What's the best modern freezer unit?

[Terra Nova]

Originally Posted by Jolly Roger

...After hacking through an inch and a half of glassfibre and ply...and still not reaching any insulation, I realized there was no way I could remove the whole top...
I therefore think the only way to increase the thickness is by padding the inside of the box and maybe also the outside of the enclosure on the three sides I can get to. Paul L mentions this method and I wonder if it would work for me?...
Will it be worth doing the same on the three outer sides or the enclosure, which I can get to easily?...

No and no.

You gave up too easy, trying to cut through the top. Your box was carelessly designed with no regard for efficient insulation. The structure that exists is only in your way--remove it and do a proper job of it.

[Dsanduril]

Originally Posted by Jolly Roger

...Will filling the bottom 12” with foam help, on the basis that cold air sinks?

Your overall solution is the time-honored way of trying to improve an existing box. Yes, if you had the time, energy, and money you could get a better result out of a new box, but there are lots (lots) of boats out there with exactly the solution you are proposing.

The key is to keep your new insulation dry. Whether you glass in place (which may be easier through a small top hatch) or use premade panels joined at the seams make sure you do a good job of keeping the water out of the insulation.

Which brings me to the question of the bottom, yes, nearly every construction book recommends maximum insulation at the bottom, and filling with insulation is not a bad way to go. But remember that this is where water also wants to go, see point above, you have to make sure you have a good way to keep that bottom section dry.

[Jolly Roger]

Thanks Dsanduril; There is already a drain in the bottom of the box, so I can extend this to the center of the new bottom and shape it so all water drains out properly.
I really do appreciate all this advice and I’m a lot wiser and more confident than when I started.
How’s this for an operation plan?
I start by testing the existing box with a 20Lb bag of ice placed where the evaporator will eventually fit and measure the temperature drop and melt duration. My wife reckons it will last three days from her past usage as an ice box.
Next I drill exploratory holes in the top and three sides of the outer cabinet and squirt foam in if required, bearing in mind Skipmac’s warning about expansion.
I then glue as much good quality insulation as I can get onto the outside cabinet sides, (at various points I should be able to get 3”), then measure again.
This will then be: ¼” inner box wall, 2” of foam, ¼” glass fiber, ¾” marine ply and another ¼” glass, plus two or three inches extra foam—maybe 6” in places.
Crazyoldboatguy mentions Polyiso from Home Depot. That’s easy enough, but is there a better product, if cost was no object?
Next I fill the bottom with foam, and measure again.
If the improvement is significant I buy an air cooled freezer unit and install it.
Then, depending on the run time, I can add an extra inch on the inside of the box.
At least, all this testing and measuring will keep me in cold beer.

[Dsanduril]

My opinion, and there are lots out there, is the polyiso is the best you can get in a traditional insulation. If cost is really no object you could line the inside with aerogel or VIPs, but that would really mean that cost is no object. My own box is foil-faced polyiso sandwiching VIPs (the polyiso helps provide structure and insulation where the VIPs butt at corners).

Doesn't matter too much whether the insulation is on the outside or the inside of the box, really the key is making it tight so that you don't get air flow that bypasses the insulation. If you're doing multiple layers, use staggered joints. At corners use "staircase" joints. Use some sealant at all of the joints to prevent airflow.

Your test will be interesting, as long as you have reasonably stable exterior temperatures it should at least give you some idea of the gain. Might want to go with two bags, first bag for one day to get the box down to a stable temperature, throw it away, add new bag, then start the clock. That way you don't count the time getting down to low temp, as that could vary if you have recently been working on the box.

[Jolly Roger]

Originally Posted by Terra Nova

No and no.

You gave up too easy, trying to cut through the top. Your box was carelessly designed with no regard for efficient insulation. The structure that exists is only in your way--remove it and do a proper job of it.

I won’t be accused of giving up too easily, and if you read my website you will see I have achieved some remarkable jobs, a few of which I was told were impossible.
But I do know my limitations, along with the physical limitations of the area where the box is. Because of the curve of the deck above it is impossible to remove the existing box without chopping it out. It would also be impossible to re-insert a new, smaller box for the same reason. So it would have to be built in-situ, which I cannot do.

[skipmac]

The ultimate, price is no object insulation are vacuum panels. Basically large, flat hollow panels with a vacuum. Expensive and if (when?) they leak and lose the vacuum the R-value drops 90%.

Several people have used stuff called Aerogel that has much higher R-value than polystyrene or polyisocyanurate (which is what I was trying to remember when I earlier called it polyurethane) panels. But I read that it is a pain to work with, makes nasty (toxic?) dust and is kind of compressible like a blanket so you need to support it.

I went with polystyrene for best compromise of features: overall ease to work with, easy access to the materials, reasonable cost and long term stability.

And yes, putting extra insulation on the bottom won't hurt. There is a point of diminishing returns on extra insulation but at the end of the day, except for higher cost and less room in the box, there's no down side I know to too much insulation.

[Jolly Roger]

Originally Posted by Dsanduril

My opinion, and there are lots out there, is the polyiso is the best you can get in a traditional insulation. If cost is really no object you could line the inside with aerogel or VIPs,

Thanks again Dsanduril: I'm not made of money, but I wondered what the cost comparison would be, consistent with the benefits. What is aerogel and VIP? Do you know a website I could look at.

[Terra Nova]

Originally Posted by Jolly Roger

...I do know my limitations, along with the physical limitations of the area where the box is. Because of the curve of the deck above it is impossible to remove the existing box without chopping it out. It would also be impossible to re-insert a new, smaller box for the same reason. So it would have to be built in-situ, which I cannot do.

At least you know your limitations. So have a professional do what you cannot. Don't Mickey Mouse it just because you don't know how to do it.

[Jolly Roger]

Okay, Skipmac answered the question while I was writing it.
Dsanduril; I'll do the test procedure like you suggest, starting tomorrow and report back.
This thread has been read by a lot of people, so I suspect others have the same ideas. I'm pleased if it has helped someone else like it has helped me.

[skipmac]

Originally Posted by Jolly Roger

Because of the curve of the deck above it is impossible to remove the existing box without chopping it out. It would also be impossible to re-insert a new, smaller box for the same reason. So it would have to be built in-situ, which I cannot do.

Similar space limitations including the size of the companionway hatch, forced me to chop the old box into four pieces. Decided to cut a couple of inches out of the width (depth was fine) to make room for more insulation and glass the four pieces back together. I made a mockup and designed the rebuilt box so I could get it in the cabinet and not hit the overhead but no way to fit it down the companionway. So covered everything and glassed the box together in the main cabin including lots of sanding, filling and fairing the inside and put it back into the cabinet with more insulation.

20/20 hindsight it would have been a lot less work (maybe a whole lot less work) to insulate the inside of the cabinet and build a new liner in-situ. Guess I'll know the next time I build a fridge in a boat which I hope is never.

[crazyoldboatguy]

The aerogel product is NOT toxic. However, it is fryable when handled and the material is so hydrophobic that getting it in the mouth is akin to trying to swallow a teaspoon of cinnamon powder, like the challenges we hear about. Filter masks would be recommended.

The problem with the VIPs, as has been mentioned, is that they are quite fragile and will eventually lose the vacuum, no matter how well they are installed. It might take awhile but when the vacuum is gone, the insulation is GONE. Even if installed correctly, movement and abrasion could result in loss of vacuum. If someone runs a screw into the side of the fridge box, not knowing there are VIPs on the other side, the vacuum is lost forever.

Aerogel is expensive. As expensive as the VIPs would be. I think it would be hard to install any insulation, including aerogel and VIPs thru your small opening, You will likely have to remove the top completely. At that point, some might say "to hell with it - I'm building a whole new box". Only some, tho.

[Jolly Roger]

Originally Posted by skipmac

So covered everything and glassed the box together in the main cabin including lots of sanding, filling and fairing the inside and put it back into the cabinet with more insulation.

20/20 hindsight it would have been a lot less work (maybe a whole lot less work) to insulate the inside of the cabinet and build a new liner in-situ. Guess I'll know the next time I build a fridge in a boat which I hope is never.

I'm really glad you said this, because we have been living in a building site for nearly four years, without getting out for even a weekend chug above twice. I have just finished some major trim work in the saloon/galley and didn't anticipate such a complicated job on a freezer.
I thought hard about doing what you did, but one limitation I didn’t mention is, “she who must be obeyed,” who has put up with a lot, and glass fiber dust is the worst thing to have in a living area—next to an irate wife that is.
So I’ll get it done all right, with the minimum of mess, and produce a tolerable freezer as well.

[skipmac]

Originally Posted by Jolly Roger

I'm really glad you said this, because we have been living in a building site for nearly four years, without getting out for even a weekend chug above twice. I have just finished some major trim work in the saloon/galley and didn't anticipate such a complicated job on a freezer.
I thought hard about doing what you did, but one limitation I didn’t mention is, “she who must be obeyed,” who has put up with a lot, and glass fiber dust is the worst thing to have in a living area—next to an irate wife that is.
So I’ll get it done all right, with the minimum of mess, and produce a tolerable freezer as well.

Approaching 5 years now on the total overhaul on my fixer upper. The only saving grace is we're still in the house and don't have to live in the middle of it all. Yes the fiberglass dust and such was really nasty and I'm still cleaning up piles of dust when I open drawers and lockers.

Of all the jobs on my refit the fridge/freezer was by far the highest number of hours, especially when I factored in all the planning, measuring, thinking, analyzing the project before moving to the next step. I spoke with another Pearson owner that did his fridge. His description of the job sounded tough, he rebuilt his from the inside out, leaving the exterior of the cabinets in place but as bad as it was, in retrospect it sounds like his method was a lot faster and easier than mine.

[Jolly Roger]

I did the following test over the past five days using 16Lbs bags of ice. These were about 18” x 6” x 6” which I placed on the shelf, half way up the box.

Wednesday:
2.30pm 76º (ambient)
5.30pm 52º

Thursday
8.30am 42º
1pm 42º

Friday
9.30am 52º
10.30am 52º New bag of ice
2.15pm 43º
6 pm 41º

Saturday
9 am 42º
4.15pm 42º

Sunday
9am 48º
2pm 48º

When the box was at it’s lowest the outside walls and lid were colder to the touch, but no signs of condensation on the walls.

It’s obvious even to my armature eye; the box needs as much insulation as can be fitted. So I’m now going to clad the three walls with foam and do the test again. This can’t be bad, even if we leave it as an ice box.

The question is, what insulation? Home Depot has a number of different sheets and I would like to buy the best for this job?

Someone suggested that instead of trying the insulate the bottom of the box with mixed foam, I should freeze as many plastic bottles of water as I can get in the bottom of the box, under the shelf level. A freezer unit should keep these frozen and reduce the freezable capacity? Is this viable or not?

[crazyoldboatguy]

Polyiso