Refrigerating a large ice box

[Peregrine1983]

Hi all,

We have a 1983 Pearson 424 C Plan layout ketch with a large 15 cu ft ice box that I'd like to convert to a refrigerator and partial freezer, if possible.

We have 350 watts of good monocrystalline solar and a 450ah FLA battery house bank.

I'm thinking a holding plate system is the way to go. We cruise New England and I want to run the unit 24/7 all summer.

I'm curious which refrigeration systems you all with similarly large ice boxes are running and if you did anything to reduce the size and/or increase the R rating and insulation of the ice box.

Thanks in advance for any advice.

[Bowdrie]

Originally Posted by Peregrine1983

Hi all,
We have a 1983 Pearson 424 C Plan layout ketch with a large 15 cu ft ice box that I'd like to convert to a refrigerator and partial freezer, if possible.
We have 350 watts of good monocrystalline solar and a 450ah FLA battery house bank.
I'm thinking a holding plate system is the way to go. We cruise New England and I want to run the unit 24/7 all summer.
I'm curious which refrigeration systems you all with similarly large ice boxes are running and if you did anything to reduce the size and/or increase the R rating and insulation of the ice box.
Thanks in advance for any advice.

Oh boy, you're kind of between a rock and a hard place.
Advertising hype notwithstanding, I'm not aware of any 12V refrigeration system that can keep up with the demands of a box that large, except for a large belt-drive open compressor unit.
The electrical demands are horrendous, massive cold plates and engine drive compressors can work, but the lack of insulation vs the interior volume is a downhill curve.
The holding plate units from Technautics/Cool Blue may work, but it would require more than one unit.
That size of box is from an era when the common practice was to put in two or three hundred pounds of ice and take-off for a 2>3-week family vacation cruise.
A rebuilding of the box for less volume and more insulation is about the only choice for reasonable performance.
It's a miserable job no matter which way you go, either removing the existing box, or building a new and smaller box inside of the existing one.
You've got a winter project it seems.

[Stu Jackson]

Originally Posted by Bowdrie

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1. A rebuilding of the box for less volume and more insulation is about the only choice for reasonable performance.


2. It's a miserable job no matter which way you go, either removing the existing box, or building a new and smaller box inside of the existing one.
You've got a winter project it seems.

1. It seems like a logical approach.


2. It may not be so miserable at all if you follow #1 by installing a lot of insulation INSIDE the existing box.

[Peregrine1983]

Hah thank you Bowdrie and Stu for the replies. When it comes to insulating or compartmentalizing the existing box, what would be your approach?

The box itself is basically a large, plastic bin with a drain. The access is from the top and I believe there is about 4" of foam insulation on all sides. Would you do something like mold in a piece of insulating foam in fiberglass to partition the box?

I am in touch with Technautics and Sea Frost and it seems making the box smaller and settling for refrigeration only, rather than a freezer too, is the way to go.

As you mentioned Bowdrie, we've always just loaded it up with block ice and it does fairly well, but about 2 weeks in, we're always needing more ice up top to keep it cold.

[Bowdrie]

Originally Posted by Stu Jackson

It may not be so miserable at all if you follow #1 by installing a lot of insulation INSIDE the existing box.

It will only be less miserable if one does not mind several hours of hanging upside down trying to do fiberglass work.

For the OP.
I "believe" that that your galley was "stick built", in that the ice box is a fiberglass molding that was shot with spray-foam insulation, and then dropped into the cabinetry, then the countertop installed, right?
If so, and you can remove the countertop and lift out the box, (and this might be the determining factor,) all the work required to add insulation and new interior liner can be accomplished at the work bench, with far easier working conditions and much better results obtained with less overall effort.
There might be a "fly-in-the-ointment"; would the box fit thru the companionway, or was it put in the boat before the deck went on, which would require the work to be done inside the boat.
Some pondering/cogitating required before you make a decision on which road to take.
No matter the road, the top/lid can become the most challenging part of the job depending upon the insulative qualities and size of the original part.
Whatever path you take, you might peruse the offerings of "R Parts".
https://www.rparts.com/

[Peregrine1983]

Thanks very much, Bowdrie. I do believe that's how the ice box was constructed. I don't think getting it out the companionway will be an issue and I agree that instead of working upside down, hanging in the ice box, removing the whole unit would be good, but I'm concerned about taking apart the countertops - they may not ever be the same.

I was envisioning some sort of drop in liner, but even that gets complicated.

I spoke to some other 424 folks today, and I think I'm going to get an appropriately sized unit from Technautics and see how it does with the current ice box. Other 424 owners have had luck with this.

I think adding insulation wherever possible - such as rubber gaskets on the hatches, etc. will help.

[wingssail]

The simplest approach would be to leave the existing box in place and place new blocks of insultation inside of it, then glass a new liner inside of that.

I did this and I used closed cell foam 1 inch thick glued in overlapping layers, and a foil bubble wrap layer sandwiched in between layers, for a total of 5" of insulation.

Then I cut sheets of fiberglass and placed them inside the foam insulation, finally I tabbed all the corners to make a sealed, lined, box.

Leave no air gaps.

This is virtually a 1-day operation.

This reduced the interior size of the box significantly and the thick insulation made it efficient.

We installed a single air cooled Danfoss/Dometic unit with an oblong vertical evaporator which is the freezer area. This has worked exceedingly well. In tropical waters we use less than 75AH per day. In cold water areas we use half of that power. We can make ice overnight for at least 4 cocktails daily, and can freeze and keep frozen 24 servings of meat plus 1/3 kilo of coffee beans in the freezer area. Outside of the freezer we keep, beer, cokes, and water bottles ICE COLD, plus plenty of room for veggies, dairy products, etc in the remainder of the box. This is the arrangement we came to while circumnavigating, it works well for us.

Our box is small. If you start with your large one, even with 5" insulation, you will still have a large box and will likely be unable to run it on one small Dometic or similar unit. You could install two units and run one or both depending on the amount of power you have available and the ambient temperature (and sea water temperature).

My advice is to keep things simple. Simple approach to insulation, simple approach to the refrigeration units. Don't be swayed by "5% more efficiency". Simpler is cheaper and less trouble keeping it going.

[Chotu]

In case you go to the way of wingssail, I’m about to list a complete isotherm unit, Danfoss compressor, still in box, unused, on the classified section. DM me if you want it before it goes up

[Peregrine1983]

Thanks, Wingsail. That doesn't sound like a bad job. Did you keep a drain in the bottom of yours?

Chotu, I've been leaning towards doing a cold plate unit, but I'll DM you. Would love to see the specs on what you have.

[wingssail]

Originally Posted by Peregrine1983

Thanks, Wingsail. That doesn't sound like a bad job. Did you keep a drain in the bottom of yours?

Chotu, I've been leaning towards doing a cold plate unit, but I'll DM you. Would love to see the specs on what you have.

No, we did not keep the drain. Mostly that is needed for ice blocks and defrosting.

For defrosting we have a long hose on a Whale Gulper pump which we use as a bilge pump, but it reaches into the refer to pump that dry if needed. We don't put ice blocks in the refer.

Regarding cold plate, keep the system simple. Everything you add to make it better is just one more complication.

[Bowdrie]

Originally Posted by wingssail

Then I cut sheets of fiberglass and placed them inside the foam insulation, finally I tabbed all the corners to make a sealed, lined, box.
Leave no air gaps.

How did you seal the back sides of the fiberglass sheets to the foam so as to eliminate the back sides of the fiberglass from forming condensation against the foam?

[wingssail]

Originally Posted by Bowdrie

How did you seal the back sides of the fiberglass sheets to the foam so as to eliminate the back sides of the fiberglass from forming condensation against the foam?

I did not seal the back sides of the fiberglass sheets to the foam. I was unaware of that issue.

Anyhow, my experience with condensation is that it occurs when moist air hits a cold surface. The fiberglass would certainly be a cold surface but the air behind it should not be warm or moist, to my way of thinking, but maybe it is.

Anyhow, this is the kind of rabbit hole I refuse to go down: there are any number of ways to worry about whether or not this job is perfect, and lots of ways to pursue that little bit of perfection, and in the end you can turn every one day job into something bigger, and never get to go sailing.

[Bowdrie]

Originally Posted by wingssail

I did not seal the back sides of the fiberglass sheets to the foam. I was unaware of that issue.

there are any number of ways to worry about whether or not this job is perfect, and lots of ways to pursue that little bit of perfection, and in the end you can turn every one day job into something bigger, and never get to go sailing.

Ok, I understand your point about "going sailing".
Besides, the faster you can accomplish the miserable jobs the more time you have for important things like varnish and beer.

[Celestialsailor]

I have a Pearson 365. It's box is also huge. I'm going to install my cold machine with the BD50. I also know the box is poorly insulated. Because the station where the box is, is narrow, My only option may be to block off the furthest end of it and add a id over for can storage and add a false floor to make the bottom more reachable. I suspect I can reduce it to a 7 cu.ft. box and add vacuum panels.

[wholybee]

Originally Posted by Bowdrie

How did you seal the back sides of the fiberglass sheets to the foam so as to eliminate the back sides of the fiberglass from forming condensation against the foam?

You don't need to seal the sheets to the foam. You need to seal the foam airtight. So, if the foam is against the old liner, you create a new liner with fiberglass sheets, and seal all the edges of the sheets, and also the top of the foam with fiberglass there, so that it's all airtight, then you won't have a condensation problem.

But, if you leave the top of the foam exposed, or if there is a small hole somewhere that lets air it (perhaps from drilling a hole for the coolant lines) then you will have condensation problems.