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Lochnivar Noble low flame at high fire

roberto764
roberto764 Member Posts: 6
in THE MAIN WALL

I just installed a new Lochnivar Noble NKB199N boiler. It has been converted for propane.

On low fire the flame signal reads 11.3uA

On high fire the flame signal reads 7uA


The manual states it should have a flame signal of at least 10uA.

Gas pressure is 12.12” wc at lockup and 10.17” wc at high fire.


I have about 100’ of 1/2” pipe from the primary regulator to the secondary regulator and 8’ of 1/2” pipe plus 4’ of flex line from the secondary regulator to the boiler.


Why would I be getting a lower flame signal on high fire than on low fire? I would think my gas supply is adequate as it’s not dropping below 8” wc on high fire. I took everything apart to make sure there were no obstructions in the air piping or burner and even cleaned the flame sensor which changed nothing. I even changed the gas valve thinking maybe it was that and nothing.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 18,830

    I don't know what Lochinvar requires for gas pressure on HF. Was the boiler set up properly with a combustion test done.

    In one sentence you say gas pressure is 10.17" at HF then you say it does not drop below 8".

    Can you clarify?

    Where are you measuring the gas pressure?

  • roberto764
    roberto764 Member Posts: 6
    https://forum.heatinghelp.com/discussion/comment/1868106#Comment_1868106

    For propane Lochnivar states 14” max and 8” min. That’s what I was referencing when I was stating I am not dropping below the 8” min that Lochnivar specs. Measuring gas pressure on the test port on the gas valve.


    Yes ran combustion and tuned it with it the manual specs.

  • pecmsg
    pecmsg Member Posts: 6,582

    what were the combustion numbers?

    hot_rod
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 18,830

    Well operating at 8" is at the factory minimum but being at the minimum leaves you 0 margin for any changes. Combustion is not an exact science.

    As the weather changes temperature the density of the combustion air changes with the temp. And other things such as the temperature of the fuel and the btu/cubic foot of gas can change slightly.

    You might try bumping the gas pressure up a little and see if that helps. With propane you have no gas meter to verify the boiler input. You only have the gas pressure to go by

  • roberto764
    roberto764 Member Posts: 6
    https://forum.heatinghelp.com/discussion/comment/1868112#Comment_1868112

    I don’t have them with me I’ll have to check tomorrow. Went by what the manual called for as you can see in the photo. The only thing I can remember off the top of my head is that the CO on high fire was right around 158ppm

    IMG_5732.jpeg
  • roberto764
    roberto764 Member Posts: 6

    High fire running at 4.2% o2 and 11.03% co2


    Low fire running at 5.2% o2 and 10.37% co2


    Talked to Lochinvar tech support and they said as long as the flame signal is reading above 3uA it should be fine. I just thought it was strange that it would have a lower flame signal on high fire compared to low fire.

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