Freezer

[Mike Bernard4136]

RichardI have 2000 Hunter 420 with a Grunert Polarmate model PMEAW08/12VDC refrigeration system (specs. say 433 Btu/h capacity at 20 degree evaporator temp and 246 Btu/h at 0 dregree evaporator temp.) with a spillover fan for the fridge side. The evaporator plate for the freezer is U shape and has a surface area measuring 40.5”X10 ¾”. The freezer is approx. 3.9 cu. Ft. and the fridge 4.5 cu. Ft. The freezer temp. ranges between 10 and 25 degrees halfway down the freezer depending upon how often it is opened, ambient temp. and how much frost is on the plate. It has never registered below 10 degrees. Energy consumption has not been an issue. My question is if I were to install a separate unit for the fridge, close off and insulate the spillover ducts, would my existing system be capable of making my freezer a true freezer and maintain a 0 degree temp?

 

[Richard Kollmann]

How Cold can a Freezer get

A second unit in the refrigerator is a good idea if you plan on cruising south of latitude 26 N. Your present Polar Mate has about the same capacity as the older Adler Barbour. The Btu figures quoted sound like the Danfoss BD35 compressor is set to run at 3500 max RPM. On production boats it is very difficult to operate a freezer in the tropics at zero degrees F. It will be the insulation that will determine how cold a 3.9 cubic box can get and not the compressor.I would run a performance test before making any changes.Connect a ammeter in series with the refrigerator power wire and read the current draw with the freezer temp. above 32 degrees. Then place a jumper across the thermostat and let the compressor run 12 hour straight. Before stopping the unit read the amp draw again. Record the temperatures in the freezer, refrigerator, approx. seawater temp. and cabin temp.The box temp. after 12 hours will be as cold as you could expect to get it.Check the exterior of the box for condensation and cool areas.Email me the information you have collected.