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  1. #1
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    Sep 2017
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    Overcharged LG ductless minisplit - multizone system

    Hi,

    I have an LG LMU480HV condenser that is hooked up to 8 indoor minisplit units. The two upstairs units keep cycling on and off every 1-2 minutes when any of the other units are actively heating and not in idle mode. This does not happen during cooling mode because the fans stay on in that particular mode.

    After some troubleshooting with my contractor and LG techs, I think the problem was an overcharge of the system. From what I've seen and heard, it's harder to correctly charge a system like mine since the piping runs are so long and they go to so many different units.

    In any case, the original charge when the unit was turned on was 15.9 lbs. The contractor came back and took out 3 lbs., which left 12.9 lbs. This definitely lowered my amperage draw and kwh usage by 30-40%. However, the short cycling continues for my upstairs units. LG techs did a line length and charge analysis and said that I really needed 12.56 lbs. So that's 5.44 ounces that I need to take out. The contractor is coming out to take out some more, but I wanted to know how much a difference 5 ounces makes in these newer inverter compressors. I've heard they need to be dialed in pretty accurately.

    Could I ask my contractor to start at 12 lbs. and see how the system works and then add more if he needs to?

    Thanks for any information.

  2. #2
    Join Date
    Aug 2002
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    Southold, NY
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    If LG wants 12.56 then pull the entire charge and weigh in 12.56.

  3. Likes ksefan, kdean1 liked this post
  4. #3
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    If LG wants 12.56 then pull the entire charge and weigh in 12.56.
    We will do that. But the LG calculation is based on the contractor's line length calculations and that might be off by a few feet here or there.

  5. #4
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    Aug 2002
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    So
    What does the contractor advise?

  6. #5
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    Sep 2017
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    Thread Starter
    Not sure. I guess I have to trust his line calculations, but I am wary because of how much he overcharged the system originally.

    That's why I'm thinking to start at 12 lbs first and slowly work our way up. But I'm not sure how big of a difference 5 ounces has on a system like mine. Maybe starting at 12.56 lbs. and bleeding out is easier if the system still runs hot and is short cycling?

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