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boiler blow off

cccx3 Member Posts: 1
boiler keeps blowing off at 30 lbs new fill valve set at 10 lbs new relief valve 30 lbs new expansion tank new aquastat. Furnace shuts off at 180 temp but lbs goes to 30 have a pressure gauge before expansion tank shows pressure water in at 10 lbs but goes up to 30 expansion tank has 15 20 lbs pressure in it


  • Zman
    Zman Member Posts: 7,569
    Blow off

    Does it happen with the fill valve isolated?

    Do you have an indirect tank or coil that could be leaking high pressure domestic water into the system.

    Is the expansion tank sized correctly?

    Did you check the tank pressure when it was detached from the system?

    A picture of the piping arrangement would help.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • remodel
    remodel Member Posts: 68
    might be this

    read through this wall posting touched most of it: