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  1. #1
    Join Date
    Jan 2019
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    Lennox Intermittent Horn Sound

    I have a Lennox EL296UH090XV36C - 2 stage furnace. It makes an intermittent sound like a horn which seems to only happen for 2-5 seconds right after the burner fires up (it doesn't happen every time). The inducer fan sounds normal to me and the horn sound happens before the blower fan increases its speed (which leads me to believe its not the blower fan). The blower is left on at all times. I have posted a video at the following link:

    As I am a new member I cannot post links. I hope its alright that I circumvent this rule by posting the following YouTube id: gDUeWXTn1tA

    If you search this in YouTube my video will come up.

    I read on a different post that it could be the flex line so I tried moving it a bit (as seen in the video) and this seemed to have no effect. It sounded like the horn noise was coming from inside the furnace. A couple weeks ago I had a furnace guy out to do the annual maintenance and he said everything looked and sounded normal. The furnace of course did not make this sound when he was present.

    Happy to provide further info if needed.

    Thanks!

  2. #2
    Join Date
    Jan 2019
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    13
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    Thread Starter
    In a different thread I am seeing the following:

    "With some further research I have been told that this noise may be resolved with adjustment of the air shutter. Noise being related to amount of air pressure which can be variable. "
    and
    "This condition is most prominent with LP gas furnaces but happens with Nat gas too. Air adjustment, gas pressure or orfices not lined up with the burners."

    I am not confident his noise is the same as mine but his description sounds similar. Does this seem relevant? I would like to be able to steer a technician in the right direction.

  3. #3
    Join Date
    Jun 2012
    Location
    Northern NV
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    2,082
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    Look for exhaust gas recirculation...

  4. #4
    Join Date
    Jan 2019
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    Thread Starter
    Thanks Juan Madera for the response. Are you saying I should suggest the technician look into this? Is exhaust gas recirculation not supposed to happen? What would the fix be for the issue? Were you able to view the video I posted on YouTube?

  5. #5
    Join Date
    Jan 2019
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    Thread Starter
    Does anyone have any further input?

  6. #6
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    7,306
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    The density of the fumes and air through the draft inducer changes when the burner lights. I recommend you get a technician with a thorough understanding of the combustion and venting process.
    This site lists those with training according to zip code.
    https://www.myhomecomfort.org/

    Additionally there is a link in my sig to a map site members.
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator: http://www.loadcalc.net/


    There = not here. Their = possessive pronoun. They're = they are
    It's = contraction of it is. Its = the possessive form of it
    Too = also. To = expressing motion. Two = 2
    Then = after that, next. Than = indicates a comparison.
    Questions should end with a question mark "?" Statements end with a period "."

  7. #7
    Join Date
    Jan 2019
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    Thread Starter
    Thanks kdean1. Looks like there is no one anywhere near my Canadian postal code in that link. Any tips on finding a suitable technician?

    Would the issue lie with the inducer itself? The piping? Some connection? I won't be attempting anything myself just like to know what's going on.

  8. #8
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
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    There are many factors involved in the operation of the furnace. Everything you listed is a possible contributor to the sound.

    You should ask any technician you may engage if they can and do measure draft, gas line pressure, and gas manifold pressure. It would be better if they can measure combustion performance as well. Otherwise they are nothing more than a mechanic who can replace parts that are obviously broken.
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator: http://www.loadcalc.net/


    There = not here. Their = possessive pronoun. They're = they are
    It's = contraction of it is. Its = the possessive form of it
    Too = also. To = expressing motion. Two = 2
    Then = after that, next. Than = indicates a comparison.
    Questions should end with a question mark "?" Statements end with a period "."

  9. #9
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    2,217
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    It does not sound normal. How long ago was it installed? When did the sound start? Have you called the installer back to check?
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

  10. #10
    Join Date
    Jan 2019
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    13
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    Thread Starter
    kdean1 - I will make sure to ask about all that over the phone.

    comfortdoc - It was installed by the previous owner of the house in 2015 and has no transferable warranty. I did call the installer but did not get a good feeling from him (and he has awful reviews online). I would much prefer to use a different company if possible. The sound is intermittent. Days can go by without hearing it. It may be anecdotal but it appears to happen in colder weather (i.e., around 0 degrees F or colder). Most of the time that sound is not present.

  11. #11
    Join Date
    Oct 2009
    Location
    God's country - Shenandoah Valley, VA
    Posts
    1,038
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    It's the CSST gas line that causes the harmonics. Enlarge or have it removed and replaced with black iron pipe.

    Proper fuel/air adjustments should be done and MAY resolve the issue. If not, fix the gas line.

    I've got over 150 hours of field experience with this issue in working with manufacturers.
    Bob Boan


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

  12. #12
    Join Date
    Jan 2019
    Posts
    13
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    Thread Starter
    So here is an update on my issue that remains unsolved:

    I had the gas company out to check things over for free. I am not sure what all was checked as my wife was home but he said the gas pressure was a bit too high and reduced it. The issue remained. We had the gas company out again and my wife showed him bobboan's post but unfortunately he just replaced the hose with the same size (but longer) hose. The issue remained.

    I have been able to get a couple more videos with the furnace cover open this time.

    Youtube id ahR19NQYmFs has the horn noise in it (I find it much more audible if viewed on a smart phone rather than computer for some reason). Gas valve clicks at about 0:20 and soon after you can hear the loud sound. I pushed on the draft inducer in this video and there was no change in the sound. It seems like it is coming from the burner area.

    Youtube id kYvHarxmePk shows the furnace operating normally.

    I have contacted quite a few HVAC companies and everyone (including the gas company) says there is no way that it is the flexible gas pipe. With that said, they will change it out (price quoted was $80 for a hard line).

    Someone thought maybe it was a gas valve that was slow to open? He said he could check it with his machine but the sound would need to happen when he was checking it.

    Does this new video help identify the exact issue? It feels like its a gas pressure issue but I could be wrong. Would this sound imply too high or too low pressure? The furnace continues to heat the house well but I stil have this intermittent issue.

    I am happy to pay an HVAC company to come out but they of course are unable to guarantee anything especially if they cannot hear the issue which is why I have been trying to get a better video with the cover off.

  13. #13
    Join Date
    Mar 2013
    Location
    Billington Heights, NY
    Posts
    21,625
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    Quote Originally Posted by wpg-lennox View Post
    I have contacted quite a few HVAC companies and everyone (including the gas company) says there is no way that it is the flexible gas pipe.
    It can be. I had a gas fireplace for deck use that had the same problem. Increasing the size of the gas line and boring out the orifice to a cone shape resolved the problem. It was an issue where the gas supply had to rush down the pipe in order to make the flame look good. (Large pressure drop). The result was a resonating flex pipe.

    Also, tighten the clamps on the inducer hub and the bolts to the inducer mount. It'll help mitigate those rust stains you have.

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