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issue with converted gas power burner

zepfan Member Posts: 390
We are having an issue with a Crown boiler that was originally oil fired. Model # CTPB-8 manufactured in 2003, converted to natural gas in 2017. That part was done by others. The unit has a Carlin ez pro gas burner control installed on it. The boiler has an identical model installed next to it that vents into the same chimney. That boiler which is the same model operates with no issues. The one with the issue comes on, proves flame, but then after about 10 seconds it sputters out, almost like it is back firing then loses flame. The heat exchanger is sealed and operates at a slight positive pressure about .01, where the stack pressure before the barometric damper is -.03. These readings, positive over the fire and negative in the stack is the same on both units. I removed the flue pipe check it, and the heat exchangers and both are clear and un obstructed. Also both the gas inlet pressure before the valve, and going to the burner are the same on both units. Any assistance/recommendations as to what could be causing this back firing/ sputtering out on the one unit would be greatly appreciated. Thanks to all


  • Big Ed_4
    Big Ed_4 Member Posts: 2,534
    edited October 4
    Seems from here for the moment the problem is fuel supply problem , gas pressure readings will be needed . From the hip does the problem burner run ok if the sister unit is off ?
    I have enough experience to know , that I dont know it all
    Mad Dog_2zepfanMikeAmann
  • Steamhead
    Steamhead Member Posts: 16,459
    Run the burner with a pressure gauge connected to the downstream tap on the valve and your combustion analyzer set up and running. Does the gas pressure stay the same? Does the fuel-air mix stay the same?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Mad Dog_2zepfan
  • zepfan
    zepfan Member Posts: 390
    Thanks for the responses Normally the boilers do not run in tandem. The controller stages them and the first stage is set for lead/ lag, so this problem is present with the sister boiler off. I connected a manometer to the inlet outlet ports on the gas valve, and the pressures seem constant the whole time this issue is occurring. 11” in 3.6” out unless the valave is sticking so fast that the meter can’t pick up the pressure fluctuation. Thanks again
  • zepfan
    zepfan Member Posts: 390
    If there is way to post videos I can post a video of this condition, I did not see a way to do that
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,736
    To post a video, you need to post it on YouTube and post the link to that video. If you don't have a Youtube video account it is easy to make one. Just google the instructions. I used a FaceBook link to post a video on this site years ago, but that facebook account is long gone since my company was sold and I retired. (or I could tell you how to post a facebook video... But I need a millennial to do that for me since I'm a Boomer)
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    Erin Holohan Haskellzepfan
    HVACNUT Member Posts: 5,476
    You're getting 11" lockup with nat gas?
    Seems high. 

    The orifice is drilled the same size as the other burner?
    The Flame rod is clean and Not touching any metal through the diffuser plate?

  • zepfan
    zepfan Member Posts: 390
    Thanks for all that responded to this. It turns out that making a slight adjustment to the air shutter from 70% to 80% made all the difference. The burner lite off smooth, and after running for a while, I did a combustion test ,and the readings and stack draft were good. The boiler is 256 mbh in, and while the instruction manual called for 70 %, it had to be set at 80% in order for the burner to stay online. Thanks to all