Stainless steel & fridges

[gunnarsilins]

As I´m in the process of rebulding the fridge to a custom made box opening on top I´m considering to use stainless steel for the "inner liner".
Can anybody of you see any drawbacks?

 

[ccscott49]

No drawbacks atall, as long as you have somebody to make it for you, Don't forget the drain, you could even have a little spigot put on, with 1/4 BSP threads and put a little tap on it for the drain. THere are marine and domestic fridges around, with stainless inside, so it would be fine.

 

[heerenleed]

The first thing that springs to my mind is this English expression some friend taught me: stainless steel isn't.
But honestly, I think of another nuisance: if you line your fridge with anything steel or alike, it will always be wet by condensation. On our boat, we used to have a wrong system installed in our fridge, the compressor was ok (untill it died) but the evaporator was huge. It never got quite cold enough (to freeze the condensation on it) so we had a wet fridge untill we replaced the system. We now have a small evaporator which has some ice on it instead of condensation streaming off.

A SS lining will be cold enough for condensation to form, but too warm to freeze it. I would use any kind of plastic lining. Even epoxied wood.

Good luck

Peter a/b SV Heerenleed, Steenbergen, Netherlands

 

[steve_cronin]

Two problems.

Problem 1

First the weight of a SS liner will compress the insulation thereby making it less efficient on the bottom and tend to pull it away therby leaving gaps on the top. The whole heavy lump will move around and within a few months you will have a loose liner, clunking noises, powdered insulation everywhere and an inefficient fridge running your batteries down all the time.

Problem 2

To vercome the movement in "Problem 1" above you will need some sort of rigid fixing between the inner liner and outer casing. Trouble is, the moment you fix a screw or series of screws or studs between the inner and outer you have immediately breached the thermal barrier of the insulation and defeated the whole object of the fridge. Boat fridges need to be efficient because we can't afford the power consumption of domestic units which just won't cope with the < or = 60watts we have available at best. (Unless we are talking big motor yacht of course).

Then as to the "drain" there's another breach of the thermal break. My last boat had such a drain because the box was originally intended to be an icebox. When we converted it to a fridge this was sealed and insulated over. Mopping out isn't a problem and we keep the ice cubes in a large screw container. The current Bavaria has no drain because they built a fridge to be a FRIDGE.

No to my mind, SS is not an appropriate material for a low energy marine fridge liner (unless you can get it made wafer thin and then it will be prone to easy damage)

 

[ccscott49]

I think thats the secret, very thin stainless sheet is also very strong, especially when made into a box, the weight I doubt will compress the insulation, does the plastic liner, when the fridge is full? No it doesn't. A lot bigger boats have custom built fridges, they are very commonly made of stainless. I guess it also depends what you use for insulation, a custom plastic liner is going to be expensive and difficult to find, you can get a welder/fabricator to knock you up a stainless liner pretty cheaply. IMHO of course, Thats the way I would go if I was building one in. It was also very common in older boats, with built in fridges, to have galvanised steel lioners, which were a bit heavier than stainless, plastic liners came in for mass production cheapness. all again IMHO.

 

[SteveA]

I think that stainless steel would be an idea material - I would suggest contacting a company that carrys out pipework insulation as a supplier. The stainless steel sheet used by many of them is very thin, strong and does not rust! - the company I work for uses acres of the stuff!

 

[pvb]

Sounds attractive

Only drawback with stainless steel might be the need to have relatively angular corners. Fridge with GRP liners tend to have nicely-radiussed corners which make it easier to clean them.

I personally dislike drains in boat fridges - I don't think it's a good idea to let food-related spills drain into the bilges.

Rebuilding your fridge is a good opportunity to improve the insulation. I've used building-grade foam sheeting to add to the existing insulation, and it seems worthwhile.

Another way of increasing the efficiency of a boat fridge is to enhance the ventilation over the condenser coil, which is often tucked away in a locker with poor ventilation. I used a 12volt computer fan to get more airflow; it's wired so that it only runs when the compressor is running, and it's virtually silent and draws very little current.

Had you thought of building a small red light into the inside of your fridge? Although it sounds a bit pervy, it helps to find stuff at night without ruining night vision. The new LED lights are ideal.

 

[hutch]

Stainless steel is - as long as it's 316! 308 will rust in a marine environment.

 

[VMALLOWS]

Re: Sounds attractive

Totaly agree with the extra fans. Even with a stand-alone absorbtion (gas/electric) fridge it makes a tremendous difference in hot weather. I use one of the small
3 inch square ones. In fact a 24v version (simply because I had several) running at 12v. It is still quite adequate, silent, and uses next to no power.

 

[oldsaltoz]

G’day Gunnar,
I would think 316 stainless is perfect; the comments above look good too. However, I would add that you should avoid taking the top of the steel liner out to the edge; it looks great but loses a lot of your cooling. Also, if the lid is large, consider putting a smaller lid in it; we had one like the old fashioned ice cream vendors had with the tapered edge, stops all the cold air being blown out when you lift a large lid. I like (pvb’s) idea of a red light inside, must investigate this further as it beats fumbling around till your hands are frozen.
Running a fan inside the freezer will also improve its performance for very little power draw.
Hope this helps…

Andavagoodweekend Old Salt Oz……/forums/images/icons/cool.gif

 

[ccscott49]

Re: Sounds attractive

Where did you get the 24v ones? just what I need for my inverter, fridges and freezer, do they make a mains ac one aswell?

 

[gunnarsilins]

Decision made!

I´ll go for stainless steel.

I don´t believe the steel will crush the insulation by its own weight.
A thin welded SS box, covered with thick, glued builder grade foam insulation and finally a glued and screwed sturdy plywood box on the outside will make a strong sandwich construction.
It´s hard to beleive that the SS box will have a chance to move even a slightest bit.

With a drain in bottom, with an access for a container, so no spillage can go into the bilges, will probably do the nuisance with condensation bareable.

The sharp corners will be less easy to keep clean. But a brute cleaning action now and then should be enough, especially with an drain.

Regarding additional fans, yes that is a good idea, but I´ll go for a compressor with an external keel cooler. (See another posting about a week ago)

Thank you all for taking your time and contribute with lots of good and interesting thoughts!

 

[vyv_cox]

Re: Decision made!

I've come to this discussion late, been away for a couple of weeks. My son runs a business building A/C and refrigeration equipment. He regularly uses stainless steel for the inner skin. It's relatively cheap to fabricate and works perfectly well. For bigger installations he uses Tek-tanks, they will custom build liners with doors wherever you want, e.g. a combined refrigerator and cool box with one top lid and one side door. Stainless gives easier options for shelf supports.

Drains can be a nuisance, especially if milk is spilled! But a container to catch spillages should solve this one.

Incidentally, 316 SS will tarnish just as readily as 304, its pitting resistance is improved by the addition of 2% molybdenum but that's all. If you are welding the box it may be better to go for a 304L or 316L (L for low carbon) Not strictly necessary but it will be a better job.

I'm just about to uprate my refrigeration in preparation for warmer climes. My son is designing me a water-cooled compressor with two holding plates, one for the cool box and one for the biggest refrigerator I can fit in the space available. By some clever piping he can arrange that they are switchable, giving me options for either box. I assume you will use a holding plate? Very efficient, saves lots of amps!

 

[ccscott49]

Re: Decision made!

Can you give me a contact for your son, please?