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  1. #1

    Done with hvac...going to window units!!!

    I purchased a nice mobile home last year. I have had nothing but trouble with my hvac. After the ac and heat kick off, the ducts in my master bedroom boom and pop and the air handler pops really loud. It does this until it kicks on again. It has never stopped after a year and seems to be getting worse. I've had several people come out and NOTHING can be done. They all tell me that they don't work on mobile homes because the positions of the ducts under the belly. It only does it in my master bedroom which is adjacent to the air unit. I have no warranty anymore and no options. I can't even pay someone to replace all the ducts. It's only a 60 foot trailer. Before I do this, does anyone have ANY suggestions? They tell me it's simple expansion and contraction, but I do not believe this. If that were the case, it wouldn't be isolated and it wouldn't last hours. It would do it in all areas of the house and it would be over in a few minutes. I've even lowered the fan speed. That didn't help. Any suggestions before I go the window unit route? Thanks!

  2. #2
    Join Date
    Aug 2012
    Posts
    2,325
    High static pressure in your ducts while unit is running, window units work though.
    Trying not to be a Hack.

  3. #3
    Join Date
    Aug 2010
    Location
    West Monroe, LA
    Posts
    1,437
    What has the installing company or other companies attempted to do to correct this? Have the researched or lowered the fan speed on the unit?

    This is not normal. My company services a lot of moblie homes and most all systems for them are designed with motors to help overcome high static presure but doesn't always work. The transition from the air handler or furnace to the trunk line may be the probelm?

    Also it not uncommon to see newer moblie homes that have oversized systems and undersized ductwork. This can lead to the system trying to move X cfm but can't so you get what you have which is something has got to give and under high staic presures it often the ductwork that suffers along with the electric usage.

    What kind of ductwork do you have metal or flex? Metal it sounds like? I find it hard to belive that they can't figure it out nt doubting you. Just saying!!! On most moblie homes there is a btu rating sticker somewhere in the home that states what the duct system and home is rated for in btu an cfm.

    If you can find that and compair to current system it might give you and the companies a better idea of the probelm? Also what does the person you bought the home from say about this?

    I just hate for anyone that has central a/c having to resort to using window units as you paid for central heat and air when you bought it.

  4. #4
    The factory said that it was "normal." The dealer told me that my only option was to put a brick in the duct. Then he remarked, "That's trailers for you!" I hired an hvac tech to come out and lower the speed from hi to med/hi. This didn't help at all. The ducts are metal with the thickness of paper. I'm interested in what you said about the actual connection from the unit to the ducts. I always hear a loud clank/pop noise coming from the air handler when the ducts are making their noises. Thank you for your help. You've been more helpful so far than anyone else! I'll keep you apprised!

  5. #5
    The home duct system is rated for 37,600 btu and .3 static pressure if that helps. Again, thank you.

  6. #6
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    2,701
    is that heating btu or cooling btu? usually, there is a CFM limit...
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
    Mel Gibson
    Dwane Johnson
    The A/C repairman

  7. #7
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    Were I to show up at your door to look at this problem, I would want to track down the source of the sound. You can't fix it if you're just guessing where the pop-pop-pop is coming from.

    Since the popping lasts for a long time after the air handler shuts off, whether it has been heating or cooling, I would hedge my bet to begin the hunt at and near the air handler. This is the area where the greatest temperature difference occurs while the unit is running, and any ducts that expand or contract during unit run time will take longer to return to an equalized state than ducts further away from the air handler. That you hear the popping in your bedroom is likely the metal ducts transmitting the sound that far away.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  8. #8
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    My office is a triple wide. The ductwork and air distribution is total junk. I hope yours is insulated better than ours as well. It's probably about 2700sqft and needs almost 200k BTU's just to hold even 68F at 10F outdoor temps. My whole 3200sqft home can hold 70F at 0F outdoors with just 60k BTU's.

    The popping usually means the sheet meatal wasn't installed and formed correctly. You might be able to fix some if it with soem additonal sheet metal screws, maybe some mastic or silicone sealant in the right places. THe noise if hte meatal expanding and contracting.

    Yes, it can be isolated, to only places where the stresses and dimensional changes are most prevalent. Why would it have to occur everywhere? On a hot day, or a cold day with little wind but clear and sunny, go find a long concrete or steel bridge that has a pedestrian walkway. You'll hear the slip joints for the steel guardrails clicking and creaking as the metal expands. The metal will expand only where it has the least resistance to movement... or the point furthest from where it's firmly mounted or secured or where it's most flexible (weakest).

  9. #9
    My house is only 858 square feet. I'm not sure if the btu is cooling or heating. I would have to look it up. I do know that the only place I ever hear the sound is in my bedroom which is adjacent to the air handler. When the unit kicks off, it sounds like people taking hammers and hitting the floor from underneath. The sound travels the length of my bedroom (11 feet) and then I hear a loud POP in the air handler itself. Someone had mention something about a "boot" that connects the air handler to the trunk. Could it have something to do with the unit or installation of the unit and not directly related to the ducts?

  10. #10
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    5,657
    What is the model # of the outdoor unit? It could be as simple as stress on the transition from the air handler to the duct system, or an oversized system on undersized duct. In metal ducts you can usually screw something to the side of the duct to stop duct bang, with mobile home ductwork the ducts aren't accessible and are paper thin, sheet metal screws will shred it like aluminum foil.

  11. #11
    I'm not sure about the outdoor unit. I'm at work right now, but I will get it. How would a tech address the problem if it really is the transition from air handler to trunk system?

  12. #12
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    2,701
    what is the model number of the air handler, and the condenser (outside unit)
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
    Mel Gibson
    Dwane Johnson
    The A/C repairman

  13. #13
    I don't know vstech, but I will get it either at lunch or this evening. I really appreciate your help.

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