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Help needed to troubleshoot boiler

Treebeard
Treebeard Member, Email Confirmation Posts: 18
edited October 2021 in THE MAIN WALL
Old MZ boiler. Mechanic changed gas valve and it works well except it is still failing to stay lit. The flame comes on for a few moments (about a second). Any ideas what needs replacing now?

Comments

  • HVACNUT
    HVACNUT Member Posts: 6,053
    Treebeard said:
    Old MZ boiler. Mechanic changed gas valve and it works well except it is still failing to stay lit.  Any ideas what needs replacing now?
    I give up... the mechanic? 

    What's an old MZ? Model number?
    Pics?
    Wiring diagram?
    STEVEusaPA
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,092
    @Treebeard

    was this a flooded unit?
  • Treebeard
    Treebeard Member, Email Confirmation Posts: 18
    This is a condensing boiler which has been maintained for many years. The water is in a sealed loop, and the pressure is correct. The boiler will work for hours or days without a problem and then it will flame-out. The mechanic said it was a bad gas valve and replaced it. Weeks later the boiler is doing the same thing. No strange sounds, just ignites the gas, then the flame goes out.
  • Zman
    Zman Member Posts: 7,609
    edited October 2021
    Where are you located? Your model may not be sold in the US.
    It is likely the boiler is not "proving" the flame. It also sounds like the "mechanic" is a parts changer rather than a troubleshooter. That can be an expensive road. Was a combustion analysis performed when the gas valve was changed?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    HVACNUT
  • Tomato
    Tomato Member Posts: 21
    Perhaps they mean this one?

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