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Pressure gauge jumping

wchevron Member Posts: 12
I've got a Munchkin boiler. In heating mode it runs fine. When it switches to domestic to heat the indirect, the piping starts making a noise and the pressure gauge jumps back and forth each time the noise happens. The indirect circulator is running and it seems to be making hot water because after a few minutes it's satisfied and the boiler turns off. Could the domestic pump be going? Just started happening tonight.


  • wogpa67
    wogpa67 Member Posts: 238
    Has that ever been serviced?
  • wogpa67
    wogpa67 Member Posts: 238
    Pics of piping always helps.
  • Snowmelt
    Snowmelt Member Posts: 1,404
    Sounds like air in the line
  • wchevron
    wchevron Member Posts: 12
    Just went down this morning, back in domestic mode and everything running fine?
    It's piped correctly, been running for 8-9 yrs. First time it ever happened.
  • icesailor
    icesailor Member Posts: 7,265
    If it runs fine (no jumping) in heat mode where it modulates or is modulating, and it switches to DHW mode, it switches to High Limit mode. Sounds like the flow is too low and it is flash steaming. Might be a dirty boiler, dirty HX or a primary circulator with impellor issues that have slowed the GPM's through the HX with the hotter water flashing to steam.
  • JohnNY
    JohnNY Member Posts: 3,226
    The water is boiling. You have a flow problem.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.