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Humming A/C

Discussion in 'Electronic Design' started by Mook Johnson, Dec 21, 2004.

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  1. Mook Johnson

    Mook Johnson Guest

    I recently bought a newly built house with a Carrier A/C system. On
    move-inday the A/C was quiet whne turning on with little moretha fan hum.
    I was concerned because the builder placed it outside the wall of my

    after about 6 months of use in texas (hot) it gradually got a 60Hz humm that
    is quite noticable in my bedroom. I checked with my neighbors units and
    there units sound the same so I don't think the A/C is defective (A/C bills
    are inline)

    As there anything I can do to reduce the hum?
  2. Antivibration mountings might be a start, its probably not an
    "electonically solvable problem"


    Serious error.
    All shortcuts have disappeared.
    Screen. Mind. Both are blank.
  3. I guess, the humm comes from the mechanics. The motor is an
    asynchronoeus machine rotating at very close to 60Hz halves,
    or 1800 revs. Any wear or load sounds like a regular hum.
    How about mounting shock absorbers or reducing the mechanical
    coupling to sound ?

  4. Active8

    Active8 Guest

    Custom homes these days often have sound absorbing sheet rock around
    the bathroom to keep the noise from getting out. Maybe that (not
    around the BR, of course) and the shock mounts would help.
  5. Try tightening the transformer mounting bolts.
    This type of problem can range from trivial to maddeningly infuriating.

    Early Tektronix 2513 scopes would howl like a banshee and there was no
    long term fix.

    Many thanks,

    Don Lancaster
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    voice: (928)428-4073 email:

    Please visit my GURU's LAIR web site at
  6. Because of the delay in onset, I suggest you look for places near the
    unit where pipes pass through walls or are clamped to them. They were
    probably isolated with insulation, but this may have deteriorated or
    fallen off, and the vibrating pipes now make contact with the wall.
  7. Mark Jones

    Mark Jones Guest

    Curious, could all the A/C units in the area (inductive loads) be
    creating a slight phase imbalance, which manefests itself as
    extraneous noise?
  8. lemonjuice

    lemonjuice Guest

    Though a motor can be modelled as a transformer due to its inductive
    nature , the sound frequencies are rather different from what seems to
    be the problem. Maybe the presence of harmonics in the load current and
    voltage contribute, as due to the em forces due to leakage currents in
    the motor windings that may cause internal vibrations . I'd still think
    the mechanical component dominates .... but those low frequency em
    origin noises are also there.
  9. Terry Given

    Terry Given Guest

    Dont forget magnetostriction, and of course that dead whit guy, Newton -
    the stator (and rotor) windings are well secured for a good reason.

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