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How rich is too rich

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Driven11
Driven11 Member Posts: 13

Battling the HTP phoenix lite that I've named "tuba". Foghorns like a sonofa for the first 30 seconds or so after ignition. I tried all the usual suggestions and the only thing that works is throttling a little rich. It's out of spec though. Manual calls for 8-10% for low and high fire. I keep low around 8.5 for some excess air to keep the burner cool but high is closer to 11 if I want silence. Maybe a little more. CO stays well under 60 so I don't know if I should even care as it's more efficient combustion the higher that CO2 goes. I've searched and searched and nobody ever has a real answer to all the modcons that howl besides richen it up.

Comments

  • mattmia2
    mattmia2 Member Posts: 17,355

    co of 60ppm seems kinda high, you are probably on the low excess air side of the curve.

  • Mad Dog_2
    Mad Dog_2 Member Posts: 8,660

    I'm not sure where you operate out of, but in New York, the Natural Gas Utilities want CO flue #s under 50 PPM as a rule. Mad Dog

  • HVACNUT
    HVACNUT Member Posts: 7,518

    Each manufacturer has their own specs on CO in the flue. Most want <100 ppm CO. Some like the NTI Trinity allow up to 175 ppm CO in the flue. Not saying its right, but…

    Mad Dog_2
  • Jamie Hall
    Jamie Hall Member Posts: 27,564

    You probably aren't confused, but I've seen it enough times to feel a need for a caution: CO and CO2 are not the same thing. And in combustion work in general, CO will increase with a richer mixture, while CO2 will increase with a leaner mixture.

    Another sort of useless general comment: sometimes you can get a resonant sound — like a tuba maybe! — from unstable combustion, but other times you can get a similar sort of sound by simply varying the air flow — and it may change as less air or more flows through. This can be altered by draught, for instance. Or of course any air shutters.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ironman
    Ironman Member Posts: 7,922

    Is any portion of the gas line CSST?

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    HydronicMike
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 12,484
    Screenshot 2026-06-11 at 10.22.31 AM.png

    This is certainly not Too Rich

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Alan (California Radiant) ForbesDriven11
  • Driven11
    Driven11 Member Posts: 13

    Only the 6" piece HTP uses inside their control panel. Completely hard piped.

  • Driven11
    Driven11 Member Posts: 13

    I agree but also hear comments like "anything below 100 is fine". What else can I do besides have the noise? And why does it only happen for that short time at ignition? You'll find 100s of these type of threads with a quick Google search but none of them ever seem to have a detailed, proven explanation. Some say pipe, some say vent, some say regulator, but when those items are changed it never seems to solve anything.

    Alan (California Radiant) Forbes
  • mattmia2
    mattmia2 Member Posts: 17,355

    there are 2 places where you can get the same CO2 value. you are on the left side, you want to be on the right side.

    image.png
  • Driven11
    Driven11 Member Posts: 13

    Yes I'm on the right side 100%. I thought of that. The readings verify based on my gas adjustments. I'm between 3 and 4% O2 currently.

  • Jamie Hall
    Jamie Hall Member Posts: 27,564

    Just a thought — but have you tried going way lean? Just enough fuel in the air to fire up? and then adjusting back richer? Until the CO2 peaks and the CO maybe beings to show an increase?

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Driven11
    Driven11 Member Posts: 13

    Not sure what you mean. just to verify I'm on the right side of the curve?

  • leonz
    leonz Member Posts: 1,854

    I thought for a minute there you were talking about the 15+billionaires in the cargill and mcvey families😀

  • Driven11
    Driven11 Member Posts: 13

    How many years before you can't plant corn in your garden without kicking up to them?