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Lochinvar Knight boiler that sometimes makes a loud singular BANG, upon firing up

akmichaelakmichael Member Posts: 2
Hello All,
I have a Lochinvar Knight boiler that sometimes makes a loud singular BANG, upon firing up.
It is very similar with the thread from aksteveex from March 2017 in Gas Heating. Ironman had the most helpful information so far.
I too, am in Southcentral Alaska. Our contractor is very knowledgeable, and was her last month for the annual (thorough) cleaning and service. When I described what we hear from time to time, he thought it was from the silt we get in the area. In my opinion that is not the case now, as we have had a constant snowcover since before he cleaned it.
Some might question from the other thread about zone valves. The noise I have heard is during firing. Sometimes it will go weeks or months, but happened twice yesterday, and once this morning.
Any assistance would be greatly appreciated.
I will call our service folks tomorrow, and ask them, but seeing if others might have a solution.
Thank you.


  • DZoroDZoro Member Posts: 565
    Will need to check incoming gas pressure, steady state and operating pressures.
    Clean heat exchanger.
    Need combustion analysis done, and set to factory recommendation.
    Check igniter
    Confirm intake and exhaust piping is correct, no blockage with snow.
    All or any of these can cause the delay in ignition which is what you are experiencing.
  • akmichaelakmichael Member Posts: 2
    Thank you for the reply.
    The first thing we check is the intake and exhaust, after a service call last year for no heat.
    The service was completed 11/27/18.
    Cleaned heat exchanger. Replaced igniter and flame sensor.
    Going to check the other items you suggested.
    Thank you.
  • DZoroDZoro Member Posts: 565
    Make sure they have a combustion analyzer and bring it.
    If they don't have or know how to use/set up with it find someone who does.
  • rick in Alaskarick in Alaska Member Posts: 784
    What part of South Central are you located in? If you are near Kenai, I would contact Whites plumbing. They know there stuff! If you are more south of Kenai, It might be in my area and I can check it out.
    It sounds like a delayed ignition problem, which might be an ignitor that is not sitting quite right.
  • gennadygennady Member Posts: 722
    Looks like you describe delayed ignition. Check electrodes settings they are probably off. Or better replace them. Check at what speed it is set up to ignite. Usually 40-50% for these boilers. Check gas pressure and gas to air ratio. Check venting for restriction.
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
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