ice chest option

[Sailm8]

I use foam insulation panels that I cut in various sizes to fill in any empty space in the cooler as we use stuff up. Also plastic bags filled with packing peanuts. When we are on a short cruise and only using half the fridge, I fill it with bags of peanuts covered with a foam layer. This reduces the volume.

 

[Winkfish]

For some reason, I have this urge to modify SOMETHING on the boat ... sometimes without any really good reason..

Welcome to boat ownership, my friend!!

 

[walt]

after all this discussion (which was great, thanks!), here is what I think I would build. You might even be able to give it a nice wood finish without it weighing too much.

I think you probably would need a fan with something like this to keep some air flow between the ice and the food and I think something like the 1 watt 13 cfm computer fan in the link below would do:

http://www.digikey.com/product-detail/en/OD6025-12LB/1053-1239-ND/2621144

The fan would somehow need to be protected but still allow air flow and be high enough on the divider to stay away from the melted ice water. There would be a switch for the fan somewhere on the boat. If you just left the switch on all the time (fan running all the time), it would use about 2 amp hours per day at 12 volts.

You still have to add ice every "few days" depending on use but you also have drink ice. Not as luxury as an electric fridge but the DC power required is maybe 1/17 th (17 times smaller). My current electrical system would handle this very easy as is.

I think you could also throw drink cans or bottles in the ice area (ie, ice cold beer). Putting cans in often would use the ice faster.. but no big deal to just buy more.

 

[Winkfish]

Just a thought, though I'm no hvac expert. Cold air sinks, so would it not be better to blow the cold air into the food chest at the top?

 

[walt]

Im not sure if it matters - you certainly want the air to circulate between the two chambers so maybe there is some way to do that best like you suggested???

Putting the fan at the top and the vent at the bottom would likely make it easier to protect the fan and keep food and ice from blocking the air flow when the lids were closed.

 

[walt]

along the idea of what Winkfish suggested..

If you have access to a hot room and a cold room and open a door between them, a fairly strong natural air current develops with the hot air going from the hot room to the cold room at the top of the door and the cold air goes from the cold room to the hot room at the bottom of the door. Try this sometime with the smoke of an insense stick and you can see the flow.

Anyhow, maybe it makes sense to have the air flow from the fan pushing air the same way the natural circulation would set up - rather than have the fan fight the natural circulation.

Another rev just for the heck of it..

 

[Winkfish]

That Makes sense, Walt. Like I said, I'm not an hvac person.

 

[Doc_holiday]

I'm not sure a fan would offer any advantage. Heat likes to find equilibrium side to side. There may be some temperature variation up and down which is why proper ice boxes have the door on top. The fan will make btu's all though few, more than no fan.

Remember to make sure you trap the drain. Cold air will rush out through a bottom drain. The ice changing state from a solid to a liquid is the point at which most of the work occurs and requires the most heat to do so.

Keeping residual heat out through good Insulation, seals etc will be most effective. Don't open the box and stare like the people at the grocery store do. If you want to add addition insulation outside that may help.

Oh a cooler from Wally World is not an ice chest. Go buy one and cut it open. The cost reduction was by removing the insulation. All they care is that it has the igloo brand and can buy and sell it cheaper than others.

 

[chp]

I tried the fridge idea when I first had my Mac. I quickly learned the hassle of power management. I build my own solar panels, so I built 2 30 watt. Installed 2 group 27 batteries and made an arch to put the panels on. I spent more time monitoring the power use then doing anything else. One bad day of no sun and I was behind and couldn't catch up. The fridge died which was probably the best thing.
I picked up 2 coleman extreme coolers. I added a piece of blue styrofoam to lay over the top of the food and ice to keep the cold from escaping through the lid. After a 7 day trip we only got ice once.
We use lock and seal containers to keep the water out of the food and vacuum seal machine for the meat. We also freeze bottles of water. Had to actually take them out to thaw. They were still frozen at the end of 7 days.
One thing I did like about the fridge was the front loading.

 

[walt]

Im temped to cut up a "five day" ice chest to see whats inside.. but I also bet its got almost no insulation. Its good that you can still do anything you want to your boat that meets the tradeoffs that are important to you but I sure am glad I dont have an electric fridge in the trailer boat with the under 10 hp outboard somewhat weak charger. I would go from lots of DC power margin to very little.

I think I am going to make an ice chest setup for the type of trip I posted earlier where I would have easy access to purchase block or cubed ice and we might be on and off the boat for several weeks and want at least cold drinks in the boat during the whole time.

Sumner did a write up on the fridge he made using the hardware store foam. Im going to do something a little different (only 2 inches on any side and slightly different construction).

http://purplesagetradingpost.com/sumner/endeavour-inside-mods/page-1.html

The last two posters have the same boat as I and one other nice thing about ice chests is the flexibility. I could go from removing all ice chests to the setup with two ice chests that we used at Lake Powell for four people and nearly a week. 99% of the time now I only need that smallest ice chest which is nice - easy to clean and get in and out of the boat. When I build this new ice chest (which I really dont need.. but it will be a fun project), it will go in the same spot Im already using for ice chests.

I'm not sure a fan would offer any advantage. Heat likes to find equilibrium side to side.

Yes.. I think some sort of ventilation that allows air flow at the top and the bottom of the divider might be all you need - natural air circulation does a good job. Ill still put the fan in since it doesnt draw much power but with a switch so I can turn it off. I partly just want to see how much benifit I would get from the fan.

 

[walt]

Don't open the box and stare like the people at the grocery store do.

From my past experience, it will be best to just buy more ice if my wife wants to spend as much time as she dang well pleases looking in the ice chest. Best to not even bring this up..

However, I do believe I will have some sucess at training the dogs (and myself) to not do this.

 

[walt]

Update..

I went ahead and made this "electric ice chest" idea for my Mac 26S and have a little test time on it now with mixed results. The first picture shows the general configuration and there is a .75 watt fan blowing air over ice sitting on an aluminum heat sink in one chamber and the cold air comes in at the bottom of the larger food chamber. The second picture shows a mockup of where it will go in the 26S.

The good thing is that the chest is fairly good at transferring the cold of the ice to the food chamber. I had a little fridge thermometer in the food area and the temperature stayed about 44F - which is somewhere between where a fridge and an ice chest would run.

The negative result was that if I left the fan on all the time, I got just less than 2 days on a 10 pound block of ice. The ice chest has 2 inches of insulation foam on all sides so an R value of maybe 10 and for an ice chest, I think the ice should have lasted longer but I think that circulating air increases the heat flow to the outside. I had the lid clamped down during this test so no air should have been leaking in our out - except when I was checking things which was probably too often.

So.. just partly successful. It will still make a good ice chest and I put a switch on the front so that I can turn the fan off and on which I think will result in slightly warmer temps inside but the ice hopefully will last longer..

It ended up weighing 45 pounds and has nice "Wal-Mart furniture" styling

 

[Doc_holiday]

I would scrap the fan, the temperature should equilibrate on its own horizontaly.

 

[walt]

That is what I plan to test next.. just throw a block of ice in there and do the same test but no fan - check temperature and see how long the ice lasts. I put a switch on the front area so its easy to turn the fan on/off.

 

[Doc_holiday]

Can you get a block in the right dimensions easily enough?

By the way commercial refrigerators are normally 38-42 but 44 will be fine.

 

[walt]

The two sizes I had planned for (to hold two blocks) were

6 x 6 x 10

5 x 5 x 11

inches

The ice blocks Ive been finding at the grocery store are 6 x 6 on side. I just bought one and it weighs 11 pounds.

I had beer in that cooler for the first test and its "just fine" at 44F..

FYI, I looked up the 2 inch foam and it has an R value of 11. There is about another .5 inch of plywood total top and bottom and about .35 inch thick total plywood on the sides.

Does the plywood increase the R value much at all?

This link was just posted on this forum recently and this guy says a fridge should have an R value of 30 or so. http://www.kollmann-marine.com/Performance problems.aspx

edit - add some links besides Sumners link posted earlier
http://forums.bateau2.com/viewtopic.php?f=6&t=30496
http://www.cncphotoalbum.com/doityourself/icebox/build_icebox.htm
http://www.westsystem.com/ss/building-an-efficient-icebox-2/

 

[shemandr]

I had beer in that cooler for the first test and its "just fine" at 44F..

Are you sure? I would recommend another test of that parameter. And, how does it taste at 46F? 48F? And of course for any proper science you need a control say - 52F. Don't skimp on research!

 

[Doc_holiday]

The 1/2" plywood adds 0.62 and the 3/8" plywood is 0.47. Negligible.

The foam with the foil back is about 8 per inch. So 2" would yield 15-16 plus about 1 for your plywood.

 

[walt]

It looks like that without the fan, the temps in the food area are in the 47 to 50 F range (a little colder at night) and the 10 pound block of ice will probably still only last between 2 to 3 days.

This is without the fan running but I think that with the bottom opening and the top opening, there is still likely the natural circular air flow where warm air flows at the top from the warm chamber to the cold and at the bottom, cold air flows from the cold chamber to the warm.

FYI, Coors is still pretty tasty at 48F but 44F is definately nicer..

Not perfect.. but not too bad. Ill keep the fan with the switch in place for a "turbo" mode when I want the colder beer

Makes me wonder if the "five day" chests will really keep the same block of ice still frozen for five days???

 

[Kestle]

Just some off the cuff noodling:

1) it didn't sound like you either precooled either the food or the chest;

2) block ice has a lower surface area than cubbed. That'll make it melt slower.

3) the chest was not closely packed, so thermal inertia was lower.

4) I find it hard to believe you'll only get 2-3 days, as I can get that with a regular chest. So where could the air/water leaks be?

5) all ice chests and fridges are painted white inside. I wonder if that makes a difference.

Jeff