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Howard

Ice Box Design

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Foam expansion - for poly foams you should try a spritzer bottle - as in trigger spray style. Fill with water and mist the pour ... wait a bit, then pour more foam mix and as it starts to rise mist with water. In my experience the water misting causes maximum expansion and thus a lighter density which equates to better insulating qualities as well as lighter weight per cubic foot. Water mist works on squirt from aerosol can foam and 2-part mix foam.

That said I would go with coolers. Upside, when beached at your fav sandy hangout you can drag cooler of chow and adult beverages ashore and gather around the campfire - built below high tide line - and have at it!

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Do you know the R value of the poured foam in the first place? It's not obvious to me how the degree of foam expansion affects insulating ability when thickness is constant: more expansion means larger air bubbles, which speeds convection, but less solid foam to conduct--hmmm... I would keep moisture out of the foam simply by sealing the foam up tight. Since the speed at which heat enters your cooler is directly proportional to the temperature difference, you can use the results of your indoor test to extrapolate to any other temp difference. If the ice melts in 6 days with a 30 degree difference, then with a 60 degree difference (God forbid!) it will melt in half that time. (Of course, that's when you most desparately want the cold drinks!)

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Misting with water? First I've heard of that one, but it may work. Gorilla glue seems to be a close relative of the two part polyurethane foam and it benefits from and becomes more active with additional moisture.

The beach party sounds like fun, but that is a different use than I have in mind. I say we go with that in additional to the long term cooler I'll have on the boat. :P

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Ready to test:

Picture018.jpg

and inside.......

Picture021-1.jpg

I'm using a plastic milk crate, to line the bottom. I estimate it will hold about 20 pounds of crushed ice.....30 or 40 pounds of block if packed tight. It would also hold 4 gallon jugs (about 25 to 30 pounds) of frozen water, which could later be drank. Plastic tub is from a restaurant supply store. About 10" x 12". This was a popular size. Next size up was 12" x 18". If you sized that to fit close to the sides of your box, it could rest on the ice below and isolate the ice from the warm air entering. The more ice, the less warm air to enter.

Once this gets cooled down, I'll report on the tests I hope to run (retained melt water vs. drained out) and also will actually use it for a cooler with drinks, etc., so it gets an honest use test to see what the holding potential will be.

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Jeff:

I've seen R values for the two part poured foam of 6 to 7 per inch. I'm estimating 6. R value of the rigid pink foam board is 5 per inch.

BTW, the two part polyurethane foam is tough stuff. Said to be impervious to most solvents, heat and flame. By comparision, the pink stuff will burn and is apparently damaged by sunlight and temps as low as 150 degrees or so, and I suspect that polyester resins (like Boat Yard) and solvents like acetone will eat it alive. I tried a sample of Brightsides paint, and so far, it has resisted damage from that. But if I was going to paint near it, I'd still use a two part epoxy primer and maybe leave it at that.

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The r-value of Celotex foil faced foam board is 7.2 per inch. I used it on the inside of my 2x6 walls, under the wallboard, for my addition. I don't think there is a product for any reasonable price that is any better. There are some vacuum packed custom made panels that are considerably better, but they cost a fortune and have to be custom made to your specs. Pour foams have their uses. I don't think insulation is a particularly good one. There is always the chance for voids, and you will never know if you have any. And, as you have found out Howard, they have a very destructive nature during expansion. I have seen them blow out cabinets when poured as a securing method for fuel and holding tanks.

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On the foil vaced Celotex, I'd be curious to know what the structural load bearing characteristis are. As near as I can tell, all ice box designs are "free floating" which is to say the interior ice box itself is structurally isolated from the containment box. Wood or anything else that might be used to support it would also conduct heat and cold, so the insulation itself has to bear the load, which is a "live load" when you are talking about 40 to 50 pounds of ice and contents banging around inside the box. If Celotex can handle it, that might be a way to go. Several layers would mimic the foam/foil combo of the Pardey system (which is not their system.........they copied it from a Newport Beach, CA metal working shop that builds stainless steel tanks and stainless lined ice boxes for fishing boats).

I did some checking and the Foamular 250 (25 psi) product is the highest density product available locally, without making a special order (full bundle of about 25 sheets or so). But it looks like that would be adequate to be structural for this level of load.

BTW, almost any reasonable sized box could be built from two 4' x 8' sheets of foam and they sell locally for $26 per sheet or $52 for two. A comparable quantity of the 2 part foam (8 cubic feet of 2# foam) sells for about $70, plus shipping. In the big picture, not much difference in cost, but what there is leans in favor of the rigid foam insulation.

The only complication I can see, is if you go back through this thread and look at the pvc drains I used, building one of those into the rigid foam insulated box would be a neat trick. You could leave a bit of a gap and use the two part foam (or can of spray foam) to fill in around that. Most drawings of ice box systems I've seen drop the drain pipe straight out the bottom and put the loop outside (and below) the insulation. Simplest to build, but among other things, that puts the outfall low in the boat so it either has to drain into a small container that has to be dumped, or as some try, into the bilge. Draining into the bilge is nearly universally condemned as a bad idea (organic matter in the melt water will stink to high heaven). Some will pipe it to a bilge pump to be lifted out.

My hope was to elevate the box and drains just enough to get them above the water line to allow gravity to take care of it.

On the high end expensive vacume panel ideas, the maker of those was apparently Glacier Bay. A check of their website (different from the link in Calder's book) suggests they no longer make these. In fact, it looks like they are out of the insulation business alltogether.

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On the foil vaced Celotex, I'd be curious to know what the structural load bearing characteristis are. As near as I can tell, all ice box designs are "free floating" which is to say the interior ice box itself is structurally isolated from the containment box. Wood or anything else that might be used to support it would also conduct heat and cold, so the insulation itself has to bear the load, which is a "live load" when you are talking about 40 to 50 pounds of ice and contents banging around inside the box. If Celotex can handle it, that might be a way to go.

It is very structural. It is used for insulating foundations and has the back fill right up against it. Care needs to be taken with rocks during back fill as they can dent the foam, but it stands even loads like gravel or your ice box liner very well. My wallboard is attached over the foam with only fasteners through it. It is the complete thermal break (no wood penetration to the wallboard as without the foam) as well as the added insulation that are the main points of using the stuff in residential building.

Using can spray foam to fill voids caused by plumbing and such can be a good idea, but be careful. Exploding or distorting things is worse than a small void. I have found people distorting door jambs in the process of sealing around them with the stuff. Now the door doesn't close properly if at all which slightly negates the whole point of the process. I prefer a loose chink with fiberglass myself. Using foil tape in corners and such to secure the pieces together and seal off joints from heat infiltration is a good idea. Using a herring bone pattern for lapping panels at corners is a good technique as well.

I still think your intricate drain system is costing you as much in lost insulation integrity as it saves by being within the insulation. I would go straight out the bottom and maybe insulate the line to and including the trap.

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Update: After 5 days, the box has accumulated about 2 inches of melt water in the bottom. This test is of the side drain, retained melt water mode. It should accumulate to about 4 inches of melt water before it starts running out. It was "charged" with 25 pounds of ice cubes. I've been opening the lid about once a day to check on progress. Until the drain tube is "charged", it is allowing cold air to seep out through the drain tube. A quick set of calculations would suggest the 2 inches of melt water amounts to about 12 pounds, so about half my ice is gone. That looks about right.

On the topic of foam insulation, I'm rapidly warming to the idea of using the rigid foam vs. the two part poured. I did a water test of the two part foam, filling one of the mixing tubs I used with water. After only 4 days, a tub that weighed 150 grams had gained weight to 155 grams, suggesting to me it was absorbing water. Not good. I've also been driving around with a piece of the 15 psi pink sheet in the back of the truck. It has a similar sized piece of flat steel riding on it, which has a raised cleat on it (think cleats on a horse shoe). I thought the cleat would easily have punctured through the foam but it didn't. Even after doubling the weight, it has only dented it, and not by much. I have no doubt the 25 psi stuff would easily support the weight of a fully loaded ice box without deforming. BTW, Lowes has the Dow Brand blue board (called Scoreboard) in a 2" thickness. It also has a 25 psi load bearing rating. At $33 a sheet, it was more expensive, however.

On cutting the foam sheets, it turns out there are much more accurate ways to cut the stuff than using a utility knife. The model airplane guys like to use foam for their wings and use hot wire cutters to cut them (very precise cuts).

http://www.youtube.com/watch?v=910mYEhNMR4&feature=related

The power supply matched to the size and length of the wire appears to be the key to making good cuts, along with the right kind of wire (many use stainless steel fishing leader). But with such a system, you begin to see how very tight fitting pieces could be cut, which stands out in importance when you start thinking about how to cut the foam to fill a lid. With a hot wire, you could easily do an accurate stair step design or a tapered drop in plug......both of these are suggested as ways to tightly seal up the lid to prevent warm air from entering through the access lid.

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Test report:

After something like 10 days, box still had some ice remaining from the first 20# charge. Holding about 4 inches of water in the bottom, it never did start to drain so the remaining ice was sitting in water. Recharged it with an additional 20# on Sat and the syphon drain loop worked as planned. Pulled out all but about an inch or so. After three days, it has begun to drip. Now that it is running, I will do a 24 hour timed collection amount to compare to the melt rate from the bottom hole, where melt water is not retained.

At the same time on Sat, I dumped an additional 20# into my 54 quart Igloo cooler to see how long it would last for comparison. It went 2 /12 days before it had all melted. They were sitting side by side in the same room. Same test conditions...both left closed up. Crude estimate is I would get 3X to 4X as much use out of the same amount of ice with a well insulated built-in box, vs. the cooler. On a boat I'd be staying on for days or weeks at a time (vs. only short term use), that would be justification enough to me to build a well thought out, well insulated ice box into the boat.

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Crude estimate is I would get 3X to 4X as much use out of the same amount of ice with a well insulated built-in box, vs. the cooler. On a boat I'd be staying on for days or weeks at a time (vs. only short term use), that would be justification enough to me to build a well thought out, well insulated ice box into the boat.

Agreed... I think that's an amazing improvement. Based on nothing but my gut instinct, I was guessing you were going to get about 8-9 days of performance. I'm really impressed it went 10 and still had ice remaining! That's excellent! That would certainly be more than adequate for my needs. Does that meet your requirements? Or are you looking to extend it further?

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Keep in mind that was not opening the lid beyond once a day to peek inside. It was also ice cubes vs a block. I'm freezing some blocks in plastic wash tubs and may be able to get 30 to 40 pounds of block ice in about the same space, so in a test under these conditions it may run well beyond 2 weeks with solid ice. That may translate into a week to 10 days under normal use.

Anything over a week would suit me. I'd go back to the size calculations. Given the space, I'd opt for 6 inches of the rigid foam sheets and probably a 13" x 18" box around 18" deep, leaving a counter height of at least 30 inches. But space and weight considerations will ultimately decide what gets built.

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I moved the box to my furnace room (to be near a floor drain) where the ambient temperature is a steady 65 degrees. It is right next to the furnace, however, and likely gets a bit of radiant heat gain as well. Foil insulation should be dealing with that.

It is apparently sealed up well. Pulled the lid the other day and water shot out, suggesting the lid fits tight enough the draining melt water was pulling a vacuum.

Rate of melting has picked up to well over a quart a day. This 20# charge isn't going to make it past 7 days.

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Time for an update.

Looks like the rate of melt I get when leaving 4 inches or so of melt water in the box is just under 1 quart per day. Rate of melt from the bottom is about .75 quart per day, so getting the water out prolongs the ice a bit. Not much, but some. Doesn't seem to matter much if the box is full of ice or half full or only partly full. Rate of melt water draining out is steady. But this does seem to confirm that the botom drain and getting the water out is best.

Block ice and cubes melt at the same rate. A quantity of cubes (at least those from my ice maker) weigh about 60% that of an equal volume of block ice, so using blocks will extend the rate simply due to the density. This box will hold about 50# of solid ice, so at the rate of melt I'm getting, it should hold a full charge of ice about 22 days or so. But opening the lid for use lets in warm air, so realistically, any use is going to drop that some. Have not tried using it like that yet, but I'm guessing a guy could get 10 days to 2 weeks out of 50# of solid ice. Less of course, if whatever goes in is not chilled first.

Fun stuff.

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Ice melt stayed on schedule. As of today, about 21 days after the start of this test, I still had a round glob (an industry term) of ice left. (about the size of a cantaloupe). Got that out of about 50 pounds or so at the start.

Probably ready to wind down this test and have ideas for another one. If so, will revive this thread to do it.

Thanks to all for the comments, and suggestions! I learned a lot.

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