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  1. #1
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    Question about air in system

    When there is air in the system from an improper evacuation, what causes the high side needle to flutter, or maybe more accurately, vibrate into almost invisibility?

  2. #2
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    Come on folks. 56 views and no one cares to explain why the needle flutters when there is air in the system.

    I can't visualize the stuff going on to cause the needle to fluctuate so wildly when there is air in the system. I am thinking it has to do with the air being trapped in one of the condenser coils, and blocking the flow, but that should cause a drop in pressure, not an increase, unless it is only partially stopping the flow and then when pressure hits a high enough level, letting it slip by.

    And I know it has no real bearing on anything, because it requires the system to be charged correctly with no air being present, but the reason it does flutter is interesting from a theoretical perspective.
    Last edited by stonewallred; 05-12-2009 at 09:00 AM. Reason: spelling error

  3. #3
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    its not air in the system, its probably a valve not seating.

  4. #4
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    Quote Originally Posted by stonewallred View Post
    Come on folks. 56 views and no one cares to explain why the needle flutters when there is air in the system.

    I can't visualize the stuff going on to cause the needle to fluctuate so wildly when there is air in the system. I am thinking it has to do with the air being trapped in one of the condenser coils, and blocking the flow, but that should cause a drop in pressure, not an increase, unless it is only partially stopping the flow and then when pressure hits a high enough level, letting it slip by.

    And I know it has no real bearing on anything, because it requires the system to be charged correctly with no air being present, but the reason it does flutter is interesting from a theoretical perspective.
    I'm not typing this to be combative or confrontational but you really have no clue as to what you're looking at and really should work under someone with experience first

  5. #5
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    Actually it is air or was air in the system. After i talked to the person who installed it, he moved the unit after pulling a vacuum, cracked the suction line, cut off the service valves when it started leaking, without cutting it off, and started with the high side first. So, when he got it (the high side) fully seated, he said he had trouble seating the suction side. I assume he managed to pull the low side into a vacuum and sucked air into the unit. When I hooked up the system and got the flutter, I reclaimed the refrigerant, redid his "fix" to the lineset, pulled a vacuum to 289 micron according to my digital vacuum gauge and recharged the system to spec.
    Just because i don't have 5 million posts, or feel I must post on every thread, does not equate to lack of experience. Been paying my bills doing HVAC/R for almost 20 years now cowboy.
    Both as an employee and as a business owner.

  6. #6
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    My best theory would be as follows: Air is a non-condensable, meaning it will not condense to a liquid in the condenser. As the refrigerant passes through the condenser, it picks up small amounts of the air and circulates it throughout the system. As the air/refrigerant mixture passes the point of the access fitting, you read the compressed air pressure and the liquid refrigerant pressure separately, causing it to flutter between the two. Does this make sense? As I stated, this is my best theory. I have no proof of this.
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
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  7. #7
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    Sounds reasonable, I could see that happening in my mind. Sort of like bubbles in a sight glass, air, in the form of gas, and refrigerant in a liquid form and reading it at the service valve at the same time. I have never gotten a clear answer from anyone. Thanks, it makes as much sense as anything I can come up with.

  8. #8
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    Many will not answer technical questions in the resientila forum.
    Since technical questions are suppose to be asked in the pro tech forum.

    Apply for pro membership, if you want answers.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  9. #9
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    Sorry Mods, was I out of line with my answer?
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
    Gene Castagnetti-Director of the National Memorial Cemetery of the Pacific in Hawaii

  10. #10
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    *

    Quote Originally Posted by stonewallred View Post
    Just because i don't have 5 million posts, or feel I must post on every thread, does not equate to lack of experience

    are you feeling a little guilty there Mugsy

    apply for pro membership, maybe you can teach us something



    .

  11. #11
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    Quote Originally Posted by doc havoc View Post
    Sorry Mods, was I out of line with my answer?
    Not yet. LOL
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  12. #12
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    Quote Originally Posted by beenthere View Post
    Many will not answer technical questions in the resientila forum.
    Since technical questions are suppose to be asked in the pro tech forum.

    Apply for pro membership, if you want answers.
    I can see that. Forum has changed a lot since I have signed up. Might see about that pro membership since it is free, lol.
    On the other hand, it was not a technical, DYI question or even related to a specific model or type of unit. Same question would apply to a sandwich table just as easy to a walk-in or a heat pump.
    More of a general interest rather than specific technical question.
    Anywhoo, got stuff to do and little time to get it all done, it's the start of the cooling season around here.

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