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  1. #1
    Join Date
    Aug 2010
    Location
    honolulu, hawaii
    Posts
    124

    whoomping sound from chw ahu....please help

    I have a 39LA carrier chw ahu, 1992 yr manufactured., belt driven. Making whoomping sound from supply duct side of unit, its a deep bass sound, traveling either from unit
    I already replaced the entire fan assembley, pulleys, sheeves, blower motor. Belt access door is sucking unusually hard, meaning its super hard to open door. While return side., where the filters are is not too bad as compared to the supply.
    Somethings wrong, were thinking the coil is still dirty and needs to be washed again, and fan is causing entire cabinet to pulse creating whoompimg sound.
    Please advise with any suggestions.

  2. #2
    Join Date
    Apr 2010
    Location
    Minnesota
    Posts
    517
    Fan cavitating from high return air static?

  3. #3
    Join Date
    Aug 2010
    Location
    honolulu, hawaii
    Posts
    124
    Yeah could be, any ideas to test to be sure of this? I'm trying to find experiments to test this type of problem to make sure I make the right call, coil plugged restricted ret. Duct etc? Got any ideas? Anything will be useful ? Anyone?

  4. #4
    Join Date
    Jul 2006
    Posts
    32
    Did the noise stop when you opened the door to the fan belt section?

  5. #5
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    Check fan amps and static pressures. All 3 responses so far make sense to me.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  6. #6
    Join Date
    Aug 2010
    Location
    honolulu, hawaii
    Posts
    124

    Wink

    Thx all for your help,
    Amps is well below, I was try to slow down fan to calm sound but it wasn't really working, rla... 9.7. Run amps... 4.7-5.0
    Just from the sound of things without taking static I know that I have a..... high inlet static at fan inlet.... Return statiic at filters is quite low, nothing near inlet at fan, and discharge static well, I'm not too sure but its way less than inlet at fan.
    Aren't inlet and discharge static supposed to be quite equal?
    I'm gonna try take static. I shoulnt have a big difference betwen return static and inlet right?
    Any other suggestions?

  7. #7
    Join Date
    Aug 2010
    Location
    honolulu, hawaii
    Posts
    124
    No noise didnt stop when opening door

  8. #8
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    Low amps is low airflow.
    The evaporator coil is between the fan chamber and the filters. I would guess a high static pressure drop across the coil. Usual cause is dirt. Low airflow.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  9. #9
    Join Date
    Jul 2006
    Posts
    32
    Any fire dampers closed that aren't supposed to be?

  10. #10
    Join Date
    Feb 2010
    Location
    Cal
    Posts
    1,596
    New problem/existing guy or new guy/existing problem?

  11. #11
    I had a similar noise coming out of a 50 ton air handler. Coil was clean, fan section OK and amp draw was low. I found that approximately 1/2 radiation/fire damper grills had closed on the duct system for this unit. It was in a Church with 18 foot ceilings and had another unit supplying air to the same space so the area was cool. I actually had to examine each diffuser to find the problem. After replacing the dampers all is well. The noise was the main duct actually pulsating. It must of been a run of bad links in the dampers that failed.

  12. #12
    Join Date
    Aug 2010
    Location
    honolulu, hawaii
    Posts
    124
    I'm gonna chexk for any fire.dampers, i already opened up.all air dampers trying to see if that would alleviate sound
    Could it be that the chw coils are plugged plugged???

  13. #13
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    Quote Originally Posted by lynn comstock View Post
    Low amps is low airflow.
    The evaporator Make that the chilled water coil. coil is between the fan chamber and the filters. I would guess a high static pressure drop across the coil. Usual cause is dirt. Low airflow.
    Static pressure drop measurements will tell you where the problem is.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

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