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Thread: AC Vibration

  1. #1
    Join Date
    Jul 2006
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    I live on the top floor of a 5-story condo unit. My AC unit (3.5 ton unit) is located on the roof, directly above my kitchen and dining room area. I get a very noticebale vibration coming from the ceiling area when the AC compressor is on.

    I went onto the roof, just to check out how things are set up. The AC unit is resting on two 4x4 pieces of wood. Between the unit and the wood are 4 three-inch by three-inch pieces of rubber ("iso pads").

    Is there anything I do to lower the amount of vibration.

    My initial thoughts were to have the ac unit placed on cement blocks and on bigger isolation pads.

    Can you reccomend a good isolation pad source?

    Thanks for any help.

  2. #2
    Join Date
    Jan 2006
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    Not much really does the trick as far as vibrations go in my experience. You can get vibration dampers and different mounts for the compressor, mabey a jacket for the compressor to make it quieter. The noise is probably not going away though unless you get a nicer condensing unit.

    Best bet is to get someone who sells that brand to check it out. They may be able to sort out the cause of the vibration.

    I have had some success putting closed cell foam sheets under units to spread the weight out over a larger area (more area to absorb the vibration instead of a few little spots like a drum stick on a drum or like putting you hand around a bell). Something to do after making sure the unit is funtioning as best it can.

  3. #3
    Join Date
    Apr 2004
    where you at?
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    kinetics makes a good isolation pad.
    you will likely need at least a 1/4" deflection, possibly more - a distributor will tell you the exact type (possibly a neoprene-steel-neoprene arrangement)

    This will 'help' with the structural transmission, but if it is airborne (low-frequency), the only other measure that would help (in a retro-fit condition) is to add mass directly below the unit and extending beyond its perimeter by 2-3 ft.
    This may be in the form of a concrete pad (not really practical) or multi-layers of gypsum board with a weather protection layer. Something massive in the 3-4 in thickness range.

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