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Lochinvar ignition trouble

JCattles Member Posts: 1
I have a lochinvar knight kbn150, it was installed in 2006 and ran flawlessly until now.

The boiler fails on ignition, I have removed and cleaned the burner, cleaned the heat exchanger, replaced the flame sensor. I have tested gas pressure with a manometer, I have 9"water at inlet, at outlet side of gas valve I get about 8" negative during purge and then it goes to -2" when fan slows, when gas valve opens I get zero. I can see the spark through the sight glass when it attempts to fire, no flame.

I even got on a ladder and smelled the air exiting the exhaust when the boiler purges after ignition trial and can smell gas. I am dumbfounded, I have fuel, I have spark, but no flame!

All I can think of is the gas valve isn't allowing enough fuel by during ignition, but that seems unlikely and I don't want to drop that much money on a hunch.

Any ideas?


  • Snowmelt
    Snowmelt Member Posts: 1,418
    Call tech

    There might be some kind of over heat cut off fuse that might be tripped, or a high limit, I know when those two things happen on some product the gas valve won't even try to start.
  • Eric_32
    Eric_32 Member Posts: 267
    What's the error

    Whats the error your getting?
  • JStar
    JStar Member Posts: 2,752

    Verify the proper spark gap. Even if it sparks, the airflow may blow the arc off of the ignitor. You can also adjust the venturi ratio but will need an analyzer to verify the results.

    Is this direct vent or Category IV?
  • Burnertech
    Burnertech Member Posts: 6
    edited July 2014

    Remove the ignition cable from transformer on the board. Attempt to fire the unit. If the spark does not jump to the grounding post replace the board. If it does make the jump. Check the gap on your igniter. After that move towards valve adjustments ect.