Dripping Sound from Attic Furnace/AC?

Discussion in 'HVAC Heating & Cooling' started by AlGreen, Jan 1, 2017.

  1. AlGreen

    AlGreen Member

    Joined:
    Jul 25, 2016
    Location:
    New Jersey
    Lately I've been hearing a dripping sound coming from one specific part of the ceiling in the second floor master bedroom. I've gone up to the attic (insulated) and looked for signs of a leak in the area, but can't find anything. There are no pipes that I can see under the plywood flooring.

    The sound is, however, close to where the upstairs zone gas furnace and central air components are mounted, which includes some PVC piping to drain condensation outside.

    I've read that PEX can move against wood and make a dripping sound. If that's true, I'm wondering if something similar could be happening with the PVC. Thoughts?
     
  2. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    PEX against wood may make a ticking sound, but it's only rhythmic if it's changing temperature fairly rapidly.

    Is it a condensing furnace?
     
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  4. AlGreen

    AlGreen Member

    Joined:
    Jul 25, 2016
    Location:
    New Jersey
    It's an older Lennox natural gas furnace connected to one of two Carrier AC units outside.
     
  5. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Older can still be condensing (there are condensing Lennox units going back to the mid 1980s). Got a model number?

    Hard-piped ducts can sometimes tick with expansion & contraction when heating up or cooling off too.
     
  6. AlGreen

    AlGreen Member

    Joined:
    Jul 25, 2016
    Location:
    New Jersey
    I'll have to remove the panel tomorrow to find the model number. Here are a few shots of the setup in the meantime.

    2017-01-04 19.10.11.jpg 2017-01-04 19.09.43.jpg
     
  7. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    The B-vent exhaust venting is not designed for a condensing furnace, and it looks like the 80% efficiency Elite G50. I guess that rules out issues with the exhaust condensate management components (since it has none.) Unless the AC is running you shouldn't have any liquid in the AC condensate management plumbing & pan.
     
  8. AlGreen

    AlGreen Member

    Joined:
    Jul 25, 2016
    Location:
    New Jersey
    So it's a Lennox Elite G24M (X), though it sounds like that isn't a factor now.

    I live in North NJ, and the AC has definitely been off when I've been hearing the noise. When I measured where the sound is approximately centered in the ceiling, the spot correlates with the area at the end of the tape measure.

    2017-01-05 12.50.33.jpg 20170105_122538.jpg


    The plywood isn't wet there, and when I pulled it up and moved the insulation aside, the plaster and lath ceiling looked dry. I'm baffled.
     
  9. MKS

    MKS Member

    Joined:
    Apr 15, 2016
    Location:
    Illinois
    Is there a humidifier that maybe misbehaving?
     
  10. AlGreen

    AlGreen Member

    Joined:
    Jul 25, 2016
    Location:
    New Jersey
    Nope, we don't have a humdifier.
     
  11. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    Might be some duct work or air register expanding or contracting. Even if there is no duct work where you hear it, it acts like a giant drum. Noise can propagate quite easily around the home.
     
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