boiler pressure at 30 PSI

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by suelue, Sep 14, 2013.

  1. suelue

    suelue New Member

    Messages:
    2
    Location:
    mukwonago, wisconsin
    Our boiler valve goes over 30 PSI - happened with our old one so we had it replaced. Have this one not even 3 years and doing the same thing. Any idea why the same thing would be happening again? Could the tank be bad in less than 3 years?
  2. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,225
    Location:
    Maine
    Bad or unpressurized expansion tank
    Auto fill valve improperly set or bad
    High limit set too high
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,815
    Location:
    Cave Creek, Arizona
    There are several possibilities, but none that we could diagnose without doing our own tests on the boiler.
  4. MACPLUMB 777

    MACPLUMB 777 TROJAN WORLDWIDE SALES RP

    Messages:
    679
    Location:
    Houston, Texas, United States
  5. suelue

    suelue New Member

    Messages:
    2
    Location:
    mukwonago, wisconsin
    This can be the problem even though it is all new?
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,129
    Location:
    New England
    If the expansion tank isn't sized properly or precharged to the needed level, it could allow the pressure to rise more than desired. But, it's more likely that the autofill valve is potentially leaking or incorrectly set. FWIW, an autofill valve can mask system problems, and you may want to just readjust the pressure to design, then (hopefully you have one) shut the water off to the autofill valve. If you have a leak, having it open can mask that to you. Constantly adding fresh water to a boiler is problematic, and you really want to know about it. IF you don't have any leaks, shutting the autofill valve will have no effect on the system operation. If you do have a leak, instead of creeping up, it will gradually drop as water leaks out, eventually tripping the boiler's low-limit safety device interlock.

    If it's something else, it's still a good idea to shut the autofill valve and you'd have eliminated one of the possibilities.
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