convert ice box to fridge- how hard?

[realem]

Not hard to do, great advise so far. Still need to know what climate you are sailing in. Battery power will have to be considered. I have two Hundred watt solar panels running danfoss compressor to cool 1.8 cu ft in South Florida. Two AGM 100 AH batteries. When the sun is up batteries stay up at 13+ , at night they drop down to about 12.03. By 9AM they are back up to 12.9. We can sit on the hook without the engine for as long as we like. Food stay cold, beer stay cold. No need to go looking around for ice.
When I installed it and converted the old ice box it was the end of the ice age

[psk125]

We looked into this for our boat earlier this past winter. It is feasible, and not too difficult to do, as others have said. The question is whether it will work for your needs. An electrical engineer reviewed our plans and essentially said that it would not. In order to keep the fridge cold while cruising, we would need to run the engine to charge the batteries at least two hours every day. That means two hours OR MORE. Otherwise, we'd have to be in a slip and plugged in. Without plugging in or recharging, we'd run out of battery juice after three days. That is not how we use the boat, and we know that ice in the icebox keeps things cold for about a week. Adding the cost of renting overnight slips to the cost of the system itself takes the whole equation into a different level. If we figure we can buy a lot of ice for $1500, (what a properly-sized setup might cost) how much more could we get instead of paying $20/ft for a slip every night? Hauling ice can be a hassle, but at that rate we figure we can put up with it for quite a long time.

[evm1024]

Just finished up a conversion. On a different boat of course.

I chose to cut the old fridge and counter out and rebuild from scratch. The 45 year old insulation looked like granulated raw sugar when you touched it. Read that as worthless.

I put in 6" of blue foam (XPS) for R-30 on 4 of the 6 sided. The top and front was done up in a mix of XPS and Aspen Cryogel to be R30 (4" total). XPS is R5 per inch and Cryogel is R10 pre inch.

The end results is a fridge/freezer that is 6.5 CU FT and is running about 30% duty cycle in the cold PNW. The freezer is set for -10 C.

[skipmac]

Originally Posted by silkie

I've seen ice boxes that had space for insulation, but no insulation was added. Just left as air cavities.

Yep. That's exactly what I found when I rebuilt the fridge in my boat. At least 2" gap, most places 3-4" but lots of the box was just fiberglass layer over a sheet of plywood with no insulation at all on the back.

I've read some formal procedure for testing how well your box is insulated but I would just put some ice in it and see if it melted in hours or days. Hours, add insulation. Days, go with it.

Adding the insulation can be relatively simple or a huge pain. When I overhauled my boat it was the single, most time consuming job.