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Thread: DSS-chapter 17

  1. #1
    Join Date
    Dec 2007
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    Soudern Kal-e-phone-e-ya
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    278

    DSS-chapter 17

    Well, its back. The smell. Every Monday morning. This week, worse than its ever been......

    AHU- 25 HP motor on a speed drive.....hot and cold water/air coils. Conventional (blanket) filtration....(yes, in excellent condition and changed quarterly)

    Problem began about 2 years ago. The typical complaints......stinky....sour milk, dirty socks smell. At first I could not smell it. Now, not so much.

    Once we realized we had a problem, I began cleaning the coils. Removed a bunch of lagging which appeared "moldy". (had the industrial hygenist from our risk mgmnt. department take some tape samples, results were that there "was some mold present", however; the lagging did not have an odor. It was determined that this (the lagging) had a mold that occurs everywhere, but was concentrated due to the large volume of air passing over it.
    I was taking a class at the time, and this website was mentioned, so my search for information began.

    First, I rescheduled the AHU to run continuously 24/7, instead of 0400-1159 x 5 days. This did seem to help. However, we began to notice that the odor did not manifest itself unless the chillers were running......AHA!

    So, thru some research called internet surfing, we have learned that its the moisture triggering the "blooms".

    At first, cleaning the coils had little effect, except to "overcome" the odor with the odor of the cleaner. However, a pattern emerged which is consistent to this date. Monday mornings, after the coils have been dry since friday nite, they get wet, and the smell occurs.

    These chilled water coils, CU to CU, are about 13" thick. I could not see water coming out of the other side, even when we used a power washer, wide tip. So, purchased a dedicated coil cleaning machine.....Goodway CC-600. What a great piece of equipment!

    Came in on a sunday, used the "evil yellow foaming" coil cleaner first. Was advised to clean in the opposite direction as the air flow. I went thru 4 gallons of that stuff, and still could not get the solution to come out the (upstream) other side. Then came the bleach. (I know, I know, but I was careful and did not let it sit too long). Rinsed x 4. Completely. Ran the system, and it was fine for about 3 weeks.

    This monday, wow, it was bad.
    So, my next step: Clean them again with the foaming cleaner, from BOTH SIDES. I will then bleach them again, rinsing generously of course.

    Got a quote of $40K to replace the coils, Im here anyway so cleaning the coils is a much cheaper prospect to the company.

    I dont want to have to worry about this stuff forever, so Im gonna give it one (or 2) more tries before I recommend replacement.

    Any thoughts or suggestions?

  2. #2
    Join Date
    Jun 2006
    Posts
    147
    I would contact the Mfg and have them take a look at it. I assume it isn't leaking ( the coil). Does this unit have a humidifier?? I used to have phosphate based water treatment in our boilers and it was over dosed which caused the steam from the humidifiers to stink. Just thinking out loud. Good luck

  3. #3
    Join Date
    Dec 2007
    Location
    Soudern Kal-e-phone-e-ya
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    278
    no, I'm convinced (by monitoring nitrate levels in the loops) that we are not losing water.
    Also, no smell in the hot deck, only the cold deck.

  4. #4
    Join Date
    Feb 2003
    Location
    Wichita Ks
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    1,467
    I wonder if there is some chemical in the air that might might condensing on the chill water coil?

  5. #5
    Join Date
    Jun 2006
    Posts
    147
    Any new plumbing vents in the area of the OSA?

  6. #6
    Join Date
    Mar 2003
    Posts
    7,321
    Is there any chance your drain piping is losing its trap prime over the weekend, and allowing gase to back up? how is it piped? A unit with thirteen inch chilled water coils would be running, I imagine around four inches static or so. Is the trap big enough to drain properly or do you have issues with coil pan drainage? Is it possible that your air velocity is too high acroos the dry coil, causing carryover and wetting the insulation downstream? Will batman get out of the penguin's stranglehold and save the day?

  7. #7
    Join Date
    Feb 2004
    Location
    New Mexico
    Posts
    5,490
    Where does your fresh air come from?
    If from a pit that sometimes fills up with a lot of leaves and stuff.
    I've had pigeon nests in OSA intakes.

    I guess I would consider that the coils aren't creating the smell they might just be a place that accumulates the stuff.
    Tracers work both ways.

  8. #8
    Join Date
    Sep 2008
    Location
    Cedar Rapids, IA
    Posts
    486
    If there is material inside a 13" thick coil you are not going to get it clean with any method you haven't tried already. Replace the coil. Just for chuckles post the weight of the new coil vs the old one. I bet the old one is considerably heavier.

  9. #9
    Join Date
    Oct 2006
    Location
    Hampton roads VA
    Posts
    51
    take your A/C in your car or truck.Run the a/c steady for several days.Let the car sit over the weekend start it up and turn on the a/c when the coil get`s nice and cold and wet some times you will get the same smell you are talking about as long as you keep chilled water flowing through the coils and the have a certian amount of condensate on the coils the smell should go away.I am not saying this is a sure fix but it is a thought.

  10. #10
    Join Date
    Oct 2006
    Location
    Hampton roads VA
    Posts
    51
    Take your A/C in your car or truck.Run the a/c steady for several days.Let the car sit over the weekend start it up and turn on the a/c when the coil get`s nice and cold and wet some times you will get the same smell you are talking about.As long as you keep chilled water flowing through the coils and the have a certian amount of condensate on the coils the smell should go away.I am not saying this is a sure fix but it is a thought.

  11. #11
    Join Date
    Nov 2003
    Location
    Montreal, Qc.
    Posts
    780
    How many fins per inch are the coils?

    How many square feet are they?

  12. #12
    Join Date
    Dec 2007
    Location
    Soudern Kal-e-phone-e-ya
    Posts
    278
    72 sq ft. 9/inch

    I already extended all of the plumbing vents on the roof, as that is where the OSA comes from.

    Drains, 1" CU. Pans tilted correctly, draining fine. Have not found a dry trap to date.

    Chemical condensing? Dont think so, but some of these ladies around here sure like the perfume!

    I am almost certain its in the cold coils. for kicks, when it happened on Monday, I shut down the chilled water, gave it 2 hours, and the smell was gone. (the coils were dry). Opened the valve, and in about 2 minutes, the smell was right back.

    I might have figured it out.

    (bought the new machine, there IS a learning curve)

    Cleaned them again today, this time, I put the nozzle of the 600 PSI washer right up to, even touching the coils. (yes, I will need to break out the comb) Foamed it good, actually saw it foam out the other side. Long process.....but Im crossing my fingers. (and taking monday off!)

    Will keep the thread updated as I find out if it worked.

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