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"Tuning" a Gas Oven for Low CO Emission

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  • "Tuning" a Gas Oven for Low CO Emission

    Does anybody have a step-by-step procedure for this?

    My new Jenn-Air range running on propane has flame problems in the baking mode only. (Top burners and broiler behave fine.) The propane conversion was done, apparently to spec. Symptoms are a very noisy flame and high Carbon Monoxide production (I mean REALLY high -- in excess of 1000 ppm from the exhaust ports, as measured with my new Fluke CO-220 meter) only for the first several minutes, until the oven gets pretty hot. The noise and CO are accompanied by an acrid smell (unburned hydrocarbons?). Both the noise and the CO production subside to "normal" (below 100 ppm) after several minutes, although the oven is still heating. (Don't worry, I'm running the hood blowers and ventilating the house so as not to kill myself. My CO alarms have yet to be triggered.)

    I've had the dealer's service man out once. He removed the warming tray underneath, took off some sort of shield over the gas-mixing apparatus, took up the "bottom plate" of the oven, and showed me (from above) a flame that was pulsating and igniting well away from the holes in the burner. He said this was caused by too lean a mixture. He partially closed the air intake (which was full open) so that the flame looked and sounded much better. Then he put the bottom plate and the underside burner shield back on and everything seemed OK. What he DIDN'T do was let the oven fully cool before re-testing.

    Next day I still have the same symptoms whenever the oven is cold, sometimes with only 200-400 ppm of CO initially, decreasing to around 50 ppm after 2-3 minutes, but other times as bad as ever, the higher CO production always coinciding with a noisy flame (which of course I can't see in fully assembled condition). Further, the performance of the oven burner seems to be significantly affected by opening and re-closing the oven door. At least once a quiet flame and low CO production have been reversed (or vice versa) just by opening and closing the door.

    Obviously I have several questions:

    1) Does it make sense that an initially noisy flame and high CO production resolve as the oven heats up? If so, why?

    2) Does it make sense that flame behavior is significantly different fully assembled vs. disassembled? Is there a straightforward tuning procedure under these circumstances, or...

    3) ...Do I have to iterating gradually toward best performance, disasembling so I can see the flame, adjusting the air intake a little, re-assembling everything, waiting for it to cool, and then re-testing?

    4) Should I be adjusting for best flame when the oven is cold or hot?

    5) Does the erratic change in behavior from time to time, or occasionally on opening/closing the oven door, suggest anything at all.

    I need to get this problem resolved before winter, when adequate ventilation will be less acceptable. Any suggestions (or recommendations of other information sources) will be greatly appreciated. -- JClarkW

  • #2
    Less fresh air into oven until it is hot?

    Is there less airlfow out of the oven until it heats and increases draft?
    Such may be limiting fresh air getting to the burners and cause already combusted air to be recombusted, producing more CO.
    Somewhat closing the air into the burners, therefore diminshing O2, would increase CO production.
    Is the propane gas pressure too high?
    Were the proper orifices installed?
    I'd take an educated guess - but I'm unqualified.
    It ain't just soot, it's paydirt.
    "I swear, wherever Gift goes, argument follows." -Youtube comment

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    • #3
      Re: Less fresh air into oven until it is hot?

      check for spider webs or insect nest in the air supply or in the burner,

      (I had a grill that would not work in the spring or ti would burn eradicate, as spiders would make nest and lay eggs sacks in the air intake of the burner,

      but it also sounds some like you have more gas than you need as well, (could just be an air problem), I would think rechecking the orifice would not hurt,
      and possibly putting a low pressure gas pressure gage (manometer) on the line and see if the gas pressure is correct and steady
      Last edited by BHD; 10-08-2012, 11:19 AM.
      Push sticks/blocks Save Fingers
      ~~~~~~~~~~~~~~~~~~~
      "The true measure of a man is how he treats someone who can do him absolutely no good."
      attributed to Samuel Johnson
      ~~~~~~~~~~~~~~~~~~~
      PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

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      • #4
        Re: "Tuning" a Gas Oven for Low CO Emission

        >>Is there less airlfow out of the oven until it heats and increases draft?<<

        This is almost certainly true, but what to do about it? Should I be tuning the oven for preheated conditions and just sucking up the CO produced during warmup, or the reverse?

        As for the orifice, according to the "qualified" repair man (who showed up without a CO meter -- I made him use mine) it is as specified for propane at my altitude (6100 ft). Neither the service man nor I has checked the propane pressure, but the propane furnace (on the same line) is happy. (Or is it the case that each gas appliance has its own regulator, in which case what pressure is the main regulator on the propane tank supposed to deliver?)

        >>check for spider webs or insect nest in the air supply or in the burner,<<

        This is a brand new oven.

        I don't understand all the issues, but if the oven is getting too much gas (whether from an overlarge orifice or from excessive gas pressure), can't you compensate by just opening the air intake further? (The service man set it at about 50% to get the best flame with the cover plates removed.)

        But my real question is, "How you are **supposed** to tune an oven?" In my mind this has most to do with the change in behavior during warmup and between fully assembled and opened up for tuning. What is the recommended procedure?
        Last edited by JClarkW; 10-09-2012, 04:43 PM.

        Comment


        • #5
          Re: &quot;Tuning&quot; a Gas Oven for Low CO Emission

          First I am no expert, all I have ever done is my own work, (so use what your read at your own risk).

          but I would think you would want to set for when it was in a warmed up and working mode, ( I would not think there should be a dramatic difference, if it is set up correctly and working correctly, tho ),

          at 6000 feet the orifice would need/should be down sized, from the standard "sea level" unit,

          and it is my understanding most just use the flame color to adjust the air, Info at link, the LP will or may have slightly yellow tips, where NG should not , but they should not be excessive,
          Appliance411 FAQ: What should my gas range's flames look like?

          the pictures, the blue flame is "correct" and the yellow is not.

          I have read that with to much air the flame will lift off the burner,

          Incomplete Combustion
          When propane gas does not completely burn it produces carbon monoxide. Incomplete combustion occurs when the ratio of propane to air is less than four parts propane to 96 parts air. You can also notice a lean burn when the flames appear to go out from the propane burner or lift away. A rich burn also causes incomplete combustion, as there is too much propane in the propane-to-air mixture. A rich burn occurs when the flames of the propane are very large and yellow


          Read more: The Dangers of Propane Burners | eHow.com The Dangers of Propane Burners | eHow.com


          IS there a factory help number you can call for better advice, on that unit,
          Attached Files
          Last edited by BHD; 10-10-2012, 11:04 AM.
          Push sticks/blocks Save Fingers
          ~~~~~~~~~~~~~~~~~~~
          "The true measure of a man is how he treats someone who can do him absolutely no good."
          attributed to Samuel Johnson
          ~~~~~~~~~~~~~~~~~~~
          PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

          Comment

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