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  1. #14
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    As far as it running in a vacuum for Ninety second, I don't know how many times the LP alarm was reset. This system has a Two second pump out, and on 407C it will drop to about 30PSI.

    So if you run it for another Eighty-Eighty seconds, where would the vacuum be?

    Also recently I had a tandem that the solenoid coil burned out, both compressor fried. Same Panasonic compressors, condenser full of oil. Again the unit had a Ninety second time delay on LP cutout.

  2. #15
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    Sounds to me like more of a problem with oil return than running in a vacuum.

  3. #16
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    Well; the manufacturer sure seems to think: more than 90 seconds. <g>

    I have been told with horrified seriousness to never run scrolls in a vacuum! Not Ever! Certain Death!!!

    As with many things which don't make sense to me; I kept probing for the exact genesis of the warning. And as is very often the case: Everybody knew the endless-repeated Caution - Nobody knew the core reason for it. <g>

    Not too too long ago I was talking to a Copeland rep. about some things and the vacuum-prohibition thing came back to me. He just parroted The Warning at first but I probed for the engineering reason. What exact bad thing will happen? Why is it unique to scroll compressors?

    The answer from the design boys was that a scroll is considered to be a positive displacement compressor with very low internal leakage / high efficiency and as such it is theoretically capable of achieving very deep vacuum levels. So the possibility exists that a scroll could create a low enough internal vacuum to allow internal arcing of the motor windings.

    The prohibition isn't really against Any vacuum - it is only against a deep (evacuation grade) vacuum.

    I can't see why a scroll wouldn't run as long as any other hermetic compressor while in a moderate vacuum. If you can; I'd like to hear your logic.

    PHM
    ---------





    Quote Originally Posted by jimp View Post
    Its on a chiller.

    But how long can a scroll last running in a vacuum?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  4. #17
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    Or low and/or erratic SSH.

    Quote Originally Posted by BNME8EZ View Post
    Sounds to me like more of a problem with oil return than running in a vacuum.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  5. #18
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  6. #19
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    One of my favorite parts of this “vacuum concern” is that “everybody” says that you can’t run a compressor in a vacuum. What is the difference between 0.1 psig versus -0.1 psig? In reality, there is no difference to the compressor. But manufacturers take phone calls from techs who have ZERO knowledge about what they are doing, so the manufacturers just give a blanket statement.

    The key is to understand where is the absolute lower allowable pressure the compressor can run. While I don’t know this exact number, there are going to be many factors that are involved.
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

  7. Likes icy78 liked this post.
  8. #20
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    .
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

  9. #21
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    I was taught by Copeland at their COSS class about Scrolls before they hit the "streets" and again years after that class. As said in this thread,Scrolls can not handle a "deep vacuum". They can handle a vac above that deep vac point. Scrolls were never made/produced to operate in a vac. As said, its the beauty of a Scroll to operate so wonderfully that it does create a deep vac rather quickly,killing itself. Simply front seating the SSV can kill a Scroll due to the deep vac being created so fast.

  10. #22
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    Let's say we have a scroll pumping R-404. We want to run a -45 F. box. That will require a suction pressure of about 3-4". Assuming proper SSH and DSH - how would this 'running in a vacuum' cause harm to the low-stage scroll?

    PHM
    --------


    Quote Originally Posted by jayguy View Post
    One of my favorite parts of this “vacuum concern” is that “everybody” says that you can’t run a compressor in a vacuum. What is the difference between 0.1 psig versus -0.1 psig? In reality, there is no difference to the compressor. But manufacturers take phone calls from techs who have ZERO knowledge about what they are doing, so the manufacturers just give a blanket statement.

    The key is to understand where is the absolute lower allowable pressure the compressor can run. While I don’t know this exact number, there are going to be many factors that are involved.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  11. #23
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    Quote Originally Posted by Poodle Head Mikey View Post
    Let's say we have a scroll pumping R-404. We want to run a -45 F. box. That will require a suction pressure of about 3-4". Assuming proper SSH and DSH - how would this 'running in a vacuum' cause harm to the low-stage scroll?

    PHM
    --------
    From my view point life would be a joy. From Copelands view point, I think you would need Factory Approval.

  12. #24
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    Running in a vacuum causes scroll failure or I should say scroll compressor failure, by causing a short at the fuseite connections.
    Is that because there's no cooling effect and the Heat at that point causes breakdown?

    Sent from my SM-G950U using Tapatalk

  13. #25
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    Quote Originally Posted by icy78 View Post
    Running in a vacuum causes scroll failure or I should say scroll compressor failure, by causing a short at the fuseite connections.
    Is that because there's no cooling effect and the Heat at that point causes breakdown?

    Sent from my SM-G950U using Tapatalk
    On Recip comps that are under a deep vac,there is a "warning". And that would be "DO NOT ENERGIZE THIS COMPRESSOR" because of the same type of electrical failure can/will happen. Using a Megger on a comp in a vac is not recommended,either. KindaSorta look at the "atmosphere" inside the comp motor section(freon,some oil vapor) as insulation on a wire. As the vac gets deeper,the "insulation" gets thinner.

  14. #26
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    Quote Originally Posted by TechmanTerry View Post
    ...Using a Megger on a comp in a vac is not recommended,either. KindaSorta look at the "atmosphere" inside the comp motor section(freon,some oil vapor) as insulation on a wire. As the vac gets deeper,the "insulation" gets thinner.
    “Never meg in a vacuum” is also a myth. I have done it. The devil is in the details. In this case, the detail is the POWER behind the megger. Just like static electricity has enough voltage potential to jump a gap and cause a “spark” but you can’t weld with it. A battery operated megger won’t cause a fusite to blow up and be damaged...not enough power behind it...I know this by happenstance. Now a HIPOT would certainly cause damage.

    While i have always understood the vacuum as a “non-insulator” concept, however, I was never able to put it into words. I like your wording very much. Thank you for that!
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

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