Making this fridge a little more efficient

Surfpath
Surfpath Solar Expert Posts: 468 ✭✭✭
in Solar Beginners Corner #1
So,
I have a ~9 cu ft Frigidaire fridge with freezer on top (doors open on the front of the unit) that draws 1.40 KWH/d. Would like to keep it a few more years, but ideally reduce its consumption a little (say, to 1.25 KWH/d). I remember reading how folks have managed to tweak their fridges to achieve this kind of gain.

We minimize the amount of time the refrigerator door is open, made sure that the unit is in a 'cool' space, not near a heat source, has enough circulating air in the back, and keep the freezer about 2/3 full at all times.

I havent done this yet, but I will clean the condenser coils & check the seals.

The obvious:

Stick back on the K-A-W meter and experiment with the fridge dials. Are my settings low?

Per the EPA: The [fridge] temperature should read 35 to 38 degrees F. The freezer should be between 0 and 5 degrees F.

Any other suggestions:

What about some external insulation?

My freezer has automatic defrost. Upon touch it appears that the sides of the freezer get hot when defrost is on, but not the back. The back seems to be always cooler than ambient temps. I guess I can stick my thermometer to the back and see if this hunch is right.

I have some R11 insulation. Do you think it will be worth my time to add a piece of this batting (sized as large as the freezer compartment) to this back area?

Note: the condenser coil is not located behind the freezer compartment, it's below, behind the fridge

Don't want to jump the gun and do anything silly. Thought I'd check here first ;)
Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #2
    Re: Making this fridge a little more efficient

    If the sides/top of the fridge get hot--Then the condenser may be under the metal skin--and it would not be a good idea to insulate the sides and top.

    Some people have good luck using closed cell foam boards on refrigerators that do not use the skins to get rid of heat... But I have always seen problems with moisture collecting under the insulation and causing rust and water logged insulation. You can try it and see what happens. If it gets hot under the insulation, then that is a no-go.

    If you store food in the freezer section for only a few weeks at a time, you could look at allowing the freezer temperature to go up a bit... But if you are using it for long term storage (6 months or more), 0F or colder appears to be the way to go:

    Question - Best Freezer Temperature

    Otherwise, I am not sure what you can do to improve performance. If you interrupt the defrost heaters, I think of the folks here reported that the evaporator coils froze over with frost/ice in 24 hours. Some refrigerators had a switch that turned on/off electric heaters round the doors (to reduce "sweating" or condensation during humid summers).

    If you are making a lot of ice (using in an ice chest for over flow keeping things cool, etc.), that can up the power usage a fair amount too.

    Sort of getting a newer/more efficient refrigerator or converting a chest freezer to a refrigerator, I am not sure what else you can do.

    Chest freezer     as a chest refrigerator
    Chest freezer to refrigerator conversion w/o new thermostat
    My latest freezer converted to fridge showing VERY good results

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Volvo Farmer
    Volvo Farmer Solar Expert Posts: 209 ✭✭✭✭✭
    #3
    Re: Making this fridge a little more efficient

    I have often thought of using a digital house timer to replace the factory defrost timer and experiment to see what happens. If you live in a dry climate, don't store open liquids in the refrigerator, and don't open the door a lot, I think it might be possible to double the amount of time between defrost cycles. The problem is, eventually the frost gets thick enough on the evaporator coils that you are actually loosing cooling efficiency because you have air blowing over ice crystals instead of over cold aluminum.

    It would take a lot of experimentation, with removing the evaporator cover from time to time to check frost build up, but in some circumstances, I think efficiency could be improved in this manner. Defrost systems are typically designed for worst case scenarios, moist environment, etc, and I believe there is room for improvement if your set of circumstances is better than worst case.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #4
    Re: Making this fridge a little more efficient
    Volvo Farmer wrote: »
    It would take a lot of experimentation, with removing the evaporator cover from time to time to check frost build up, but in some circumstances, I think efficiency could be improved in this manner. Defrost systems are typically designed for worst case scenarios, moist environment, etc, and I believe there is room for improvement if your set of circumstances is better than worst case.

    I would try putting some sort of temperature sensor on the evaporator coil to see whether that would give me an idea of whether it is ice covered or not. I expect that the temperature of the coil would get a lot lower while the compressor is running compared to the freezer temperature once ice started to build up. You could either use this just to gather data or you could try using it to trigger a defrost cycle. (Sounds like a job for an arduino.)
    SMA SB 3000, old BP panels.
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