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Thread: air in piping

  1. #1
    Join Date
    Jan 2009
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    Not in Iran
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    1,076

    air in piping

    At site, system has 1 80 ton RTAA with 12 CWAHU and 2 liebert fcu,
    I have been bleeding off air at the highest point in the system, prob 15 cubic feet of air, the coil temp went from 78 to 52, the next day same issue, So i decided to add auto air vents, well no more problems there but now also on the highest floor, another mechanical room is AIR LOCKING another cwahu,
    so I will BANDAID this as well,

    Question, how does air enter the system,

    1, suction at the pump due to bad gaskets,
    2, incoming auto refill on the cw system due to maybe a possiable leak somewhere, incoming city water having air, which goes to the air seprator first,
    3, air seprator is bad {15 years old} ( what I am thinking) which is at ground level.. there was no air vents at the highest point until i added,

    NOW THE REAL QUESTION,.

    1. There are 2 pumps for the building, estimated 200 GPM per pump,
    ne 80 chiller, one pump for barrel, two pumps for building, redundant.

    2. now, only one building pump is needed ,

    3. the building is getting new BAS and the installer turned on both pumps for the building, and i am thinking that one building pump is pulling water from the other pump (starving each other) .,

    4 QUESTION.,
    IF THERE ARE TWO PUMPS AT 200 GPM EACH, IF BOTH PUMPS ARE RUNNING SHOULDNT THIS EQUAL 400 GPM? I AM THINKING SO,

    5, with one pump running BAS shows estimated 140 GPM supply , with both pumps running BAS show 190 supply GPM.

    WHAT YOU PROS THINK?
    THX brosphers= brothers=fellow service thermodynamic engineers!

    BTW , i was going to have the big dogs come out and give their opinion,.
    no signature blast'em man blast'em
    !!!KILL THE TERRORIST!!!

  2. #2
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,267
    Quote Originally Posted by milkyway View Post
    ...Question, how does air enter the system,

    1, suction at the pump due to bad gaskets, POSSIBLY
    2, incoming auto refill on the cw system due to maybe a possiable leak somewhere, incoming city water having air, which goes to the air seprator first, POSSIBLY
    3, air seprator is bad {15 years old} ( what I am thinking) which is at ground level.. there was no air vents at the highest point until i added, POSSIBLY
    NOW THE REAL QUESTION,.

    1. There are 2 pumps for the building, estimated 200 GPM per pump,
    ne 80 chiller, one pump for barrel, two pumps for building, redundant.

    2. now, only one building pump is needed ,

    3. the building is getting new BAS and the installer turned on both pumps for the building, and i am thinking that one building pump is pulling water from the other pump (starving each other) ., NOT LIKELY

    4 QUESTION.,
    IF THERE ARE TWO PUMPS AT 200 GPM EACH, IF BOTH PUMPS ARE RUNNING SHOULDNT THIS EQUAL 400 GPM? I AM THINKING SO, GENERICALLY SPEAKING, YES, PRACTICALLY SPEAKING, NO...BUT CLOSE. IT DEPENDS ON THE PIPING. IF THE PIPING WAS SIZED TO FEED BOTH PUMPS, THEN GREAT, BUT THE PUMPS MOVE WATER BASED ON DIFFERENTIAL. WITH BOTH PUMPS ON, THE DIFFERENTIAL GOES UP AND THE GPM GOES DOWN PER PUMP...TEST IT AND TRY IT AND PLOT IT ON THE PUMP CURVE

    5, with one pump running BAS shows estimated 140 GPM supply , with both pumps running BAS show 190 supply GPM.

    WHAT YOU PROS THINK?
    THX brosphers= brothers=fellow service thermodynamic engineers!

    BTW , i was going to have the big dogs come out and give their opinion,.
    sounds like a fun building!
    my 1st time jumping out of a plane...http://youtu.be/Kv38G0MHsGo

  3. #3
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,995
    Adjusting make-up water pressure regulating valve so that the lowest pressure anywhere in the system (typically pump suction or highest physical point) is 5-10 psig should help prevent air from entering.

  4. #4
    Join Date
    Mar 2004
    Location
    ottawa canada
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    2,022
    How about restriction in flow to suction side of pump causing pump to cavitate and create air bubbles which make 1 big bubble which gets trapped at the highest point .
    Dirty strainers are a big culprit .
    Undersized piping
    Poor piping design etc etc
    The 64 roars to life Whoo hoo ...shes a rolling chassis .
    You bend em" I"ll mend em" !!!!!!!
    I"m not a service tech.. I"m a thermodynamic transfer analyst & strategic system sustainability specialist
    Best Austin Healey In Show twice in 2013 .....All those hrs paid off .

  5. #5
    Join Date
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    Like those simple fix

    FOUOND IT. LOL



    thanks for the replies.,

    Attached Images Attached Images
    no signature blast'em man blast'em
    !!!KILL THE TERRORIST!!!

  6. #6
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    1,995
    What izzit? A drain on some device? What is the device? I would still prefer to not have anything in a vacuum. It's usually easier to find and fix a water leak than it is to find leak sucking air. And the system will tolerate a water leak out better than it will an air leak in.

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