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I've created an Accidental Trombone from my water heater vent piping

artnkingartnking Posts: 4Member
edited December 2016 in THE MAIN WALL
DIY guy here who just installed a new Westinghouse 50-gallon water heater, model WGR050NG076. This is the same as the HTP PH76-50. I used 2" PVC piping for air intake and vent from my basement, and sideways through the concrete wall and venting on an outside wall. I inadvertently created a trombone. The water heater fan is on a resonant frequency that causes a low frequency rumble that can be heard throughout the house, and outside in the yard.
Here is a link to a 1-second video of the outside vent. You can hear the noise in the video.
https://goo.gl/photos/Ma5VWEWywwKHwiks7

Here's a link to two photos, showing the PVC piping inside and outside the house.
https://goo.gl/photos/14TLmnnnY9gWqi9e8

I'm looking for advice on how to get rid of my accidental trombone. Thank you!

Comments

  • Jamie HallJamie Hall Posts: 10,478Member
    The only way to get rid of a resonance is to change either the driver -- which is the fan, which you can't do -- or the length of the pipe. Which you can do. That may or may not work...
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • hot_rodhot_rod Posts: 11,468Member
    You might be able to dial away the sound, not unlike the foghorn post below. Did you check the burner operation with a combustion analyzer?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • AbracadabraAbracadabra Posts: 1,948Member
    Isn't the exhaust too close to the window?
  • j a_2j a_2 Posts: 1,796Member

    Isn't the exhaust too close to the window?

    Not if it's a direct vent, and it appears to be....but worth checking the book....you definitly don't want the intake air sucking in the exhaust...HO sit back and read the manual, come back with any clarifications you may need help with...Beg borrow or steal a combustion analyzer, but do get one and post your readings...can't help much with out those readings
  • GordyGordy Posts: 9,264Member
  • artnkingartnking Posts: 4Member

    The only way to get rid of a resonance is to change either the driver -- which is the fan, which you can't do -- or the length of the pipe. Which you can do. That may or may not work...

    I've got the space to change the pipe length and layout. My total pipe length is well below the maximums called out in the manual. If I re-routed the pipe and made it a foot longer, or broke up the longest run, would that likely help?
  • artnkingartnking Posts: 4Member
    j a said:

    Isn't the exhaust too close to the window?

    Not if it's a direct vent, and it appears to be....but worth checking the book....you definitly don't want the intake air sucking in the exhaust...HO sit back and read the manual, come back with any clarifications you may need help with...Beg borrow or steal a combustion analyzer, but do get one and post your readings...can't help much with out those readings
    The distance from the vent and the intake and the window are well in excess of the minimums called out in the manual. I'm a newbie, so this may be a dumb question, but please explain how readings from a combustion analyzer would help me with my resonant noise problem.
  • Bob Bona_4Bob Bona_4 Posts: 2,083Member
    Excess air can cause light off harmonics. Would be good to get a baseline on your combustion settings.
  • IronmanIronman Posts: 5,042Member
    It's not the piping - if it's the correct size.

    The harmonics is in the combustion which is why a combustion analysis is MANDATORY.

    As Bob mentioned, probably too lean a fuel/ air mixture.

    The CSST connector that you used in the gas line can also be a factor. Either get rid of it or go at least one diameter larger.

    Your problem is a common occurrence with negative pressure gas trains and we deal with it often. Get the combustion mixture to the rich end of the manufacturer's specs and get rid of the connector. One or both should silence your trombone.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • artnkingartnking Posts: 4Member
    Ironman said:

    It's not the piping - if it's the correct size.

    The harmonics is in the combustion which is why a combustion analysis is MANDATORY.

    As Bob mentioned, probably too lean a fuel/ air mixture.

    The CSST connector that you used in the gas line can also be a factor. Either get rid of it or go at least one diameter larger.

    Your problem is a common occurrence with negative pressure gas trains and we deal with it often. Get the combustion mixture to the rich end of the manufacturer's specs and get rid of the connector. One or both should silence your trombone.

    Ironman, you were exactly on target with your advice. I finally got on the schedule with a local heating contractor who came out with his combustion analyzer and gas manometer. With a little help from the Westinghouse tech support people, he was able to adjust the mixture and eliminate the harmonic noise. As a bonus, his combustion analyzer showed that his changes had also increased the efficiency from 87% to 95%.

    Thank you Ironman!
  • IronmanIronman Posts: 5,042Member
    Glad that fixed it.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
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