Straight Talk About "On-Demand Tankless Water Heaters by A.O. Smith

Discussion in 'Tankless Water Heater Forum' started by SewerRatz, Feb 10, 2009.

  1. dimprov

    dimprov New Member

    Messages:
    38
    Location:
    Austin, Texas
    Ladiesman,

    Your original post said 10 feet, which is more like 3 meters.

    Why not just measure it at 1 meter?

    The HVAC guys measure it at greater distances because they're trying to distort reality by saying their unit is, say, 50db, and then asterisk it to say "oh, by the way, it was measured at more than 30 feet away".

    Sounds measurements at more than 1 meter are a red flag.

    David
  2. sjsmithjr

    sjsmithjr Geologist

    Messages:
    295
    Location:
    Knoxville, Tennessee
    To add to what David posted, you should also take your measurements using the Decibel A filter; dbC is typically only used to measure very high SPLs.

    FWIW, they even had a discussion of tankless technology on the Sound&Vision forum, where Ladiesman271 is equally well loved...

    But wait, Laddiesman271's knowledge base doesn't stop at plumbing and home audio, he also does HVAC. Here's what one professional member had to say about him over on hvac-talk.com: "This loud mouth ain't even a tech and hes giving hvac advice. I checked all his posts and his claim to fame is just putting links to HVAC source information. No solid input of any other kind." It's worth signing up just to check out his posts!

    I don't feel so special anymore...
    Last edited: Feb 13, 2009
  3. sjsmithjr

    sjsmithjr Geologist

    Messages:
    295
    Location:
    Knoxville, Tennessee
    If you could demonstrate that you actually know what you're talking about I would.

    The A weighting curve approximates human frequency response at low to moderate SPLs. dbC would be appropriate if the SPLs were over 100dB.
  4. dimprov

    dimprov New Member

    Messages:
    38
    Location:
    Austin, Texas
    I'm sure noise is a "who cares?" topic for most people. Too bad for them. Ignorance isn't always bliss. I care about getting an accurate noise measurement because I care about getting quality sleep. Yes, quality sleep. Ever wake up tired after a full nights sleep? There are many possible reasons, obviously, but one very real possible cause is environmental noise. Now, I know you tough guys will wave this off, but I'm serious. Wikipedia says threshold for noise producing sleep disturbance is 45 dB(A) or lower. You can prove it in a sleep lab. I've seen the video. It's real.

    Anyway, that's why this is more than academic to me, especially in a scenario where tankless might be used for hydronic heating. I have a typical 4 bedroom house, and no matter where I put it, it could bother the sleep of someone in one of those bedrooms. Plain-vanilla tanked would be the quietest, but I'm exploring tankless alternatives for unusual reasons that I won't bore you with. I might be able to build a custom muffling enclosure, using soundproofing materials, if I used a zero-clearance closed combustion tankless. However, it's not as easy as it sounds. If you nail or screw the tankless to a framing member (in the attic say), then noise will conduct through the nails/screws, bypassing the soundproofing. You still get some benefit, but not as much as if it were fully isolated. The intake/exhaust vent pipes can also transmit/transfer noise from the tankless--not to mention the water pipes themselves. Has anyone thought this through and arrived at a solution? If necessary I'll re-invent the wheel, but I prefer not to.

    David
    Last edited: Feb 13, 2009
  5. sjsmithjr

    sjsmithjr Geologist

    Messages:
    295
    Location:
    Knoxville, Tennessee
    You might look into something like "isotrax" for an interior wall. Off the top of my head I haven't got a clue as to how to isolate exhaust noise on an indoor unit.

    Outdoor unit mounted using isolation hardware?

    You might want to start your own thread to keep your topic out of the weeds.
    Last edited: Feb 13, 2009
  6. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    I have heard comments about the noise from panel mounting being transfered to the frame of the house in other threads on forums. Isolation mounting would be highly desireable for this reason.

    I'm convinced that we can't get any subjective statements from either Greg or Laddy Boy on this...
    One offers an estimate based on his ear comparison to a vacuum cleaner I think it was and the other was a guy that the airlines would love to have measuring the sound level of their jets taking off at an airport with noise limitations... "It was pretty quiet on the DbZ scale 10 miles away!":eek:
  7. dimprov

    dimprov New Member

    Messages:
    38
    Location:
    Austin, Texas
    Thanks for the feedback and suggestions. I think I'll price out a CMU or ICF exterior structure. They look fairly easy to build.

    By the way, 60 Minutes did a show sometime in the last year or two on sleep deprivation. A sleep lab used intermittent sound to disrupt the deep sleep of young test subjects. In no time at all the measured health of the test subjects declined dramatically. If I remember correctly, they actually had to halt the experiment early because the health effects were more extreme than anyone had predicted. What was especially interesting is that when interviewed the poor bastards said they thought they were sleeping just fine. The truth wasn't revealed to them until after the experiment.

    So just fyi: even if it's killing you, chances are you don't realize it.

    Sweet dreams. :D

    David
    Last edited: Feb 13, 2009
  8. sjsmithjr

    sjsmithjr Geologist

    Messages:
    295
    Location:
    Knoxville, Tennessee
    Best of luck to you on your project David, whatever the heck it is! :D By the way, based on your location, you might want to look into dry stacking with a bonding coat. Send me an IM if you want to discuss it further.

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