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Thread: moisture test

  1. #1
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    moisture test



    hi guys,

    if a system is suspect of containing moisture, how can i test it? i beleive its via an oil test from compressor, but will this be acurate as it will come in contact with atmosphere for a short amount of time?

    if i test for acidity is this sufficient? or can i test for moisture? i know moisture makes the oil acidic but im not sure how much moisture is required? hope you understand :/

    we have used a megger on the windings and found no break down of insulation (>1000mOHM)but sight glass is showing slightly wet, if you had dry/medium/wet its on the medium, personaly i dont trust the indiacator as i have had systems before under 2 torr for well over 16 hours and the indiacator still didnt got completly dry???? no rise on rise test either


    thanks guys, have a good weekend!!!!



  2. #2
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    Re: moisture test

    I would start by asking WHY you suspect a system of containing moisture?

    I have asked the same question and have been referred back to the moisture indicator in the sightglass.

    When I have a system that is acting as if it has moisture contamination, my first action is to replace the driers. If I feel that it is a severe contamination, I will do a second change in a day or so.

  3. #3
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    Re: moisture test

    Why trust a stupid litmus paper type thing in a sightglass, after changing driers, evacuation etc.,Try changing the sightglass.
    If a new or gas free system use a vacuum analyser and record rises etc., The vacuum is as good as vac pump can suck, so test ultimate vac reading with analyser before vac-ing system, an oil change in vac pump will add to performance of pump.
    Oil tests with those one shot things from sporlan can be half helpfull. A real test would be an oil analysis by a laboratory with a sample in an air tight bottle, expensive.

  4. #4
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    Re: moisture test

    There are many methods to check gas or oil for moisture content.
    The crackle test - old and not used much any more
    Fluid bottles - which change colour according to moisture content when oil is added
    Gas sample kits - Tests gas for moisture
    Oil analysis at lab - Thorough and accurate
    System indicators - Icing at throtling device (intermittant) or delta T across drier/filter...
    The short exposure to atmosphere usually has no effect on this test which is not cheap and used on bigger systems

  5. #5
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    Re: moisture test

    This is what you do!
    1. Ensure all parts of system are open ie all valves etc.
    2.Ensure that compressor crankcase heater if fitted is on, this helps to unlock any moisture from the oil ensuring good vaccing process.
    3.Connect vacuum pump and vac the gauge manifold only to begin with to prove integrity of lines etc.
    4. If vacuum holds open up lines to system and vac down to at least 2torr.
    5.Stop vac pump and monitor gauges if gauges rise and then stops you still have moisture in system so will need to break the vacuum with nitrogen to 0psi and vac again,you may need to do this three times (what we call triple vac)
    6.Before you re-charge refrigerent make sure you purge your gauge lines otherwise you will put air and moisture back in.

    Good Luck!!

  6. #6
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    Re: moisture test

    Quote Originally Posted by tigger View Post
    This is what you do!
    1. Ensure all parts of system are open ie all valves etc.
    2.Ensure that compressor crankcase heater if fitted is on, this helps to unlock any moisture from the oil ensuring good vaccing process.
    3.Connect vacuum pump and vac the gauge manifold only to begin with to prove integrity of lines etc.
    4. If vacuum holds open up lines to system and vac down to at least 2torr.
    5.Stop vac pump and monitor gauges if gauges rise and then stops you still have moisture in system so will need to break the vacuum with nitrogen to 0psi and vac again,you may need to do this three times (what we call triple vac)
    6.Before you re-charge refrigerent make sure you purge your gauge lines otherwise you will put air and moisture back in.

    Good Luck!!

    Will a standard set of manifold gauges show the small amount of pressure rise associated with moisture boiling off in a vacuum?

    I was under the impression that a proper micron gauge was needed for that purpose.

  7. #7
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    Re: moisture test

    I advice you to invest in one high qulity 4" vacuum gauge.

    I use a Refco one. Only use it when needed.
    Expensive but worth the investment.

    http://www.refco.ch/englisch/index_e.html

    model 19801

  8. #8
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    Re: moisture test

    Of course your right,i should have mentioned that you use a proper torr gauge either digital or compound,there again how would you know that you have achieved 2torr on a standard manifold.Work it out.

  9. #9
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    Re: moisture test

    Quote Originally Posted by tigger View Post
    This is what you do!
    1. Ensure all parts of system are open ie all valves etc.
    2.Ensure that compressor crankcase heater if fitted is on, this helps to unlock any moisture from the oil ensuring good vaccing process.
    3.Connect vacuum pump and vac the gauge manifold only to begin with to prove integrity of lines etc.
    4. If vacuum holds open up lines to system and vac down to at least 2torr.
    5.Stop vac pump and monitor gauges if gauges rise and then stops you still have moisture in system so will need to break the vacuum with nitrogen to 0psi and vac again,you may need to do this three times (what we call triple vac)
    6.Before you re-charge refrigerent make sure you purge your gauge lines otherwise you will put air and moisture back in.

    Good Luck!!

    hi tigger,
    i was taught when doing a triple vac to break with nitrogen and put system to 100psi and leave for ten mins, do i only add to 0 psi and for how long to let it soak up the moisture?

    thanks in advance

    lee

  10. #10
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    Re: moisture test

    Hi

    Regarding vacuum gauges

    At present I am in the M.E. and have used a variety of Absolute vac gauges electronic,but have had some reliability problems with some gauges not lasting very long. and dont have a lot of faith in them.

    I have always reverted back to an old analogue gauge Ive had since the 90s.

    Only real way to check moisture gone especially drying out wet chilers after tube failures.

    Alan

    DOES ANYONE RECOMMEND A CERTAIN ELECTRONIC TYPE HI VAC METER?

  11. #11
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    Re: moisture test

    Check the oil PH and if it is below 7, you should make a preventive cleaning of the circuit and refrigerant, otherwise, you will have acidity in the system in the midterm. the lower the PH is, the soonest you should make that proper cleaning.
    I remind you N2 does not clean the acids away (nor acid away)

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