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  1. #1
    Join Date
    Apr 2013
    Posts
    6

    Noisy Aaon Rooftop Burners

    I have a 26 ton Aaon rooftop unit that is 3 years old and has since installation made excessive burner noise when the burners initially come on. The burners come on full for the initial 45 second start up and then modulate down. Nothing has been modified on the unit, the gas pressure, orifices, alignment and blowers are all checked out. The unit sounds like a jet engine on the roof. Aaon says its normal.
    Any help would be appreciated.

  2. #2
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,681
    2sac says it's normal as well
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  3. #3
    Join Date
    May 2009
    Location
    South of Heaven
    Posts
    1,151
    And if you ever find a failed inducer motor on these get a new fan wheel with the motor.

  4. #4
    Join Date
    Apr 2013
    Posts
    6
    That would be OK if below the units was a warehouse but its classrooms and they refuse to use the space due to the jet engine noise.
    Has anyone had experience in replacing the burners with quieter ones?

  5. #5
    Join Date
    Apr 2012
    Location
    Louisiana
    Posts
    714
    I doubt replacing the burners is the way to go. Maybe some changes to the duct work? Where is the sound entering the space?

  6. #6
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,449
    Use some flex with a couple 90 degree bends to absorb the sound if possible. Is the gas pressure too high, I've seen some that light with too much pressure and sound like a jet engine.

  7. #7
    Join Date
    Apr 2007
    Location
    Pa
    Posts
    758
    This is normal, is it a drop ceiling? If so install batts of insulation

  8. #8
    Join Date
    Mar 2011
    Location
    Louisiana
    Posts
    119
    This is not an equipment issue as much as it is a building design issue. Architects are using lighter and lighter construction and HVAC designers, in many cases are, not able to place units away from these sensitive areas. This leads to the end result to be exactly what you are complaining about. If it is not burners, then it is compressors or fans, does not matter which brand of equipment is on the roof. To kill sound transmission the structure has to have mass. Unfortunately the perception is that Acoustical treatment costs too much until the owner has a space or building that is uncomfortable or unusable.

    J

  9. #9
    Join Date
    Apr 2013
    Posts
    6
    Quote Originally Posted by jtrammel View Post
    Use some flex with a couple 90 degree bends to absorb the sound if possible. Is the gas pressure too high, I've seen some that light with too much pressure and sound like a jet engine.
    The gas pressure is right at spec.
    thanks

  10. #10
    Join Date
    Apr 2013
    Posts
    6
    Thanks for the reply.
    Yes, it is a drop ceiling, have you tried to spray foam the botton of the roof decking instead of the batt insulation?

  11. #11
    Join Date
    Apr 2013
    Posts
    6
    You maybe right but something needs to be done the space below the unit is unusable. They have a 90 deg duct attenuator to help cancel out the noise but dosen't look like it works too well. Your thinking that the noise is not coming through the ducts but transmitted through the metal roof decking.

  12. #12
    Join Date
    May 2000
    Location
    Salem, WI US
    Posts
    61
    I had some issues with noisey condenser that sat on sleepers that we installed heavy duty vibration springs under the unit to lessen the sound issues. I am not sure if the AAon RTU Curb has options that may include some sort of sound elimination design.
    Betabass



    Success is to be measured not so much by the position that one has reached in life as by the obstacles which he has overcome.

  13. #13
    Join Date
    Mar 2011
    Location
    Louisiana
    Posts
    119
    Quote Originally Posted by ktr52 View Post
    You maybe right but something needs to be done the space below the unit is unusable. They have a 90 deg duct attenuator to help cancel out the noise but dosen't look like it works too well. Your thinking that the noise is not coming through the ducts but transmitted through the metal roof decking.
    That is what I am thinking. The solutions while a pain in the a$$ may get you a usable space. Lift the unit off the curb and put 2 layers of 5/8" gypsum board wall to wall in the curb with a coating of the Green Glue product in between. Be sure to lap the joints and seal the edges. You do not want a pathway for noise. Secondly add a similar solution underneath the roof deck and add some 6" batts on the top of the gyp panels for sound absorption. Make this as large as possible under the unit hopefully 3 - 5' beyond the unit's footprint. I know easier said than done.

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