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Size of inverter to start a refrigerator?

Discussion in 'Home Power and Microgeneration' started by Roger Moss, Apr 20, 2006.

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  1. Roger Moss

    Roger Moss Guest

    I want to get an inverter to run my refrigerator. It is a normal size
    (850*600*600mm), "A" efficiency refrigerator. The running power is pretty
    small - 70W I think - but I'm not sure how much current is needed to start
    up the induction motor in it.

    Will a 250W inverter get it started, or do I need something bigger?


  2. John Smith

    John Smith Guest

    Once you get it started off an inverter check the servo motor for the defrost
    timer. They are power picky and it may not run at all.
  3. Vaughn Simon

    Vaughn Simon Guest

    I would be very surprised if it would start on that little inverter.
    Refrigerators can easily take up to 10X their run power for starting. You did
    not mention what type of inverter, many refrigerators do not seem to like square
    wave power (or MSW). My 'fridge (about 200 watts run power) will not start on
    my little 600-watt Honda "lunch box" genny, and it will not start reliably on my
    1000-watt inverter, but does run very well on my 2000-watt Honda inverter genny.

  4. JoeSP

    JoeSP Guest

    This and many other similar postings points to the necessity for a
    demand-surge capacitor bank. A very common problem with alternate power is
    the need for a much higher load for a brief period of time for things like
    starting motors.

    I'm not aware of any such devices on the market, but I'm sure a good
    engineer could enlighten us.
  5. Dave Nay

    Dave Nay Guest

    The problem there is that capacitors are a DC device, and actually will
    filter AC. For a capacitor bank to be of any use, it needs to be on the
    DC side of an inverter, and therefore still limited by the capacity of
    the inverter.
  6. JoeSP

    JoeSP Guest

    And therein lies the engineering challenge.
  7. surfnturf

    surfnturf Guest

    Joh, thanks for the kick starter tip. May want this some time in the future
    for some larger drives in my future full sized application.

    Agree that fridge should start with small inverter for the OP. Just need to
    use decently sized wiring and securely connect inverter to battery. Then the
    battery is the "capacitor" and most inverters will handle the temporary
    surge. Of course, better inverters will handle more for longer.

  8. Eric Sears

    Eric Sears Guest

    Thanks for your comments Harry.
    I wonder if you could further comment on these questions:

    Does the Trace send a pulse about every second - which clicks a relay
    in the fridge on/off? (I'm not talking about the normal clicking
    associated with turning the motor on/off at the usual intervals)

    Does the inverter shut down or go into "standby" mode at intervals
    when the motor is not running?

    What make is the fridge?

    Does it seem to have electronics which run all the time (things such
    as timers, fan etc).

    Generally the small "dorm" type fridges are no problem because they
    are just a compressor with a thermostat.

    Any further comments appreciated.

    (PS - the "super-effficient" fridge I have just remembered is a Gram)

    Eric Sears.
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