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  1. #1
    Join Date
    Feb 2004
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    Midwest
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    9,932
    I think I'm going into one of those brain freeze modes again.

    Just put a spare fridge in the garage and it's hotter than hell out there, so it runs a lot.

    I'm not going to put too much in it and it's a 21 cu ft, so I thought I'd reduce the load by putting boxes or something in it.

    The question I've got, is whether it's a refrigerator or a building a/c, which is less load, a box with nothing in it, or a solid square object of the same size? In the latter case, what would be the most efficient material for the solid square object to be made of?



  2. #2
    Wouldn't matter, really. For the frig you could put a cardboard box or a load of CMU in it - it won't care, and the only thing you'll have to worry about is cooling the air that gets exchanged with the air in your garage. I wouldn't put anything in it, as it will have to overcome whatever heat the object has, running your electricity that much more to cool the object down.

    To help that frig in the summer try to lower the heat in the garage somehow. You could put a little exhaust fan with a temperature sensor if you want to go through the trouble, but I wouldn't bother as long as it doesn't get too hot nor have direct sunlight warming the thing up.

    For a building, the same principles work. Whether an office building is full or not has little effect on the total load (that is unless it's full of computers and other heat-producing equipment). What matters more is how much infiltration, interior and exterior heat load the system will have to deal with.

    For the frig and the building, if the system is turned off, the objects will keep their temperature longer if there is more mass, whether full of beer bottles or furniture. This 'heat inertia' needs to be overcome once the system starts up again, which is why larger buildings take a while to cool down on a Monday morning after being shut down the entire weekend.

    Wow, too much coffee this AM. Hope all that typing gets my point across.

  3. #3

    Lightbulb an alternate point of view...

    If the upright cooler (ref or freezer) is empty, every time you open the door, most the cold air runs out the bottom. If you keep the cooler full of empty boxes a lot less cold air runs out the bottom when you open the door. It is to your advantage to keep the cold air in the empty boxes. This concept is of little or no value when applied to a chest cooler or freezer.

    Fred

  4. #4
    Join Date
    May 2000
    Location
    Colorado flatland native
    Posts
    15,067

    Why don't you get a smaller fridge?

    Fill it with chunks of 2" foam.
    My doctor gave me six months to live, but when I couldn't pay the bill he gave me six months more.
    Walter Matthau

  5. #5
    Join Date
    Oct 2002
    Location
    Yo.... Here!, I'm right here..
    Posts
    6,236
    I had a box with nothing in it once, I divorced her.

  6. #6
    Join Date
    Oct 2002
    Location
    Yo.... Here!, I'm right here..
    Posts
    6,236
    Originally posted by pjs
    I had a box with nothing in it once, I divorced her.
    whoops wrong thread I thought this was sex therapy

  7. #7

    Re: an alternate point of view...

    Originally posted by ice machine undertaker
    If the upright cooler (ref or freezer) is empty, every time you open the door, most the cold air runs out the bottom. If you keep the cooler full of empty boxes a lot less cold air runs out the bottom when you open the door. It is to your advantage to keep the cold air in the empty boxes. This concept is of little or no value when applied to a chest cooler or freezer.

    Fred

    I agree.

    Hey Undertaker, I need a source of used ice makers to re-sell. Any leads for a guy in Central Texas?

  8. #8
    Join Date
    Feb 2004
    Location
    Midwest
    Posts
    9,932
    I'm doing a little experiment. I put 4 almost empty 30 lb cans of R22 in the refrigerator compartment and am monitoring the cycle time with a recording graph. I must admit the first cycle took *forever*, probably because the cans were at 85 degrees



  9. #9
    Join Date
    May 2001
    Location
    Bennington, Vermont U.S.A.
    Posts
    13,864
    This is the definition that I got for refrigeration way back when.

    "The controlled removal of some heat from a confined space."

    Trying to follow your thought process--you are saying that if you reduce the 'confined space' you are controlling the 'the removal' of heat. IMHO I don't think so.

    The biggest load on your test refrigerator is transmission of the heat through the insulation and leakage of air around the door seal. When you open the door and close it again some of the heat will be absorbed into the cyclinders but ultimately that heat will be given up to the refrigeration system. You are putting something into the confined space you are reducing the confined space. How if you cut a big block of syrofoam and packed it into the refrigerator then you would be reducing the confined space and your load would go down.

    [Edited by benncool on 07-23-2004 at 09:58 AM]

  10. #10
    Join Date
    May 2002
    Location
    Colorado
    Posts
    697
    I think you will find that an empty fridge will cycle more often than one that is filled with thermal mass. But the total run time won't be much more.

  11. #11
    Join Date
    Feb 2004
    Location
    Midwest
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    It pretty much turned out the way common sense would dictate:

    Cycle times over several cycles:

    Nothing in it: 1.8 hours per cycle
    4 almost empty 30# R22 cylinders: 2.1 hours per cycle
    Empty styrofoam beer cooler with lid: 1.5 hours per cycle

  12. #12
    Join Date
    May 2001
    Location
    Bennington, Vermont U.S.A.
    Posts
    13,864
    Originally posted by midhvac
    It pretty much turned out the way common sense would dictate:

    Cycle times over several cycles:

    Nothing in it: 1.8 hours per cycle
    4 almost empty 30# R22 cylinders: 2.1 hours per cycle
    Empty styrofoam beer cooler with lid: 1.5 hours per cycle
    Hopefully, mid, you have a recording ampprobe or else you are going to be accused of not having a life.

  13. #13
    Join Date
    Oct 2003
    Posts
    566

    Wink

    At least fill it with something worthwhile, like a keg. I have a second fridge as well and keep a keg all the time with a draft handle drilled through on the outside. Nothing quite like draft beer and you can't beat the cost...
    Hey mosquito, quit biting (slap!!) me...
    Anyone like Josey Wales?
    C'mon, you know I'm right!

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