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  1. #1
    Join Date
    May 2010
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    R134a molecule size



    Afternoon all

    R134a molecule size, Iv been told that the molecular size of R134a is smaller than OFN
    is this correct?
    Recently leak/pressure checked a freezer on R134 (205grams)
    System was under pressure test for a week with trace gas(5%hydrogen,95% N2)
    With no loss of pressure and no leak picked up with a carbon sniffer.
    On re-gassing with R134a and rechecking with a refrigerate sniffer it again picked up small traces of refrigerate on the evap coil put system into hot gas defrost and the sniffer screams itís head off.



  2. #2
    Join Date
    Sep 2009
    Location
    Iran
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    Re: R134a molecule size

    Hi
    H2 have a smallest molecule in our known world
    your leak may be comes from expansion of evaporator when you cold it and it has tension on pipe or welding tension

  3. #3
    Join Date
    Sep 2007
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    Somerset
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    Re: R134a molecule size

    You are correct there are a number of refrigerants which have smaller molecules that OFN.
    The guys in the know would never leak check without using Trace gas.
    It saves so much time!
    Did you realise that you need a specific type of electronic leak detector though?
    A normal ***** detector will not pick up Trace gas. (Just a thought!)

    I recently left a large chiller on test for days at around 6 bar I could find Nothing.
    Despite knowing there was a leak.
    Dropped the standing pressure down to 1,5 bar (if I remember correctly?)
    Hey Presto!
    Tiny, tiny bubbles around the gland nut of the solenoid valve stem on
    the economiser Side load solenoid.
    When pressurised you could not get near the leak (Just a screaming detector in the general area), but likewise
    Snoop and other good leak detection liquid proved useless.

    Because the leak although minuscule under higher pressures acted like a Air knife.

    Small leaks on 134a system have and always will be a nightmare.
    However trace gas is a huge help.

    Your identifying the leak on defrost says it all!

    205 grams is tiny and would be a nightmare to find.

    The system I was describing has 105 kgs a system and that was a bitch!

    Look for the oil residue that's usually a good place to start.

    Good luck for the future.
    Grizzly
    Despite the High Cost of Living it still remains Popular!

  4. #4
    Join Date
    May 2010
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    uk
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    Re: R134a molecule size

    Thank you for the comments, can confirm the use of carbon sniffer but unusually it didn't pick up any leaks.
    Returned to site earlier this week and removed evap coil for isolation pressure test again using trace gas and submerged in a tank of water.
    Initially no signs of leaks/bubbles until the introduction of hot water into tank to increase water temp then tiny little intermittent bubbles.
    New coil on order

    Many thanks

  5. #5
    Join Date
    Sep 2009
    Location
    Iran
    Age
    60
    Posts
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    Re: R134a molecule size

    Hi

    different between hot water and cold water is expansion of pipes
    it would be happen one in one million test
    good lock

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