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Old 23-11-2010, 08:37   #1
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Refrigeration Box Insulation

Hi, we are refitting our boat to go on an extended cruise next fall and one of the things I found on taking the boat apart to install equipment is a big air void between the hull and the icebox. it runs down the hull I think down to the stingers but cant see that far, A friend has a camera and I am going to use it to see how far the void goes, but to fill it what is the best foam to use? I know the expanding foam is pretty good, but I was told to be careful not to overfill. is there a specific product I should use?

As well we have a small evaporator oval freezer crewed into the top of the box, can only get a couple of steaks in there, clod air sinks, but could I use a dividing wall just in front of the evaporator to allow the section to fill with cold air enough to freeze or keep items very cold to last longer?

Mark
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Old 23-11-2010, 08:49   #2
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I used expanding foam to fill in a similar void on a previous boat, but it only made a small difference in terms of icebox efficiency.

The fears about overfilling tend to be blown out of proportion.
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Old 23-11-2010, 09:41   #3
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You don't say anything about what insulation you already have in place. This might be very helpful. But the fact that you refer to your system as an "ice box" tells me that you might be needing a lot more insulation than some expanding "space filler". There's a lot of information here on the subject. The wrong insulation can be heartbreaking... and expensive. Suggest you look into Extruded Polystyrene Foam, if you're actually needing insulation. But I don't know where you really are in the process.

It cost a lot of money to make cold. Throwing the cold away with a quick and dirty insulation job cost a lot more than money, said they guy who had been down that road.
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Old 23-11-2010, 09:46   #4
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Thanks, This is an existing icebox type fridge,, I dont know the type of insulation that they used when they manufactured it from the vendor?
The boat is a Beneteau Oceanis 370, so a production boat.
I didnt really want to rip it out and have someone put in a new one, with all of the things we are doing to get the boat ready I have to balance out my money and do everything.

What is the foam you are talking about? I will also look in the forum for information as well,

Mark
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Old 23-11-2010, 10:03   #5
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Quote:
Originally Posted by fawcettm View Post
... What is the foam you are talking about?
For instance, Dow's “Great Stuff” expanding foam insulation
Spray Foam Insulation | GREAT STUFF? Insulating Foam Sealant
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Old 23-11-2010, 10:43   #6
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For instance, Dow's “Great Stuff” expanding foam insulation
Spray Foam Insulation | GREAT STUFF? Insulating Foam Sealant

Well,.. no. I believe that's the foam Fawcettm was talking about, but not me. I'm talking about the "blue" or "pink" board.

I under$tand the balancing act of what you're going through. I'd just hate to see you wind up with a fridge unit that drains your electrical system because of a "quick and dirty" insulation job. Believe me, you will loose sleep over it.... if you get this part wrong.

I've seen people throw a lot of money at annoying charging systems because they just figured getting the fridge insulation was too much trouble up front. And their charging systems STILL left them with the problems.

IF your really need proper insulation, & IF you're not up to an icebox rebuild, I'd suggest you look into a stand alone unit. They can be very energy efficient. I personally have a Fridgefreeze unit, in addition to a..now... well insulated and efficient box. There's also Engle and others out there that people are happy with.

The expanding foam may in fact be all you need. But from what you say, I'm reading, old production boat with sad icebox, about to be sadder because of expanding foam.
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Old 23-11-2010, 11:50   #7
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Interesting, I thought the spray foam gave a R value. sound like I need to read more in this forum and decide to look at the overall box, I cant imagine building a new box and the work needed to rip out the old one, believe me I tried to take some of it apart the past couple of weekends and it is put together tighter then a you know what! I spent hours trying to figure out how they assembled it all and after it all was scared I was going to destroy what was there and then pay someone to fix it, with my limited budget I still have other things to buy.

I know I probably will use more energy in the tropics, but I dont want it to run all of the time, nor do I have a couple of thousand to spend on redoing the box and new refrigeration cause if I was going to do that it probably would be a good idea to update the compressor and evaporator as well......

just looking for the biggest bang for my buck, and researching more will help with that.

I see from searching that there seems to be this question asked every few weeks or so.....

Mark
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Old 23-11-2010, 12:09   #8
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The spray in, expandable foam (a urethane foam) does add R value, BUT it also absorbs moisture readily and over a relatively short time the insulating value will drop a lot.

Unless something new has hit the market it seems like most bang for the buck as far as cost, R value, and long term stability seems to be Dow blue board or equivalents. This is a polystyrene foam.

Another option is vacuum panel insulation. Great R value but very expensive and can be damaged and lose all their insulating property.
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Old 24-11-2010, 12:44   #9
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The void behind may not matter. What counts is the insulation and thickness in the ice box. This needs to be roughly 4" for a fridge and more for a freezer depending on temperature. You should be able to determine the thickness of the ice box. What you may find depending on the design is that there is are voids or even no insulation. This why some recommend starting from scratch. Have just done mine. There were voids or even no insulation behind two walls. I drilled holes and filled it with aerosol foam. Then added 40 mm of polyurethane board and 80 mm on top where there was none. The insulating effect is proportional to the thickness which should be uniform. That is not 4" in one place but 2" in others.
The difficulty is that working it out say in a 1 ft by 1 ft by 2 ft box you get .5 x .5 x 1.5 ie .6 cu ft instead of 2 using 3". It won't be quite that bad because you should have 2" or so space outside the inner box now, but it still makes it much smaller.
As space is the constraint you are better using polyurethane than polystyrene. Vacuum panels are out of range.
Cost in materials for a small box is quite high, around $400 NZ or 300 US plus paint which is also expensive. I used gelcoat which is not completely waterproof but I plan to minimise water by using sealed ice containers before I add a compressor etc if I need to. That is not ideal but the paint would be another 200 or so.
An overflow system from a smaller better insulated freezer part may work. You don't need everything frozen but some bits like steaks are good.
It also takes quite a bit of time working in situ and is harder than making a box from scratch. Also very messy.
You need to work out what you have in insulation and what you need. You may well cut your power use by half or even more.
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Old 24-11-2010, 13:27   #10
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You really do not want to use the "insulation expandable foam" that comes in those cans from Home Depot or other hardware places. I know because I did use them and after a few years of heat and time, the foam shrinks as much as 50% and breaks down. It does not expand uniformly and makes a mess of cavities and coils much like what a human intestine looks like. And has about the same insulation properties. In a land home it is used to close an air passage to stop the wind from entering the house.
- - As stated above water and moisture get into the spaces between the coils of extruded "worm" and then your R-value goes to 1.
- - You can purchase two part polyurethane foam from boat supply stores, mix it together and pour it into the area. But it has to be done carefully as again it will try to assume a spherical shape as it expands which means it pulls away from walls and bulkheads. Multiple pours are needed to get a complete fill. The biggest problem is if you do not have strong walls and an open top the foam will expand and press/crush against whatever is containing it. I poured some under a floor board and used too much. As it expanded it raised the floorboards and popped up all the nails/screws. What a mess. The stuff is powerful.
- - Redoing a refrigerator or freezer insulation really means removing all the top or most of the surrounding wood walls/tops and gaining access to the box. Then the best material is, as mentioned above, the Pink or Blue Board panels cut to fit and encased in waterproof plastic "bags." It is an involved and not a quick job. But when done correctly you get a more efficient refrigerator/freezer.
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Old 24-11-2010, 13:45   #11
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Originally Posted by osirissail View Post
You really do not want to use the "insulation expandable foam" that comes in those cans from Home Depot or other hardware places. I know because I did use them and after a few years of heat and time, the foam shrinks as much as 50% and breaks down.
My experience was similar. It would have been better to do it right the first time. Instead, I tried every shortcut: bigger compressor, expandable foam, added battery capacity. The only thing that ultimately worked was selling the boat. If I had it to do all over, I'd start by re-insulating the box properly.
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Old 24-11-2010, 13:58   #12
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My experience was similar. It would have been better to do it right the first time. Instead, I tried every shortcut: bigger compressor, expandable foam, added battery capacity. The only thing that ultimately worked was selling the boat. If I had it to do all over, I'd start by re-insulating the box properly.
Indeed.
As someone very near & dear to me once said:
""If you didn't have time/$ to do it right in the first place, when will you get the time/$ to fix it?"
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Old 24-11-2010, 15:03   #13
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dont use the spray foam, it absorbs mositure. You need extruded polystryene sheet. ( not the expanded stuff). This is the Dow blue board. This and many othe rmakes are available in most building materials suppilers as its sold as house insulation. 4" is about whats needed to get R valued 4->5. ( note US R values are 5.67 times SI R values).

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Old 24-11-2010, 15:44   #14
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With all that said, the stand alone fridge unit should be looking pretty good right about now. That's a whole other discussion.

I'm NOT talking about a mini/apartment type for $100+ USD, but a chest type 12 VDC Engle, Fridgefreeze, Waco or other. More than the cost of a couple of cans of expanding foam you were hoping to get away with, but cheaper/faster than a box rebuild... and you get to dump a major cruiser concern of refridgeration/power consumption.
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Old 24-11-2010, 16:02   #15
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I agree with most of the advice you are getting. Don't bother with spray foam, you may as well stuff rags down there for all the good it will do. What you really need at a minimum is poly blue board or similar. otherwise you may as well pump cold air into a cardboard box and call it your fridge.
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