Utica SSC Modcon boiler intake moan noise

Discussion in 'Boiler Forum' started by Matthew Gingras, Nov 1, 2014.

  1. Matthew Gingras

    Matthew Gingras New Member

    Joined:
    Nov 1, 2014
    All, need a bit of help here. I have a utica ssc modcon boiler which is EXTREMELY nice, i love it. However, it makes this "wooo," groan, moan, fog horn, etc noise from the intake venturi. But, if i slightly disrupt the incoming air, the sound disappears. the boiler is properly tuned, and maintained as per manufacturer, and the rest of the system is working well without any problems. please see video, and listen on good speakers, like headphones, or subwoofer computer speakers...not cell phone or tablet speakers, you cannot hear the low tone that im talking about on those:

    Modcon Utica SSC 150kbtu moan groan fog horn noise:


    all suggestions are welcomed, thanks in advance!
     
  2. Matthew Gingras

    Matthew Gingras New Member

    Joined:
    Nov 1, 2014
    Bump...
    Maybe this wasn't clear in my first post, but this sound can also be heard from outside at the exhaust pipe also, I've been trying to get a good sound recording of this at night as this resonance propagates through, and with someone doing the same thing inside to make the sound come and go like in the above video to prove this out. Also, my neighbor has asked me to look into this, since he can hear it; he's been very nice about it and knows it's really not my fault, but I hate to be "that" annoying neighbor.

    Furthermore, it seems it only happens between 50 and 70% firing.

    again, thank you.
     
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  4. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Does it make the noise when the cabinet is closed up tight, and is there a combustion air duct hooked up taking in outdoor air? On p.9 of the manual it appears the cabinet is part of the air intake path, without internal ducting to the blower(?).

    Drawing air across the lip of an un-ducted intake is the equivalent of drawing a violin bow across a taut string. It's finding a resonance frequency in the audible range and driving it with the acoustic pressure out of phase, causing it to ring like a bell or a marimba resonator. The cabinet may be part of the resonator, as well as the intake duct. Does it change frequency when it's all closed up?

    Like all mod-cons, that unit is designed to take ducted outdoor air into that combustion air input. Changing the length of the resonant chamber will change the frequency of the resonance, likely to sub-audible (low frequency/bass) levels. If it's currently without an intake duct, the annoyance may go away simply by ducting it.

    It's also possible that the resonant cavity is related to the exhaust venting length, but that's somewhat less likely. The fact that it only occurs at particular firing levels (= particular blower speeds) means it could be either the exhaust length, the intake length or both.
     
  5. Matthew Gingras

    Matthew Gingras New Member

    Joined:
    Nov 1, 2014
    thanks for taking your time to help me.

    yeah, I've got the intake air piped from the outside with 3" pvc as per the manual. and yes, even with the jacket on the boiler this noise is heard; not as much inside (because the jacket is on in normal operation, and the same config when neighbor chatted with me) but outside at the exhaust pipe, which at night can sound like a distant aircraft continuously flying by.

    When i get home today ill see if changing the length of the exhaust by adding a small section of pipe outside does anything.

    Not that i really want to, but im seriouly tempted to notch that intake venturi slightly, or 3d printing a "castle" head, to make the airflow slightly turbulant or vectored in a spiral to prevent the noise.
     
  6. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    A stub of vent FSK-taped to the blower input might be enough to de-tune it. You could play around with the shape of the edge of the vent to create turbulence without creating permanent modifications to the cast/machined part.
     
  7. Pipemagic

    Pipemagic New Member

    Joined:
    Apr 22, 2019
    Location:
    New Jersey
    I see this s a older thread but did you ever resolve the noise issue with your SSC boiler. I’ve had the same issue it’s usually during warm weather that it makes the moaning noise especially when calling for domestic water. No codes showing on the interface.
     
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