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  1. #1
    Join Date
    Oct 2006
    Location
    TUCSON, AZ
    Posts
    49
    Me and my fellow workers are coming across some interesting problems with AAON package HVAC units which are 6 to 10 years in service. Evaporators are becoming clogged externally, even if filters are changed on a regular basis, because they are so thick {coils} they are impossible to clean or clear which results in high static pressure, will not drain properly. Anybody out there can relate?

  2. #2

    ...

    What type of filters are you using?

  3. #3
    Join Date
    Dec 2005
    Posts
    1,823
    That's no brainer there. Clean it up (it is not immposible. It is just costly) well and use better filters.

  4. #4
    Join Date
    Sep 2006
    Location
    Tennessee
    Posts
    399
    How about cleaning them real good, using better filters, and installing some germicidal lights if possible.
    UA LOCAL 614...WE DO IT RIGHT THE FIRST TIME

    Always remember, those who hate you don't win, unless you hate them. And then, you destroy yourself. -Richard Nixon-

  5. #5
    Join Date
    Oct 2006
    Location
    TUCSON, AZ
    Posts
    49
    Originally posted by bdclark
    How about cleaning them real good, using better filters, and installing some germicidal lights if possible.
    We use the best pleated filters on the market and we have tried to power wash using chemicals but due to the fact the coils are 8 inches thick and not sure how they are interlocked, we stil get high static presure....you are right it is no brainer here, it just ain't coming clean unless we attempt high very high pressure using very hot water which we are not set up to do

  6. #6
    Join Date
    Oct 2006
    Location
    TUCSON, AZ
    Posts
    49
    Originally posted by hvacman77
    Originally posted by bdclark
    How about cleaning them real good, using better filters, and installing some germicidal lights if possible.
    We use the best pleated filters on the market and we have tried to power wash using chemicals but due to the fact the coils are 8 inches thick and not sure how they are interlocked, we stil get high static presure....you are right it is no brainer here, it just ain't coming clean unless we attempt high very high pressure using very hot water which we are not set up to do
    we the unwilling, attempt to do the impossible with little or nothing to go by

  7. #7
    Join Date
    Dec 2005
    Posts
    1,823
    HVACman77,

    can you remove the coil out and clean it? It's only 20 tons. Piece of cake.

    Once you have it cleaned. Watch out for the GOOD filter plus high static coil plus bad design --- The water shall be sucked out of the pan if you have too much static.

    Pull it out. It's only money if the owner want to get it done right. Otherwise you'll be putting bandage.

  8. #8
    Join Date
    Oct 2003
    Location
    South Carolina
    Posts
    1,241
    Just out of curiosity, have you checked static with the filters removed?
    I had a similar problem with another unit and found it was the filters causing the problem, even though they were fresh.
    Put in different filters and the problem went away.
    “Two things are infinite: the universe and human stupidity; and I’m not sure about the universe.” —Albert Einstein

  9. #9
    Join Date
    Oct 2006
    Location
    TUCSON, AZ
    Posts
    49
    We are still in cooling season her in Tucson, I think in december we are going to yank one esp at the store which is the worst and replace it...see what happens....my gut feeling the coils are so thick that they are interlocked in design very hard to clean. Also talk arround our company is that we are getting a hot water high presure washer, if we get one Ill try it. I put this question out there to see if any other people were experiencing the same problems

  10. #10
    Join Date
    Dec 2003
    Location
    Northern VA
    Posts
    619
    If you have used a power washer on this coil, how did you do it and what kind of psi is it?
    I understand that sometimes you would want to use a small power washer to kick up the pressure on a high rooftop of an old building where they don't DARE raise the potable pressure above 30 lbs. for fear of blowing out the old supply plumbing.
    But if you are using the power washer to really clean the ****e out of the fins-they may now be bent so bad that a year and a day with a butter knife in hand ain't gonna straighten it out.
    I'd only ever use a high foaming chemical and about 60 psi thru a garden hose nozzle at best.
    "Iron sharpeneth iron..."

  11. #11
    Join Date
    Jan 2004
    Location
    Location: Tulsa Oklahoma
    Posts
    222
    We live in Tulsa a few miles from the Aaon factory. You should call their engineering department and see what suggestions they have. They are down to earth guys and
    willing to help.

  12. #12
    Join Date
    Aug 2004
    Posts
    20

    AAON 20 Ton Evap

    Call AAON and maybe you will be lucky to get a return phone call in 2-3 days, but they will only try once. The service tech.'s have caller ID and never answer calls, just return calls in the order that they came in. The caller ID is to identify internal calls. However, their coils are no different than thick coils used in chilled water systems that may even be 12" deep or more for 8-10 row coils. AAON's max is 6 rows deep.
    Clean filters are the key, but the AAON filter racks are notorious aof allowing air to bypass around them, particularly on the access door side. id you call AAON to talk to a service tech., you will be referred to the parts department if the RTU is not in warranty. Weird way to do things.
    In defense of the ocils, they did not use the enhanced fin (AKA Lance Fin coils) except for about a year. Their coils are continuous sinusoidal ( Thanks for the terminology Trane) so there is no place for the dust and dirt to stick. The condensate sould wash most of the dirt off of the last 2 rows of coil and the entering air side should be cleanable with a foaming/expanding type cleaner.
    On newer units, there is an option for a filter or lint guard on the outside air hood to catch large birds, bugs, etc before the mixed air filters.

  13. #13
    Join Date
    Jan 2004
    Location
    Location: Tulsa Oklahoma
    Posts
    222
    Thanks for the feedback. I am supposed to take an A/C class over their this month on tour and will deliver your
    comments to the Corporate President. I don't know that he is aware that so many people are dropping the ball. Sometimes it's necessary to ring the "Wake UP Bell" real
    loud to get things done the way they should be.
    Whoa Maynard - that's not how it works.

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