Like most electric motors, the refrigerator motor will use a high current when starting up, after which the current will drop back to the continuous use level. Refrigerators and freezers may be rated with the current they will use when the motor is running or they may have the average consumption per hour listed. When you arrive at your boat the refrigerator will have to run continuously for an hour or more before it gets down to its normal operating temperature after which it will run intermittently. Typical small boat fridges will consume around 5 to 6 amps per hour, although during the time the motor is running the consumption could be as high as 14 amps, so the circuits must be rated higher than this to cope with the higher starting power needed.
Boat refrigerators are one of the few motor units on board which run on a more or less continuous basis. This means that when the engine is stopped it will be one of the main users of current and the most likely cause of a dead battery if care is not taken. Some refrigerators include a device in the control circuitry to warn if the battery voltage is dropping. In some cases this will automatically switch off the refrigerator this occurs, in order to prevent the battery from becoming तो deeply discharged.
A prime example is the Adler/Barbour line. All sailors that have refrigeration on there boat know of this brand. That's because most sailboats have an ice box, that has been converted to a refrigerator. By using a combination of the COLDMACHINE CU-100 or the SUPERCOLDMACHINE CU-200 which both will accommodate large refrigerators—up to 15 cubic feet with 3” of polyurethane insulation. However; most sailboats do not have that 3” of polyurethane insulation. So we tend to compensate with the evaporators. The VD-150 Small Vertical Evaporator and the VD-151 Small Horizontal Evaporator both will refrigerate up to a 9 cubic foot ice box. Where the VD-153 Large Horizontal Evaporator or the VD-152 Large Vertical Evaporator these will will refrigerate up to a 15 cubic foot ice box. The open space in your ice box and the door layout will determine if you use a vertical or horizontal evaporator. On our original Catalina 36 (Silent Dream) we have the advantage of using either direction evaporator but it most be the large type.
With a larger ice box you could also make half of it a refrigerator and the other half a freezer by using the following items from Adler/Barbour.
First you would have to make a divider to fit your ice box, then by using the Digital Automatic Spill-over Fan kit C7210D and the Automatic Shutter D7230, you will end up with a side by side refrigerator in your sailboat. The last item we should mention for those of you in a warmer region is the SUPERCOLDMACHINE Cool Water Kit C8350 this little pump runs sea water over your condenser fins to help cool the condenser.
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