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Thread: Running a fridge

  1. #1
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    Default Running a fridge

    Hey guys,
    If i have 30 amps in 6 x 12V 5A solar panels wired in parallel running to a 500w inverter rated at 65 amps, can i plug a 240V fridge that consumes 110W straight into the inverter without a battery, and allow the fridge to turn on when its sunny enough and off when its cloudy or dark ie as the inverter has enough power from the panels to power the fridge, so acting as a switch i guess.
    Thanks
    Wheelz

  2. #2
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    NO you cant just run an inverter from the solar panels as the voltage of 12v panels will greatly exceed the input voltage of the inverter (usual cuttoff 15v).That is the usual case
    Your problem its impossible to do what you want with a standard 240 v refrigerator as you have 6x12v x5 a panels thats only 360w no where near enough to start the refrigerator..You will need about 1000 w to start the fridge.
    older refrigerators can be modified to run off inverters as small as 300w . But from limited information I have the very latest type ones cannot be modified in the same way,
    Some people that know nothing about refrigerator motors will tell you that a fridge motor will use same amount of power to start up if under load or not under load because of the motor design ,, Its not true

  3. #3
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    Really? 1000W to fire up a fridge rated at 110W? I know they surge on startup but that much?
    Even if my 12V panels are in parallel you think there will be too much voltage ? I know they fluctuate depending on conditions but i didnt think they would break 15V each...Righto i will take your advice on board. Cheers
    Wheelz

  4. #4
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    You will find even some 1000 w inverters wont start a reasonable sized fridge reliably;
    Low frequency ones certainly will but they are about double the price of high frequency ones
    12v panels should easily exceed 15v or how could they fully charge a 12 v battery to 14.4v ?? charge controler losses will account for some voltage drop also
    but your main problem is at best you have 360w..

  5. #5
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    I see. As this is a beginners thread i will throw out some beginners like questions
    The 500w inverter Im looking at offeres 1000w surge, and is rated at 65A max input.
    If this inverter was running of a battery as intended and not a solar setup, the max voltage supplied would be 14.4V ?
    14.4v x 65A max = 936W. How can 1000w surges be compensated for?
    Sorry, probably a real beginners question.
    Thanks John.
    Wheelz

  6. #6
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    that 936 w is the theoretical max but you will never get that under any condition.
    for a start the inverter is most likely to be about at best 90% effecient = 840w
    connector losses about 40w =800w
    you will only get 14.4v if the battery is under charge a battery at rest will only give a little over 13v
    that 1000w surge will only last for a few milliseconds in most cases

  7. #7
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    Do they make refrigerators that are built to run off solar power? Or as far as modifying an older fridge, how old does it have to be? Do you know of any popular models that are good for modifying that also have a refrigerator water filter? I've got an old refrigerator in my garage that I wanted to tinker with and see if I could power it with solar panels and batteries.
    Last edited by DeniseT; 03-05-2012 at 08:23 PM. Reason: .

  8. #8
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    Quote Originally Posted by DeniseT View Post
    Do they make refrigerators that are built to run off solar power?
    Yes but the question is can you afford one, plus the equipment to run it. If you have commercial power it would be foolish to run one off of solar alone.

    Sun Dancer
    Norcold
    Tundra


    Here is a decent article written by a friend of mine. Backwoods Magazine it very biased to the point of radical survivalist, but Jeff is honest and knows his stuff.
    MSEE, PE

  9. #9
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    Quote Originally Posted by DeniseT View Post
    Do they make refrigerators that are built to run off solar power? Or as far as modifying an older fridge, how old does it have to be? Do you know of any popular models that are good for modifying? I've got an old refrigerator in my garage that I wanted to tinker with and see if I could power it with solar panels and batteries.
    The old fridge in the garage is usually a real energy hog.

  10. #10
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    I've mentioned in a couple of threads on this forum about a great conversion project for a fridge in the garage. I converted an old chest freezer that I purchased for $40 used and a digital thermostat I got off of ebay for less than $20. It uses on average a little less than 190 wh per day. Very easy to run on solar, of which I do.

    These are a couple of links to the references I used to blueprint my DIY project off of. They are not advertisements, so I hope they don't get deleted by the mods, as I think that they offer good information for people interested in doing the same.


    http://www.ehow.com/how_5684552_conv...rigerator.html

    http://lifehacker.com/5334245/conver...t-refrigerator

    After looking at a couple of the articles, it gets kind of redundant. The premise is the same, and the controller is a variant of the same thing as well.

    Here is a YouTube video of the same idea.

    http://www.youtube.com/watch?v=ISJLyHK457I

    http://www.youtube.com/watch?v=2UeuO2x7xgU


    Again, this is one of the best projects I have done with my DIY solar panels. My converted freezer to fridge uses on average less than190 watt hours a day, and I have over 15 cu ft of fridge in my garage!

    Good luck in your endeavours.

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