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  1. #1

    Hermetic Compressors

    I understand if an A/C system has a leak and has been "topped off" more than once, you may need to replenish the oil in the compressor.
    I understand how to inject the oil but is there a way or a test i can do to find out how much oil it may need?
    Thanks

  2. #2
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    Quote Originally Posted by KlingerService View Post
    I understand if an A/C system has a leak and has been "topped off" more than once, you may need to replenish the oil in the compressor.
    I understand how to inject the oil but is there a way or a test i can do to find out how much oil it may need?
    Thanks
    No. Short of removing the compressor and dumping the oil there is not way to tell in a hermetic system. This is one issue i think is neglected a lot in our field. Some scrolls and other herms. do have a sight glass for oil. I hope the whole field goes that way. I have seen small splits with herms. completely out of gas and you ask "What will you do about oil"? Uless one of the old timers has someway of knowing then i would like to learn it as well. I asked the instructor at the Coplend class, And he said when you replace a herm. you should take the oil charge, and subtract that by what you get out of the bad compressor, And take that much out of the new compressor. But i wonder how much you lose in the recovery process or by leaks etc.

  3. #3
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    If any oil gets out, you will see it's trail. If it looses all the refrigerant slowly it still may not need any oil. Depends on where the leak is. If you see a large oily area such as when an accumulator rusts out, you may want to add a little.

  4. #4
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    Average resi system, is about 4 ozs of oil removed during recovery.

    If your losing oil from a leak, you should be able to find and fix the leak pretty easiy then, and not lose anymore oil.

    Unless its a big leak, your not losing that much oil.
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  5. #5
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    Yea its hard to determine how much oil is lost in any system . Problem is , if you add too much oil its bad , and if theres too little its bad .

    I do know if you add too much ... both low and high sides will read higher than normal , and it wont cool worth a hoot .

  6. #6

    Thanks

    Thanks to everyone who replied to my question.

  7. #7
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    If you've had a major leak, particularly on the low side, it's not a bad idea to change the oil in the compressor anyway. The oil, particularly POE, sucks up moisture like a sponge.
    The oil goes acidic and attacks the insulation on the motor windings and the moisture can freeze in the expansion device.
    I know it's not convenient to change the oil in a hermetic, but some times it's the only way to go if you don't want to have to explain to your valued customer why you're replacing his compressor and/or he had to throw out a grands worth of stock.
    New drier, new oil charge.
    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

  8. #8
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    Quote Originally Posted by Slatts View Post
    If you've had a major leak, particularly on the low side, it's not a bad idea to change the oil in the compressor anyway. The oil, particularly POE, sucks up moisture like a sponge.
    The oil goes acidic and attacks the insulation on the motor windings and the moisture can freeze in the expansion device.
    Oil change is not needed. You can't drain all the oil out of the compressor to begin with. So you would still have moisture in the oil.
    Filter driers will take care of the moisture.
    I've done repairs on R410A HP that the vapor line was punctured by a nail. And open to air for 3 months. Vacuum, and 2 LLFD changes. No moisture left in system, and no acid. Running 4 years now.
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  9. #9
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    Quote Originally Posted by beenthere View Post
    Oil change is not needed. You can't drain all the oil out of the compressor to begin with. So you would still have moisture in the oil.
    Filter driers will take care of the moisture.
    I've done repairs on R410A HP that the vapor line was punctured by a nail. And open to air for 3 months. Vacuum, and 2 LLFD changes. No moisture left in system, and no acid. Running 4 years now.
    I'd still advise replacing the oil. It's not as much of an issue with A/C but when you go to low temp moisture can be a real pain.
    Selection of the correct type of drier seems to be important to
    Last edited by Slatts; 06-14-2008 at 02:13 AM. Reason: more info
    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

  10. #10
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    Don't confuse low temp(under-20°F as far as I'm concerned) with A/C.
    (Cascade systems are a field in themselves.)
    If There is moisture in a system that runs -20, say a R404A with POE oil, filter driers still remove the moisture.
    Could some make it by the filter drier and freeze in the metering device, sure could and has. And was probabaly in the vap while you were vacuuming, not in the compressor.
    There is no way your going to remove all the moisture from a system with a vac pump when its evap is in a -20*F enviroment. And dumpimg the oil out of the comp isn't going to get all of it out of the comp either, if there is any in the comps oil.

    There are times to dump the oil.
    But as a general routine practice, your only fooling yourself, and wasting time and money.
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  11. #11
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    Quote Originally Posted by beenthere View Post
    Don't confuse low temp(under-20F as far as I'm concerned) with A/C.
    (Cascade systems are a field in themselves.)
    If There is moisture in a system that runs -20, say a R404A with POE oil, filter driers still remove the moisture.
    Could some make it by the filter drier and freeze in the metering device, sure could and has. And was probabaly in the vap while you were vacuuming, not in the compressor.
    There is no way your going to remove all the moisture from a system with a vac pump when its evap is in a -20*F enviroment. And dumpimg the oil out of the comp isn't going to get all of it out of the comp either, if there is any in the comps oil.

    There are times to dump the oil.
    But as a general routine practice, your only fooling yourself, and wasting time and money.
    Moisture is absorbed by the oil then pumped round the system in the oil with the refrigerant.
    It doesn't take long for the moisture to be evenly distributed in the oil. by replacing the oil in the compressor (the largest concentration of oil in the system) You're diluting the moisture by a pretty high percentage. That and drier replacement and a good vac will, on most jobs, stop ongoing moisture problems.
    Confession time: i don't always replace the oil myself unless I suspect the system's been open for some time or is very wet. like a rusted out suction accumulator on a system that may have run down on a vacuum.
    It's much more likely to be changed on a compressor with service valves and rota locks.
    Done that
    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

  12. #12
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    Quote Originally Posted by Slatts View Post
    If you've had a major leak, particularly on the low side, it's not a bad idea to change the oil in the compressor anyway.I know it's not convenient to change the oil in a hermetic

    i dont think about it being inconvenient, but if you have a big leak and lost "a bunch" of oil

    let's assume you know the factory oil charge

    how do you account for the oil lost on the leak, versus the oil accumulated in the copper lineset!

    how much oil would you say is "resting" in the lineset!



    .

  13. #13
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    If you dump the oil. You may have minimized the PPM or moisture.

    So when you do this. Do you give any better warranty to the customer for paying for this, then if you simply used filter driers. Do you guarranty that you have stopped/eliminated moisture trouble.

    I believe in giving the customer what they paid for, and I believe in the customer paying for what they get.
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