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Lochinvar nkc110

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njeichelberger
njeichelberger Member Posts: 8
edited October 2023 in Gas Heating
I am looking for any guidance on an issue I have been having with my unit for the past two years. The main code is Flame fail: ignition. It is random and sometimes will run for weeks without an issue but then some weeks it will happen daily. It seems to get better in the summer and worse in the winter. I have performed all the steps in the manual on troubleshooting this problem. The only thing that I currently am able to tell when it is running is that at 100% run the flame is 7.0-7.5. From my understanding, this is too low but I am at a loss as to what I should do next.

Parts replaced:
Gas Valve
Ignitor - (Twice)
Ignitor wire
Main computer board

Tested
Cleaned the whole unit
Checked the burner
Cleaned the blower and checked for any obstructions.
Checked grounding of the unit
Checked propane pressure (11.5 normal 10.5 while running)
Checked O2 and CO2 levels. They were within specs


Appreciate any thoughts or suggestions.

Comments

  • Alan (California Radiant) Forbes
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    Your gas pressure sounds fine, but I would check it when other appliances are on.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    ZmanGGross
  • 109A_5
    109A_5 Member Posts: 1,387
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    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • njeichelberger
    njeichelberger Member Posts: 8
    edited October 2023
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    We checked all ground wires for continuity. They were all functioning properly as far as we could tell. 0.02 so did not have a short and we did have continuity. I will also take measurements when using the propane stove. This is the only other propane appliance in the house.

    Edit:
    Just checked the pressure with the stove and oven running. It was basically the same.
  • HomerJSmith
    HomerJSmith Member Posts: 2,467
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    Was a proper LP conversion done? Do a combustion analysis.
  • pedmec
    pedmec Member Posts: 987
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    what is 7.0-7.5?

    i would check combustion. normally when you have an issue that is getting affected by temperature changes it is related to your air/fuel ratio. cold air is more dense than warm air.

    what you do next is pay for a combustion analysts from a professional
  • GroundUp
    GroundUp Member Posts: 1,924
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    The only times I've seen this happen in a Noble is improper gas valve setup, usually on low fire, or exhaust gas recirculation. The low vA of the flame sensor is almost always because it's dirty, typically due to the aforementioned poor combustion and/or EGR. What are the actual co2 readings at both low and high fire? How long is the vent and what diameter is it? What size gas line and how far from the regulator?
  • njeichelberger
    njeichelberger Member Posts: 8
    edited October 2023
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    @GroundUp The gas valve was recently replaced to test that. also, the ignitor was replaced less than 4 months ago just to double-check that. The CO2 and O2 readings at high fire were 10.0 CO2 and 5.9 O2. So right on the edge. The vent is 3 inches and is about 3 feet total with a 90 and a 45. So from my understanding, this should be fine. Just for fun, I added another 2 feet to each yesterday to see if it made any difference, but it did not. The gas line is 1 inch and about 40' from the regulator. I have not observed a loss in pressure over time though. Each time I check it, it is at 11.4 and then 10.4 when running.

    Also the LP conversion was done
  • Zman
    Zman Member Posts: 7,572
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    Is the boiler pulling combustion air from outside or from the space? What was the outside air temp when the combustion analysis was done? Did they check it at high and low fire? Is there a reason that they did not richen up the mix a bit? I suspect that you are running too lean.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    HomerJSmith
  • njeichelberger
    njeichelberger Member Posts: 8
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    It is pulling the air from outside. The test was done yesterday and it was 50 degrees out. Although this failure has happened at all temperatures ranging from 0-70. Just for fun/to test, I ran it with it pulling air from inside the garage and the flame reading went up to 8 instead of 7... but this is still too low. As far as trying to make the mix more rich, is the only way to accomplish this using the throttle control on the unit?
  • Zman
    Zman Member Posts: 7,572
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    Someone with a combustion analyzer should adjust the throttle (and maybe the offset with the blessing of tech support) per the manufacturer's service manual. The combustion should be checked at both high and low fire.
    If they did not check it at both high and low, the combustion may be way off some of the time and that may be causing your issue.
    Can you recall if they checked it at high or low? Any mention of the CO reading?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • 109A_5
    109A_5 Member Posts: 1,387
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    Hello @njeichelberger,
    As much as you checked the Grounds and it may be a flame quality issue, mixture or flame shape at the flame sensor rod, what they don't say here is;
    The Ground path has to also be intact through X1-8 to the Control Board since the Control Board is doing the current monitoring. And sometimes wires are missing from the factory or get disconnected from service efforts and are not connected properly.






    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • njeichelberger
    njeichelberger Member Posts: 8
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    Here are a couple of photos with the low and high burn. Also, the ground wires are in the proper spot after double-checking. The low burn has lower O2 and higher CO2






  • 109A_5
    109A_5 Member Posts: 1,387
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    Hello @njeichelberger,
    Interesting your flame signal is just the opposite of what the manual implies.

    At least it will go over 10 microamps (11.6 microamps at 25%), so probably not an electrical issue.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • CPHNed
    CPHNed Member Posts: 14
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    What altitude is boiler installed at?
    Lochinvar has recently changed computer boards for high altitude installations.
  • njeichelberger
    njeichelberger Member Posts: 8
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    Altitude of 350'
  • GroundUp
    GroundUp Member Posts: 1,924
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    You have confirmed my suspicion. The combustion is WAY off. Low fire is 10%, not 25%, and you need the CO2 up around 10.4-10.5% at low fire. High fire should be 10.5% to 11%. Also, I have found that the venting should be 2" when that short despite what the manual says. I'll bet it's also making some weird sounds at certain firing rates as well, like a foghorn or howling sound? The ignitor will dirty up in just a couple days with combustion like this, so that should be replaced again or at the very least, cleaned. Get that combustion tuned properly and you'll be well on your way.
    Alan (California Radiant) Forbes
  • Zman
    Zman Member Posts: 7,572
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    If your tech is not paying attention to CO, he/she is not paying attention...
    FYI, that analyzer is only measuring 02, CO, and air temp. Everything else is calculated.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • njeichelberger
    njeichelberger Member Posts: 8
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    Working on a couple of these items but will update once that has been done.
  • pedmec
    pedmec Member Posts: 987
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    One other thing to look for is the venturi. Make sure that the the venturi that is in the boiler is for propane. I have seen a lochinvar 500k ftxl run with the wrong venturi but it wasn't running well. Don't know how a Noble 110k will function with the wrong venturi but it's something to look at just to eliminate it from the equation if it is a the correct venturi. i kind of think this might be it because your high fire flame signal is weaker which is opposite of what would happen with the correct flame pattern. Your flame pattern has changed significantly in the opposite direction of whats suppose to happen
  • njeichelberger
    njeichelberger Member Posts: 8
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    @pedmec just checked to make sure but it is the correct venturi