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Community and Q&A

Why are refrigerator coils not mounted outside of our homes?

jane84 | Posted in General Questions on

Wouldn’t it be more efficient to exhaust hot air outside in summer like an air conditioner? And in winter why isn’t cold air from the outside used to maintain fridge and freezer temperatures? Thanks!

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  1. GBA Editor
    Martin Holladay | | #1

    A few refrigerator manufacturers have come out with models that have an exterior coil. (Such a setup is standard for commercial walk-in refrigerators.)

    Sunfrost, a small California manufacturer of extremely efficient refrigerators designed for off-grid use, used to make a 12-volt DC refrigerator with an exterior refrigerant coil that operated on the thermosyphon principle. Back in the late 1980s, they sold it to off-grid homeowners in cold climates, and my friend Bill Gessner bought one. It's still working more than 20 years after he bought it.

    Sunfrost no longer offers the option, because it had control issues. When the thermometer drops to -20 degrees F, the back of the refrigerator would freeze.

    At my own house, I installed my Sunfrost refrigerator in an exterior wall. The door of the refrigerator extends into my kitchen, but most of the rest of the refrigerator is in my unheated mudroom. The refrigerator coils are in a cold environment, increasing the unit's efficiency.

    There are pluses and minuses with this arrangement. While having the coils "outdoors" increases the efficiency of the refrigerator, my house doesn't gain any benefit from the waste heat given off by the refrigerator -- a valuable benefit in Vermont, where we need space heat for 8 months of the year. (Actually, it's handy to have just a little bit of heat in my mudroom, but that's another story.)

    If you want, you can experiment with designing a homemade refrigerator with an outdoor air duct and a fan -- one that uses winter air to keep your groceries cold. You will probably discover, as hundreds of tinkerers before you already have, that there are two problems: finding motorized dampers that seal tightly enough to prevent air leaks, and preventing your lettuce from freezing when the outdoor air is below zero.

    The standard method of taking advantage of winter temperatures for food storage is to cut ice from your pond during the winter, and to stack the blocks of ice in a walk-in insulated cold room. Or you can simple create an unheated cellar under your house. My cellar stays at 33 degrees for half the year.

  2. user-963341 | | #2

    In the commercial world economizers are gaining a fair amount of acceptance. I see them in large coolers in convenience stores all the time. The banks of reach in coolers and similar large cooler boxes are prime uses.
    They use a differential temperature sensor/controller to turn the compressor off and activate a fan to bring cold air into the box. Typically this happens at about 20F outside temperature. Because freezers require much colder temps and the typical number of hours those temps occur is low I've never seen a freezer application.
    Residential refrigerators are much smaller and more efficient than commercial units, so the initial cost is prohibitive. Also, we throw the whole unit away on the residential side. In commercial units the box often stays through a few refrigeration unit replacements.
    That said, I'm currently looking to make a simple system to control the temperature in my to be built root cellar in my to warm basement.

  3. chuck77 | | #3

    Along a similar line I've wondered why refrigerators could not be used to assist with our water heating. Martin?

  4. GBA Editor
    Martin Holladay | | #4

    The question has been discussed several times on GBA. Here are two links:

    Heat pump water heater + refrigerator combo, someone?

    Using heat from fridge to heat water?

  5. Expert Member

    Jane. Several of the larger home builders around me have gone back to using an older solution and include an insulated pantry in their kitchen designs with a vent to the outdoors.
    I'll leave it to Martin, Dana et al. to decide where best to place the place the air and vapour barriers in that situation :)

  6. jinmtvt | | #6

    In cold climates, refridgerator is not a big waste if you ask me.
    Also, the most efficient ( cheap and labor ) way to use outdoor temps to help with fridge enerty use during winter time is to ice up some kind of container outside and let it grab energy from the hotter
    ( or release its cold as u wish to term it ) refridgerator . It does take some space, but you can also use a sealed cabinet outside to store froozen items for free which then leaves more space for your "exchangeable" ( keep 2 to itnerchange ) water bucket .
    Of course it doesn't help at all during summer or in hot climates.

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