A two-week test was conducted on a boat under warm weather conditions  The seawater temperature varied from 81 to 86° F. The ambient temperature varied during the two weeks from 80 to 98°F. in the day time.

The system tested was insulated with vacuum panels one inch thick and one inch of Blue board insulation. There were two boxes with independent temperature controls. The refrigeration equipment consisted of a ¾ HP. 12-volt water-cooled condensing unit.

The freezer was 6 cubic ft. with two large holding plates. The refrigerator was 9 cubic ft. with one large plate. The refrigeration system was manufactured by Grunert and the vacuum panels, lids and frames by Glacier Bay.

The Temperature Data Logger was placed on a shelf midway up in each box for a one-week period the results of temperature and time are displayed on the graph in Figure #2

 TWO WEEK TEST OF VACUUM PANEL INSULATION

The first and second day the refrigerator was run twice an hour in the morning and ten minutes in the afternoon. The third day is more typical a one-hour run held over 17 hours. A previous test had determined that the air temperature in the refrigeration was too warm at the top. This test was done with a small circulating fan running continuously in the refrigerator. The performance of the refrigerator was good except for condensation coming from the double sealed side-opening door.

 In the freezer it looks like a typical day would require a 1½ hr engine run to provide a 21 hr. holdover. This would result in a mid box temperature swing from 9 to 18 degrees F.

After the thermostat stopped the compressor there was an additional temperature pull-down of the holding plate for 30 minutes. This additional bonus comes from the use of  409a refrigerant, a lower temperature refrigerant than 134a.

ADVICE GIVEN TO THE OWNER

Set both thermostats colder than they are now. If they won’t adjust to a colder setting slide the cap tube of the thermostat out of the holding plate a little until the problem is corrected. Too much metal-to-metal contact of the tube with the holding plate will cause the thermostat to shut off to soon.

 Proper thermostat adjustment is important when living at anchor to reduce engine run time. During the daily run they should not cycle and they both must run at the same time.

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