DC refer

powersupplyguy Registered Users Posts: 3
In am looking at going to a DC refer.  What is available out there?  I see Danfoss has 48v compressors.  I am curious if it is possible to retrofit an existing big box store refer with a DC compressor. 


  • BB.
    BB. Super Moderators, Administrators Posts: 33,404 admin
    Welcome to the forum PSG,

    The short answer, if you have a knowledgeable refrigeration technician, and he goes over the specifications of the appliance and the compressor--It should be doable...

    The next question, is what kind of fridge or freezer do you want to get? Manual defrost--A DC compressor may save you some energy (inverter losses). If you get a frost free model with door seal heaters/ice maker/etc... That would be a less trivial conversion.

    Frost Free refrigerators--They need to defrost about every 24 hours, or they start to build up frost in the evaporator pretty quickly... And the defrost heater takes something like 500-600 Watts (a Calrod heater or similar) to quickly melt the ice without heating the whole cold space.

    If you are looking at 48 VDC battery bank--Frequently, that is a a large enough off grid solar power system that energy possibly saved by conversion to 48 VDC may not be worth the time and money...

    Energy Star rated refrigerators use only a bit more energy than a similar sized DC fridge. And they are much cheaper--And you have lots of options (ice maker, size, door configuration, frost free, etc.).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    Energy star fridges use a bit more for the same size assuming similar construction and features.  Stuff like water/ice through the door put fridges in a different class for ES rating, and can add a lot to consumption.

    A simple, well sealed and insulated box and DC refer can save a lot.  Mine uses ~200wh/day as a freezer, vs 1.5kwh/day for a small (but older) manual defrost AC fridge/freezer.  

    Defrosting can be a nuisance.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    The new generation if Inverter type fridges are making both in the starting as well as the running current.  Total KWH use is pretty good too, and they can be had everywhere including the big box stores at very reasonable prices.  These days there is little incentive to buy exotic “solar” or DC fridges IMHO.  I am going to move away from propane when any of mine fail.