Thoughts on 'Marine' Refrigeration

[happyendings]

This is an old thread but I have to report that I built a refrigeration system using a .8 amp (100 watt) dorm refrigerator compressor and its associated air-cooled condensor and ran it through an Alder Barber Power Plate holdover plate. The plate froze to -1 degrees Fahrenheit in less than three hours while the compressor ran at .78 amps/120 VAC. I have not had time to run it at 12 volts via a small inverter but I would expect to see about a 9 amp draw at 12 VDC. That is somewhat on the high side for a cruising boat but circuitry could easily be designed to run the compressor when the solar or engine power is present--this is already done on some DC units by changing the speed of the compressor. The power consumption would also be conserved with a very well insulated box as the unit obviously pulls down faster than 50 and 80 watt units. Cost would be vastly reduced by eliminating the Danfoss compressor and control units which are sold at prices that represent their current near-monopoly position as a supplier of 12 volt refrigeration compressor/condenser units.

[sailorchic34]

Gee I'm not the only one. I've been using a 3CF dorm fridge running on inverter for 6 years now. Uses about ~50amps DC a day, more in the Hot delta weather. But in Summer there is more solar hours too. I'm at anchor quite a lot, months at the time and do that sailing thing.

The basic mechanical compressor design between the 12V and 120V systems are the same. The main difference is the 12V is somewhat smaller displacement, so runs more then The 120V units. Too much heal may burn one out, but that has not happened to me yet. Think the wave movement, rocking the boat back and forth, lubricates the compressor well enough.

Don't forget to include the inverter losses, an extra amp for the 12V to 120V conversion. My basic magic chef fridge runs 10 minutes an hour (2.5 on every 10 minutes) in the heat of summer (93 cabin temps in the hot cali Delta). It runs less in cooler weather.

[happyendings]

I neglected to mention that this was a breadboard-type project. The plate was placed in a fairly dilapidated 150 quart ice chest, the lines were not insulated, etc. I didn't even use a small muffin fan to cool the condenser. I think 9 amps is about right including inverter losses.

Imho, this solution represents an economical middle group between two expensive extremes with fast pull-down, high powered engine-driven or A/C motor-driven holding plate units on one end and less expensive (but still not cheap) 12 volt units on the other .

[Ryan H]

I converted my ice box into a fridge/freezer by cutting a dorm fridge in half with a sawsall, cutting a hole in the side of the ice box, ran the cold plate where I wanted it, screwed the thermostat and sensor into the side of the box, fiberglassed everything back up, added 4" insulation outside the box, 1" insulation inside, wrapped everything in bubble foil, and mounted the compressor setup in a side cabinet. Gave me about 2-3 SF of freezer space and around 4-5 SF of fridge space. More than plenty for me. Between my solar, motor, generator, and turbine I've never really noticed much of a daily draw because of it.

I could post pictures of the process if anyone wants them.

[austinsailor]

There is another marine refrigerator around, it's about half the price of the "cold machine" standard. It uses the same compressor.

We've had one installed for about a year and it's worked as advertised.

I think the cost of compressor, coils and thermostat was about $700. Similar cold machine was about $1400. I've bought both new and it seems comparable.

I bought mine here:

Sure Marine Service, Inc. | Vitrifrigo AC/DC Marine Refrigeration

[gts1544]

Gentlemen; About two years ago we installed a small refrigeration unit into our ice box on our 1986 Beneteau 41 and powered it from our AGM house batteries that are kept charged by an Air Breeze wind turbine. We are in the BVI's and can count on about 10 - 20 knots of wind constantly. We are able to run the unit almost constantly with no depletion of house battery power. gts1544 - George

[phorvati]

I've taken one off the sidewalk on a trash day, and taken it apart to inspect and use parts as spares. Danfoss was 120V so that was useless. Dryer, and inspection glass was also useless. Some of the tubing was useful, and also the thermostat with the thermocouple. The only really useful thing I was able to salvage was freezer's evaporator plate that also had a capillary tub built in. Yeah the paint might chip away as you straighten it, but I was able to keep it in tact, and I keep that as my spare evaporator plate.
On the other hand i did take an AC unit off the sidewalk and after I took that apart, I was able to take a nice condenser coil plate with 1/4" copper tubing. Its huge. And if my current fridge condenser coils ever has a major malfunction, this plate would be an awesome replacement.

both were the R134a units.