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noisy knight

JBW_2 Member Posts: 67

Actually found a propane conversion kit bag with the literature that was empty??
Have you installed this boiler before?? Is this standard?

Thanks for the prompt response.



  • JBW_2
    JBW_2 Member Posts: 67
    noisy knight


    I have just installed the Lochinvar knight KBN150 in a home in Montreal. Done a few installs of this boiler already.

    The other day, when I started it up, it started to really make a terrible reverberating noise. It kind of oscillated louder quieter, louder, quieter, and then just stopped. So, after reading the troubleshooting manual, I adjusted the venturi screw to the left and to the right to make it stop. I then checked my combustion, and found that my O2 was up at around 8-9 and my CO2 was at around 7-8.

    SO, in attempting to get at least within 10% of the recommended values I readjusted the venturi slightly. However, the closer I got to being within range the following began to happen:

    Prepurge, ignite for about 2-3 seconds, postpurge. I couldn't get the thing to stay lit. So I went out of the recommended CO2 and O2 levels, just to get the thing to light. However, when it lights, it makes a slight reverberating noise and I can hear the venturi whistle for about 1 split second right before start up. I received a call this morning from the owner that the thing was reverberating all through night.

    I checked my gas pressures and everything, but all is well. I dont know where to go from here. Either the thing is noisy as hell or it doesn't light.

    Has anyone had a similar experience?? I called lochinvar and they recommended adjusting the venturi adjustment. But this is obviously not helping.

    My exhaust and intake lengths are way less than 100 equivalent feet and my slope is good. I even tried running the thing with exhaust and intake air completely disconnected. I also investigate the exhaust chamber (clean) and the intake all the way to the gas/air mixing point (also clean). I was thinking either change the gas valve or combustion chaber may be restricted. Condensation is good and so is system and boiler pumps.

    Please contact me if you have any suggestions. I am waiting until monday to call Lochinvar. I waited on hold for over an hour while I was tweeking the boiler today.


  • tim smith
    tim smith Member Posts: 2,752
    Noisy combustion

    Verify that correct size orifice is in unit if there is one? Maybe a mfr error. Just a thought
  • don_52
    don_52 Member Posts: 199
    noisy knight


    You may have answered your own question, a quick look at
    the settings in section 10 and what you have set ( to make
    it work ), would lead me to believe. A. The mixing valve is
    fubar. B. Wrong orifice, (LP vs NG), since everything else

    Wouldn't be the first time that happened.

    Seen this happen when fuel/air linkages got stuck, sounded
    like a buzz bomb.

    Something to consider, yeah I know, PITA to disassemble,
    think about it.

  • JBW_2
    JBW_2 Member Posts: 67


    Actually, after looking over conversion instructions realized that the brass orifice was in the conversion kit package. I will definitely take apart the gaz valve and check the orifice size. This will also allow me to see if the orifice is slightly blocked.

    Thanks all for the advice.

  • Uni R_2
    Uni R_2 Member Posts: 589

    Would increasing the minimum fan speed slightly cure it? Does it start making this sound at ignition speed or after it ramps down to minimum modulation?
  • JBW_2
    JBW_2 Member Posts: 67

    is there a way to do this?

    Checked the manual, didnt see anything...
    BTW how thick is the orifice?
  • don_52
    don_52 Member Posts: 199


    This, IMHO is both the blessing and the curse of these
    small modcons, one adjustment, some have a low fire zero-
    offset + high-fire span.

    Page 40 & 41 of the service manual is pretty much it,

    Vent/Air Intake Length or Obstruction, OK
    Gas Supply Pressure, OK
    Dirty/Damaged Burner, OK?
    Gas Valve Adjustment, No Joy!
    Confirm Correct Orifice as NG, suspect is NG

    You already did all that;

    Punt, Call Factory Replace Gas Valve?

    It's not like having a larger packaged/skid mounted unit
    with an AutoFlame that you can actually "tweak", you'd be
    done and gone.

    Everything is "characterized" at the factory against
    flue temp/fan speed/orifice size and the "electronics"
    leaving one sloppy little (backlashing) screw to set
    the fuel/air ratio and most of the time it does work

    Harmonics? I don't think so, course I'm not there, so moot

    Hot Rod has done a bunch of these hopefully he'll see
    this thread and share some insight.

    Good Luck, B-Safe, db
  • Greg Gibbs
    Greg Gibbs Member Posts: 75

    Josh, are you going to be back at the job today...if so try
    firing to boiler w/ the intake air pipe removed from the boiler (Use the room air for combustion)... Do this just for a minute. If that does not allow the knight to run "smooth" check the intake for blockage...I had two Knights last week, one w/ a bird in the intake, and the other had a pc. of batt insulation that was stuffed into the makeup. I know you stated that you checked the vents,
    but the bird and the insulation had made it all the way to the fan!
    Please let me know what you find...Greg Gibbs
  • what did you find?


    i've supplied over 150 of these and never had this problem.

    What have you found out?


This discussion has been closed.