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Lochinvar whn 85 fog horning

wjplumbing
wjplumbing Member Posts: 7
in THE MAIN WALL
I am looking for some help in solving a "fog horning" problem with a lochinvar whn85. This boiler will fog horn from 10 seconds to about a minute when it modulates down to 20%. I have tried to tune out the noise with venturi and gas valve adjustments using a combustion analyzer with no results. The boiler rep came down and also tried to tune out the noise with no results. The install is done according to the manufactures instructions and the vent and air intake are within limits. The only way to make it stop is to remove the air intake at the rubber coupling. I don't want to use room air as it is a direct vent setup. Any help or info would be greatly appreciated. Thanks, Jim.

Comments

  • icesailor
    icesailor Member Posts: 7,265
    edited November 2014
    How long is the intake/exhaust from the appliance to the termination. If it is "fog horning", and it goes away when you remove the outside air intake, it is either too much or not enough intake air. If the venting is 3", try putting a 3"X2" PVC bushing in the end and see if it stops it. That would be if there is too much air.

    Does the intake and exhaust travel together for the same length and the same fittings?

    If you disconnected the air intake at the boiler and the fog horn stopped sounding, try cutting the intake inside and away from the boiler and temporally connecting a piece of 3" to the intake. If the horn stops blowing, you might need a bigger intake. Or even cut the intake some point half way from the boiler and see of the horn stops.

    Any possibility its backfiring? Munchkins did something like that. Even though some said it didn't happen.
  • Ironman
    Ironman Member Posts: 7,552
    This is a common issue with that boiler that I've had to correct on about everyone that I've installed. Some were worse than others.
    Simple solution: back out the throttle screw until you reach the richest end of the allowable Co2 range. It's always worked for me, but don't be surprised at how many turns it may take.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • wjplumbing
    wjplumbing Member Posts: 7
    2" Air and vent are close in length but the intake is a little longer. I cut 10 equivalent length off the intake with no change. Both air and vent are close to max length. When richening up the mix to max co2 where's is the co level at? Is it over the 150 ppm limit? Jim
  • Zman
    Zman Member Posts: 7,611
    My experience has been that you can get close to the O2 min/CO2 max and still be reasonably good on the CO (around 90 ppm)
    Are you located at altitude?
    On the triangle boilers they drill a 1/4" hole in to intake elbow to help resolve this phenomenon.
    It does not sound it applies in your case but those boilers will make a similar sound if the gas regulator is too close to the boiler.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • wjplumbing
    wjplumbing Member Posts: 7
    Natural gas meter is close to boiler. Not at altitude
  • Ironman
    Ironman Member Posts: 7,552
    wjplumbing said:

    2" Air and vent are close in length but the intake is a little longer. I cut 10 equivalent length off the intake with no change. Both air and vent are close to max length. When richening up the mix to max co2 where's is the co level at? Is it over the 150 ppm limit? Jim

    Check for the max allowable numbers in the manual. I don't think I've ever seen the CO go above 60ppm, but my mind is a little numb right now.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • wjplumbing
    wjplumbing Member Posts: 7
    Lochinvar wants the co below 150 ppm. Usually when I back out the Venturi screw the co climbs up.
  • NYplumber
    NYplumber Member Posts: 503
    What is the incoming gas pressure at static, at 100% and at 20%?
    It could be the regulator isnt locking up properly, or the regulator/meter setup is 5-10 larger then the boilers max input. To me it sounds like the mixture is rich on low fire and the only way you can compensate is by giving it air. If all checks out, try running a new intake in one size larger pipe diameter.

    Keep us posted.
    :NYplumber:
  • Ironman
    Ironman Member Posts: 7,552
    wjplumbing said:

    Lochinvar wants the co below 150 ppm. Usually when I back out the Venturi screw the co climbs up.

    Naturally, it's gonna go up. Just keep doing it til the foghorning stops and you're still within specs.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Ironman
    Ironman Member Posts: 7,552
    Just to put things in context: I posted about this problem here about a year ago and tried everything that has been suggested and more about venting, gas regulator distance, etc. None of it changed anything. Backing out the throttle screw to allow the highest acceptable co2 has cured it on every one that had the problem.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    SWEI
  • wjplumbing
    wjplumbing Member Posts: 7
    Thanks for the info gentleman. I will be heading to the job on Thursday and will keep everyone posted. Thanks, Jim.
  • wjplumbing
    wjplumbing Member Posts: 7
    Got the rep coming out today. Last night I maxed out the co2 to 9.8% with a co of about 140 ppm at high fire. I maxed out the co2 to 10.1% on low Fire with a co of about 35ppm and it did quiet down greatly. All numbers are within spec. We will see what the rep says. Jim
  • wjplumbing
    wjplumbing Member Posts: 7
    Drilled the 1/4" hole right above the intake 90 in boiler also .
  • wjplumbing
    wjplumbing Member Posts: 7
    Well met with the rep and they wanted me to adjust the unit to have more excess air. My settings only allowed 13% excess air and they wanted at least 20%. Right now it is running pretty quiet, with only a 1 second soft foghorn down from the 30 second loud one. Just don't know why this one has been a **** to quiet down. Just installed a whn 110 at my neighbors house and it is quiet as a mouse. I feel like I am rolling the dice when buying and installing a whn 85

    Jim

    Jim
  • Zman
    Zman Member Posts: 7,611
    I hate to see you adjusted that far out.
    Sometimes a very similar sound is caused or exaggerated by harmonics coming though the gas line. The gas line was short like yours.Replacing the regulator at the meter solved the problem.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • icesailor
    icesailor Member Posts: 7,265
    edited December 2014
    My take is that unless EVERY Lochinvar WHN 85 "Foghorn's" like yours does, the Rep is looking for "Air Answers", Solutions grabbed out of the air to try to resolve a problem that they don't know how to resolve.

    Way back when, some Munchkins were tooting their foghorns. Some of us discovered that they backfired into the swirl plate.

    The only WHN 85 I've ever seen is in a photograph.

    Did you try disconnecting the air intake from the boiler to see if the sound changed?

    Is it vented in 2" or 3"? If three inch, did you try restricting the exhaust where it ends up outside with a 3" X 2" Bushing?

    Did you find anything that changed the blow of the horn?

    When the Rep's can't fix them, then you REALLY start to learn. Because, when I needed help, I found that if I called ME, I could "Get'r'done". And ask here. No matter how stupid the question may seem to you, it never sounds stupid to me. I've asked a lot of stupid questions. But I learned the most from perceived stupid questions, asked of me, that I had to work hard to answer. That's when WE learned.

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