard and i'd have access underneath it too.

No urgency - can't afford it yet (am saving up for a new tiller pilot) but I'd like to get it on my list of things to do and save up for.

 

[Searush]

Make yourself a Sock Powered Fridge

Look, what you really need is a "Sock powered fridge". Let me explain.

Part fill a bowl or bucket with sea water, there should be plenty quite near. If you have an old wooden boat there may even be plenty inside. Place the food to be kept cool in the sea water, you may wish to use a waterproof container for some foods, milk should be OK in it's carton or bottle. Next find an old sock, vest, towel or even an old rag from the tool kit. Cotton is best, but man-made fibres will do - wool is too loose a fabric & will not work. Place the cloth in the sea water & soak it, then spread it out around the rim of the bucket so that about 1/3 is still in the water.

What happens next is quite amazing, the sea water in the cloth evaporates, but more water is drawn up by capilliary action (that's why wool won't do). The evaporation cools the cloth & the bucket. OK, so it won't produce ice cubes, but it will keep food cool & is totally eco-friendly & has been used for millenia by native people in hot climes. In some countries special porous pots are used to produce the evaporation, but it isn't essential.

 

[sighmoon]

Look, what you really need is a "Sock powered fridge". Let me explain...

How many degrees does it cool by? I tried looking up some info online, but failed.

Then I thought laterally and thought I'd compare average sea temperatures, with average land recorded temperatures:
Average sea temperature: 11C
Average land temperature: 11C
GOt the data from a quick google, so sources may be dodgy, but seems kind of reasonable: sea is cooler in summer, land is cooler in winter.

OK, maybe the cooling effect is lost to rounding errors, but it may still not qualify as a fridge.

My assumptions may not be valid either - the land isn't totally arid for instance.

 

[pappaecho]

I built a fridge 5 years ago and cheated heavily. The 1979 boat has a "cool box" space which did not remotely fit any size pf modern fridge on the market....
However a friend took me to a Caravan dismantler and low and behold we came up with an old, but good condition Electrolux caravan fridge, which fitted exactly the space.

The evapourator system was based on ammonia and was u/s. Removed the entire cooling system, replacing it with a modern Waeco kit. The advantages are that the fridge carcass was in very good condition and the fittings of the new compressor took only a couple of hours, and since was have enjoyed many ice cold G&Ts etc. This system uses less amps than a Peltier solid state fridge system which was about half the volume, and did not fit in the space properly

 

[rogerthebodger]

The way Searush sock fridge works is by the fact that it takes heat to evaporate the water which causes the temperature of the container to get cooler.

The old type absorption type fridges works that way.

OK in cool low humidity places like the UK but not in warmer places like the med.

I had that type Durban, OK in winter but could not cope in summer.

 

[William_H]

Evaporative cooling

Here in West Oz the evaporative airconditioner is very popular. This because we usually have very dry hot summers. A big box sits on the roof with straw type medium on all 4 walls. Water is pumped up so it flows down through the medium. A large fan then draws air in through the medium and it is distributed around the house. It works well on dry days. However we get some hot humid days when it just won't work. Many people have a small refrigerated aircon in one or more rooms just for those days.

Re boat fridges. What is surprising here is that fridges are not that common. Indeed I have friend who has one but does not use it. This may be because there are no good places to voyage over long periods. So the weekend voyage is the most common. Here a good cool box and a big lump of ice or bottles of frozen water are very adequate. It saves all the worry about battery power and charging. Maybe you want and need a fridge but you should build the cool box and try ice first. It is all a question of if you stay away long than 4 days can you get more ice? Ice is actually available widely here at about 2squid for a large block.
good luck olewill

 

[mitiempo]

Here`s a link that might help. http://www.kollmann-marine.com/

 

[Pasarell]

Fridge

I built a fridge in my Moody 33 last year using a Waeco kit.
Most 33's I've seen have put a ready made fridge under the galley sink but I didn't want front opening partly for energy loss and partly in case contents tip out when heeled. I have 6 large lockers under the saloon seating so used 2 of those, one for the fridge and one for the compressor. All the lockers have the hull as the bottomThe fridge locker I lined with 50mm of foam, Celotex I think it is called. Then made a liner from water resistant ply. The liner had to be in several pieces to fit through the existing locker top opening which I didn't want to change. Once the liner was fitted sealed all the joints and painted with white acrylic. The Waeco kits come with the evaporator plate and about 2m of tube to the compressor which you only connect together when everything is ready. Fitted the evaporator plate and made a hole for the gas tube and temperature sensor to the next locker where the compressor would be. Next fitted a small platform in the adjacent locker for the compressor to be attached to and routed the power cable with oversized wire to avoid voltage drop. Finally connected the gas tube to the compressor which is the most worrying part. It all comes sealed and pre-gassed. You only have 1 go at connecting the 2 parts but it is actually very easy and difficult to get wrong!
The locker I used started off at about 120L but with insulation and lining ended at 65L which I find plenty big enough. I live aboard the boat when in the UK so the fridge gets plenty of use. When about half full and the thermostat set to 1 (out of 7) last summer the fridge stayed at about 3C and ran for about 40 seconds every 5 or 6 minutes. Current draw is 3.5A IIRC when running.
Both fridge and compressor lockers are partly below the waterline so naturally cooled but I was worried about the compressor overheating in a confined space so planned to cut holes into the saloon and fit a computer cooling fan at the top to force air out. In fact that hasn't been necessary as the compressor runs so little. Still an option for when I head south in a year or so.
Power consumption was an initial concern. I have 2 x 110A domestic batteries with a Rutland 913 wind generator and shore power for when necessary. In practice the generator provides most of my power but I used about £20 of shore power during the winter when I was there most of the time, covering fridge, lighting, heating, TV etc.

 

[iidesu]

Wow~~wonderful, I didn't know that before.

 

[pcatterall]

How many degrees does it cool by? I tried looking up some info online, but failed.

The latent heat of evaporation of water is 40 cals per gram (AFAIRecal!!)
if you can use the sock idea in the shade but in a breeze this system is very good especially in low humidity areas. A canvas bag using sea water and with cans or bottles of beer inside becomes quite acceptably cool.

 

[maxi77]

How many degrees does it cool by? I tried looking up some info online, but failed.

The latent heat of evaporation of water is 40 cals per gram (AFAIRecal!!)
if you can use the sock idea in the shade but in a breeze this system is very good especially in low humidity areas. A canvas bag using sea water and with cans or bottles of beer inside becomes quite acceptably cool.

Indeed, as a very young midshipman I had to spend time in the engineroom (operating the throttles with 20000 shp at your control was pretty good) and boiler rooms and we kept our limers cool in a glass demijon with a canvas coat, just keep the coat wet and the limers were kept cool. Steam drains also were very good for heating up the middle watch tinned stew, or brewing kye.

 

[mcframe]

Look, what you really need is a "Sock powered fridge". Let me explain.

That sounds a bit like "Wrap Chablis bottle in thick towel secured by fine line, practice jug sling knot, dunk in sea and hoist from signal halyard for 2 hours until dry and well chilled" ;->

Making a fridge: I bashed out old coolbox (keeping worktop lid), lined extended area with 40mm B&Q insulation & filled gaps with PU foam and got local GF bloke to flow-coat inside it before fitting evaporator & compressor. Seems to work well, 'tho I sometimes carry a small Igloo coolbox to keep things cool in the car on the way down and take stuff to the beach.

 

[sighmoon]

How many degrees does it cool by? I tried looking up some info online, but failed.

The latent heat of evaporation of water is 40 cals per gram (AFAIRecal!!)
if you can use the sock idea in the shade but in a breeze this system is very good especially in low humidity areas. A canvas bag using sea water and with cans or bottles of beer inside becomes quite acceptably cool.

Alright for keeping milk?