There are 11 different uses for fans in your boat refrigerator see Fans under parts heading on my web site.
6. Air Tumbling Fan
Conventional home chest freezers use wire baskets to allow natural air circulation throughout a box. Home refrigerators are designed to assist in air tumbling circulation by having some type of open shelving when the evaporator is located at the top of the box. The evaporator absorbs heat from the air then cool air descends absorbing more heat and rises back to the evaporator.
A circulating fan in a refrigerator
or freezer will not produce good results in a box without open shelving unless a series of standoff rails are placed on the walls and floor to provide a space for air circulation.
Top opening refrigerators and freezers on boats have poor air flow and therefore the temperatures will vary from side to side and top to bottom. Without air movement in a refrigerator or freezer, temperatures tend to stratify in layers. Most commercial
and home refrigerators are constructed to allow the natural movement of warm air rising and cold air descending across the evaporator to tumble the air. The addition of a small fan can help most refrigerated boxes. I recommend a one inch square muffin fan that runs at all times when the refrigeration
is in use. I ran over two hundred tests to prove what works and what does not. Many are in my 12/24 volt manual.
TUMBLING AIR FAN TEST:
The thermostat was locked and outside air temperature maintained between 79 to 82˚F. for these 24 hour tests. In test 119 the food product blocks the transfer of heat. In test 120 the small airflow from a one-inch muffin fan tumbling box air, lowered temperature eight degrees at the far end of the box. This fan also increased the efficiency of the evaporator and increased Btu output from the compressor.