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Thread: Chest freezer as a chest refrigerator

  1. #1
    Jay Guest

    Default Chest freezer as a chest refrigerator

    I came across this on another list. A clever guy in Austrailia has converted a chest freezer to a chest refrigerator and it only consumes 100 watt hours per day. It all makes sense.

    Here is the link.

    http://www.builditsolar.com/Projects...est_fridge.pdf

    I have been very seriously considering replacing my frig but I may give this a go instead.

    Jay

    PS: The original link is apparently dead:

    Quote Originally Posted by ILFE View Post
    Bill, the link for the write up in the first post of that thread is no longer valid.

    I found it here, though: http://mtbest.net/chest_fridge_1.pdf

    Perhaps, one of you staff folks may change it in that post?
    Thank you ILFE. -Bill 3/25/2014
    Last edited by BB.; March 25th, 2014 at 7:30 PDT.

  2. #2
    Join Date
    Jun 2003
    Location
    pittsburgh, pa
    Posts
    10,262

    Default Re: Chest freezer as a chest refrigerator

    jay,
    that was interesting and it does make you wonder about refrigs today. the biggest problem i could see doing this is fitting it where the refrig used to be. that's not much space for it as most kitchens are designed to allow only a small section for it.
    niel
    NIEL

  3. #3
    Tad Guest

    Default Re: Chest freezer as a chest refrigerator

    That was great to read. We have two propane-powered upright refrigerators and one chest-type propane freezer at a cabin. I can certainly attest to the fact that the freezer has absolutely no trouble coping with the hottest days, while the freezers on the two refrigerators struggle mightily.

    We're going to remodel our kitchen at our house one of these days...I wonder how my wife would feel about a chest refrigerator? As Niel notes, they eat up a lot more floor space.

    --Tad

  4. #4

    Default Re: Chest freezer as a chest refrigerator

    Interesting idea, but hardly novel. For example, Danzer makes an 8 cf DC chest fridge, but, at ~$1,000, it’s not cheap. See: http://www.backwoodssolar.com/Catalo.../refriger2.htm

    Note that the Vestfrost SE255 freezer described in the article is a 9 cf unit (= 255 liters). That’s pretty small by U.S. standards. I have to admit that I question the author’s energy numbers and environment (103 Wh/day at ~ 18 C, or ~64 F, which is rather cool). That’s ~ 28% less than the Danzer’s 70 F requirement, and it probably doesn’t include inverter losses.

    Nonetheless, it’s a nifty idea, and converting a “standard” chest freezer may be worthwhile. However, the interior may need a small circulation fan (= higher energy consumption) to avoid stratifying interior temperature layers.

    HTH,
    Jim / crewzer
    120618: System off-line for a while...

  5. #5
    mparmer Guest

    Default Re: Chest freezer as a chest refrigerator

    Here are 2 thermostats specifically meant for controlling the temperature of chest freezers, with a different outcome in mind: creating the right temperature for beer and wine. It would serve the same purpose, though, to convert a freezer to refrigerator temperature.

    http://ceisites.com/9025.html
    http://www.morebeer.com/product.html?product_id=16663

  6. #6
    Wayne from NS Guest

    Default Re: Chest freezer as a chest refrigerator

    :? I too question the author’s energy numbers. Two minutes of run time would hardly be enough for the system build up pressure, let alone do any cooling of the interior, and 90 seconds? come on - - .
    I agree that it should be much more efficient than a "normal" refer, but his numbers and run times are pure bull **** The only way his thermostat (if not defective) could possibly shut down the compressor that quickly would be if the thermistor happened to be glued to the interior wall, right over the evaporator nozzel and that would give no indication of the interior tempature at all!
    Not putting down the whole idea, just offering a reality check.
    Would be great if someone else could try it and report proper numbers and tempatures after a bit of experience.
    Just a note on adding a length of wire to between the thermostat and it's thermister sensor: It may well be sensitive to rhe length of wire. Have run into this with indoor-outdoor electronic thermometers and it doesn't seem to have so much to do with wire resistance, but more a capacitance thing. To save energy and avoid heating the thermistor, the circuts usually only check the temp every minute or two, by sending out a HF AC pulse. So, confirm operation after any modification.
    Wayne

  7. #7
    Wayne from NS Guest

    Default Re: Chest freezer as a chest refrigerator

    Thought more about this today - when I was “working”.
    The following numbers are rounded off and do not take into consideration the inverter losses etc.
    One chest freezer listed as using 274 kWh per yr, average temp 0F inside and 70F room temp.
    Since energy consumption is directly related to temp differential across the walls of the freezer, (inside to outside) it follows that energy consumption would be 274KWH / 70F= 3.9 KWH per yr, per degree F difference.
    It follows that when using the freezer as a “chest refer”, a good inside temp would be 35F, which would result in a 35F differential across the walls.
    35X3.9=135.5KWH per yr. Just half the energy consumption and that makes sense.
    Per day consumption would be 135.5/365=.37KWH, or 370watt hours/12Volts=31AH per day at 12 Volts. NOT BAD!! One could easily install a small brushless 12VDC fan such as used in computers etc and run it at reduced speed and power to prevent stratification of internal temps. Easily less than 1 watt. No need for a hurricane inside, just a very little air movement.
    I think this is very interesting and very doable.
    If someone has a chance to try this before I do, please let us know the real world results.
    Thanks
    Wayne

  8. #8

    Default Re: Chest freezer as a chest refrigerator

    the reason a chest unit is more efficient is because the cold air sinks.
    not as much loss as an upright unit where you lose a bunch each time the door is opened.

  9. #9
    Jay Guest

    Default Re: Chest freezer as a chest refrigerator

    Thanks for all the feedback!

    I agree, the numbers don't add up in a number of ways.

    If you take the link that Crewser sent (I look at Backwoods all the time. Can't believe I missed chest refrigerator there) it seems that the Sundazer 'frig' uses 27 percent less electricity than the identical freezer. Given that, then a Kenmore 7.2 cu ft freezer that normally uses about 274 kWh/yr would use .2 kWh/day. Double the Aussies numbers but still very descent.

    BUT If one gives up the top freezer refrigerator then one has to buy a chest freezer to replace the top freezer. I looked at a 5 cu ft Kenmore chest freezer and it uses .67 kWh/day. Add the two together and now you are back to almost a kWh per day (.87 kWh/day) for only 12 cu ft of cool/cold space.

    My 12 year old 21.5 cu ft Amana uses about 1.3 kWh/day with the temp set at the warmest settings. It doesn't add up. A new Kenmore 15 cu ft top freezer refrigerastor uses 1.0 kWh/day. I t seems then that most of the energy used is to keep the freezer cold, than to cool food.

    Maybe a freezer is more an electical luxury that I realized. Maybe I need to look at not having a freezer. hmmmmmmmmmm.

    Thanks,

    Jay

  10. #10
    Join Date
    Feb 2003
    Location
    Green Bay, WI
    Posts
    591

    Default Re: Chest freezer as a chest refrigerator

    Maybe I am wrong, but isn't it more then a 2 to 1 gain halfing the temp? I mean the regular chest freezer is say 70 degrees different at 35 degrees different wouldn't it work about 1/4 as much or more realistically 1/3 as much? It seems to me when I push my chest freezer temp way down (-15F) it runs proportionally longer.

    What is the temp drop on the evaporator from ambient? Maybe as you approach that it isn’t a flat ratio?
    XW6048, 4 KC 120's, 4 KC 130's and 4 Evergreen 200's totaling 1800w of PV, MX-60 charge controller, Trimetric meter and eight AGM 8A8D's or 490 amps at 48v. 4 tons of geothermal and 3 tons of air source.

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