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Most efficient refrigerator

Discussion in 'Home Power and Microgeneration' started by m Ransley, Jan 25, 2004.

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  1. m Ransley

    m Ransley Guest

    Sun Frost is advertised as the most efficient refrigerator . The RF19
    model consuming 770 watt per day at 70 degree or 281 KWH yearly.
    I purchased a Sears Kenmore model 61982 18.8 cu ft . Gov rating on
    consumption is 417 KWH yearly.
    Well i covered it with 1 " r 7.2 foamboard and recessed it. my
    last 10 day KWH use was 560 watt per day or 204 KWH yearly, measured
    with a Kill-A -Watt.
    Now im at 69 degree , single , But cook all food. I Beleive the KWH
    Gov rating is to replicate a family and yearly temperature swings,
    so when its warm it will consume more in its ratings. The Sun Frost has
    a much higher 90 degree consumption quote of 1.09 KWH daily or 398
    KWH yearly, And is this reflective of a familys use ? I dont think
    So who makes the most Efficient refrigerator?? Yes, Sears is better
    than most people think.
    I feel its underated and less than 1/2 the cost.
    And Sears delivers free, { sometimes }
  2. Nick Pine

    Nick Pine Guest

    Nonono. Energy units are watt-HOURS per day.

  3. m Ransley

    m Ransley Guest

    I know you are thinking , well he insulated it. Yes , not the back yet
    , and 2 more inches will go on for r 21.6
    The point is anyone can do this, insulate it better and recess it .
    making even better than my present KWH costs. And the initial cost of
    the Sears is acceptable, as I feel the Sun Frost is not. Payback
    period for a Sunfrost ? What payback !
  4. m Ransley

    m Ransley Guest

    Nick ,Who uses energy units Where are they displayed for anything. I
    have never heard of that term
  5. m Ransley

    m Ransley Guest

    OK nick you are right, I printed it wrong, but I beleive my numbers
    and theory are correct
  6. Up until the early 1990s, sunfrost had a major edge. Around that time tere was
    a competition for the most energy efficient model refrigerator with a large
    cash prize, and the major manufacturers got on board the efficiency bandwagon.
    We recently bought a 25 cu ft refrigerator from sears that uses about 1/2 (or
    less) the energy of our old 19 cu ft model.

    Using foamboard can be counterproductive on some refrigerators, the smaller
    units especially place the condensing coils just under the surface of the
    sideas and top and depend on airflow over them to carry away the excess heat.
  7. Bob Peterson

    Bob Peterson Guest

    IIRC, the cheap fridge I bought was listed as using something like $60 a
    year worth of electricity, so that would be like 600 kwh per year. The next
    step up in efficiency would have saved about $20 a year in electricity but
    cost something like $300 more. Not much of a bargain IMO, unless you are on
    very expesnive electricity.
  8. Ecnerwal

    Ecnerwal Guest

    I'm fairly negatively impressed that even the "new, more efficient"
    regiferators of recent years still have the most inefficent placement of
    the compressor and coils (hot parts). This was done efficently in the
    1930's - hot parts on top, cold down below, arranged for excellent
    airflow through the hot coils.

    Now you have a hot compressor underneath a cold fridge, and the coils
    either behind or (worse yet) wrapped all around the outside under the
    skin (so no additional insulation an be added). Thus, bottom freezer
    models are more inefficient becasue the freezer (coldest) is placed near
    the compressor (hottest).
  9. East-of-lake

    East-of-lake Guest

    So I should look for a used commercial frig that has the compressor on top?
    Haven't looked at them before but (from my days in the restaurant biz) as I
    remember it many of them do have the exaust grill on top and storage all the
    way to the bottom so they must be mounting the "hot" parts on top.
  10. This is one of the touted advantages of the SunFrost models, the
    compressor is on top. Also, lots of insulation, a lower-powered
    compressor (higher efficiency, but takes longer to cool down) and DC
    options to eliminate inverter efficiency losses. Significantly higher
    prices though...
  11. Ecnerwal

    Ecnerwal Guest

    Depends. If the unit is new enough to have a newer type, more efficienct
    compressor, perhaps yes. An older one might lose enough efficiency in
    the compessor end to fail to make up for good thermal design in
    placement of parts. Hard to know for sure, since I suspect that
    commercial units are probably exempt from the sort of energy labeling
    that consumer units have had for the past several years. Then again,
    they are generally built so that you could replace the compressor. All
    the free-stanging commercial units I've met would want a lot more
    insulation - only walk-ins seem to get heavy insulation.

    I've often wondered if it might not be more efficient to put in a very
    well insulated walk-in (with the compressor unit located outdoors). On
    the one hand, it's large, but on the other hand, there's no problem
    insulating the living heck out of it.
  12. m Ransley

    m Ransley Guest

    I agree they could get more efficiency with a top coil- compressor .
    But the unit i have is rated the most efficient at Energy Star. I saw
    a few top coil recessed models with low yearly KWH costs , Maybe Sub
    Zero. But they were the nice expensive ones.
  13. wmbjk

    wmbjk Guest

    It would seem that room temperature air flooded over the hot parts would
    be only somewhat warmer, and that extra heat could be easily compensated
    for with a little extra insulation. Then the works can be on the bottom,
    which is practical since that space would otherwise be closer to the
    floor than is desirable for shelving. Sunfrost claims there's an
    efficiency advantage to top mounting, it's probably little more than
    marketing hype.

  14. Guest

    Air near the floor tends to be cooler, and hot coils with a chimney above
    could have more natural airflow. Sunfrosts have "thermal accumulators,"
    refrigerant heat stores to allow the hot side to cool even when the
    compressor isn't running, an idea from the 30s that's disappeared from
    most modern fridges.

  15. Q

    Q Guest

    Wouldn't a chest design be more efficient than a standard upright design? I
    know it wouldn't sell because of current kitchen design.

  16. John Hall

    John Hall Guest

    I think you missed the point that I think he was intending to make...
    other things being equal, a chest design is more efficient because it
    does not spill the cold air on the floor when opened. The falling cold
    air is replaced by warm room air, which then has to be cooled when the
    door is closed.
  17. Hmmm, the mass of the air would be one factor and the humidity would be the
    other. Of the two, I'm guessing the high humidity would be more important,
    since the humidity has to be condensed into liquid, which could require
    significantly more energy.
  18. John Hall

    John Hall Guest

    Where I live "we don't have humidity", but I see your point.
    It just makes the case stronger.
  19. daestrom

    daestrom Guest

    True. And a 'full' unit has less free air to 'spill'. Which is why a unit
    that is full or nearly so runs more economically than an empty.

  20. Guest

    OTOH, it has more surface to instantly condense water vapor
    from room air with a 50 F dewpoint when the door is open.

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