Cold plate refrigerator frosting

[jimgram]

I had a cold plate refrigerator system installed in what was an"ice box". From day one the thermostat didn't seem to do much. We had food occasionally freeze and heavy frost was an issue. The freezing occurred when my little battery fan worked. Also it greatly reduces the frost buildup. I've been working on this 1990 Grand Bank for a few months. My marina is 4 hours from my home so I travel back and forth. The last time I left the boat I left the refrigerator on because it was loaded with some food and a case of beer (non-alcolhol). Returning to the boat I expected it's contenti to be frozen (battery operated fan). Sure enough, lots of frost buildup but nothing froze. Then I realized of course nothing could freeze - the cold plate could have been 20 degrees but nothing could be colder than the ice that was coating it - result: the beer was REALLY cold! Maybe I'll ditch the fan and let frost control the temperature. Any thoughts?

 

[Sax]

Yes, if the frost becomes thick enough, you would have an actual “icebox” for a refrigerator. Which may or may not provide sufficient cooling for your needs. In daily use, with multiple door cycles, I would think that the plate would be more effective at removing heat from the box than just a wall of ice. My Grunert manual states “if an ice barrier forms, it will be necessary to defrost the plate.” As you noted, cold plate systems cycle on plate temperature only, not on the temperature of the box. The plates will tend to frost up quicker if you have leaking door seals or do not have the drain plug installed in the bottom of the box. My Grunert system typically needs to be defrosted every few weeks. A heat gun or hair dryer makes the job go more quickly.

I do like your idea to use a battery powered fan in the box to circulate the cold air.

 

[mvweebles]

To summarize @Sax , if you're getting heavy frost without a lot of door opening, you have leaking door seals (some frosting is acceptable, though it usually melts in-between cycles). Reason being that warm air can hold more moisture than cold air. When the warm air from outside the box seeps into the cold fridge, the moisture condenses and freezes.

Small fans are always a good idea. I have a traditional 12v compressor and evaporator setup with a small 12v circulation fan connected to the compressor.

Peter