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  1. #1
    Join Date
    Oct 2010
    Posts
    22

    Flood in Air Handler

    We have been having a spell of rainy humid weather here in the northeast and I came in this morning to find my Haakon AHU with about 4" of water throughout the bottom of the air handler.

    I have 2 drains on the unit. One in the humidifier compartment and one after the cooling coil in the blower fan compartment.

    I found that due to the vacuum created by the blower running it was not allowing my compartments to drain properly. Once I popped the doors and allowed the pressures to stabilize in the compartments, the water began to drain. Water was flowing freely through the drain pipes. They are not clogged.

    My situation is this:

    This AHU supplies an ISO 7 clean room and our SOP states that if for any reason the unit has to be shutdown and discharge air pressures fall below allowable tolerances then we need to perform a cleaning of the room. Fortunately my room was out of service at this time, however we plan to be bringing the room into service and our operations can not afford to have production stop so they can reclean the room if I have to shutdown the AHU to drain it out again.

    Any suggestions?

    Picture Below. The two yellow arrows are pointing to the drains.

    Name:  Haakon.jpg
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  2. #2
    Join Date
    Oct 2010
    Posts
    22
    any ideas? I'm stumped and so is everyone I've called in the industry as well.

    They all tell me to make sure my traps are primed and my lines are clean which they both are.

  3. #3
    Join Date
    Jan 2007
    Location
    Stongsville Oh
    Posts
    931
    Do you have magnehelics across the filters, what are they reading? The only reason people are as you say "stumped" is because you give no info what so ever. What is trap depth? What is the pressure exerted on the trap? Does this unit run 24/7? Is the chilled water valve closed when unit goes to unnoc.? Is the interior of unit sweating during off cycle? Are the filters soaked? Are you getting rain water in with your 100% oa unit? Is it 100% OA unit? Are OA dampers closing? Is humidifier shutting off on limit or airflow? Is humidifier leaking? Is chilled water coil leaking? Call someone qualified, at least he will ask the right questions.
    My car didn't start this morning! Why? Oh by the way it's blue!
    ckartson
    I didn't write the book I just read it!

  4. #4
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,724
    Maybe a closed damper creating a massive negative pressure ?

  5. #5
    Join Date
    Sep 2002
    Location
    Hampton Roads, Virginia
    Posts
    1,629
    Are the drain traps deep enough? they should be at least the numbers of inches max negative pressure plus 1", so if say you can run at -5" wc then the trap needs to be at least 6".
    "There are 10 types of people in the world.. those who understand binary, and those who don't."

  6. #6
    Join Date
    Oct 2010
    Posts
    22
    I'm still waiting on the qualified people to show up since the local Johnson tech isn't available until next wednesday.

    as far as the questions go....ask and ye shall receive....

    The mags across the filters are reading a 0.6" pressure drop. They are relatively new and this is typically where they run.
    The unit runs 24/7 and is never unocc. It is roughly 85% RA.
    There is no rain water coming in and it is not my humidifer or cooling coils leaking. It is condensate.

    The unit has a return air fan and I did discover that my RA static is ridiculously high. I am running around 3"wc and the system designed setpoint is 0.6"wc.

    I have gone through and checked all my RA and SA vav's and found nothing out of whack. There are no broken dampers and all boxes are hitting their programmed design cfm setpoints.

  7. #7
    Join Date
    Oct 2010
    Posts
    22
    oh and my traps are about 8 1/2" deep.

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