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Hydronic Gas Boiler high pressure issue



  • MikeAmann
    MikeAmann Member Posts: 714
    edited November 2022
    @neilc @Jamie Hall @pedmec @hot_rod
    The tank needs to be at or near the inlet if the circ. If the circ was on the supply after the air purger, then the tank would be fine under the purger.
    Got it. That makes sense. And yes, pumping into the boiler.
    Here are the additional pics:

    It's all done and working the way it should. So far it looks like the pressure now varies between 12 and 18 psi.

    EDIT: CORRECTION - system pressure varies between 5psi cold to 24 psi hot. It's like the exp tank is not even there.
  • SuperTech
    SuperTech Member Posts: 1,888
    @MikeAmann that green 007 shouldn't be installed motor facing up like that, it's in the installation instructions.  It could easily trap air and burn out the circulator motor. That was the craziest description of a way someone installed an expansion tank that I have ever heard. Putting the tank into a vacuum? Pre filling with water? I would drain it back down, correct the circulator installation, correctly pre charge the tank and tie in the fill valve to the expansion tank location. 
  • unbelievable21
    unbelievable21 Member Posts: 10
    so to recap as OP, my issue is because water regulator/feeder is before the circulator and not on the supply side before exp tank? It has been like this for 20 years and never had high pressure increases like it is now. I should move feeder with backflow to right before exp tank?
  • unbelievable21
    unbelievable21 Member Posts: 10
    edited October 2022
  • MikeAmann
    MikeAmann Member Posts: 714
    I think @neilc nailed it with this description for your problem:
    the system pressure at the tank doesn't change*,
    when the circ pumps towards the tank, the inlet of the circ is a lower pressure than at that the tank,
    if your feed is before the circ, the feed sees that lower pressure, and compensates raising the pressure into the circ, to the preset 12~15,
    now on the outlet of the circ, (incorrectly pushing into the tank), that pressure rises, taking up some of the tank air cushion, and you raise the entire system pressure all the way thru the system, until the feed into the circ is back up to the preset 12~15, note that you're now seeing 20~25, or whatever, on the circ discharge side,
    and have now raised the entire static system pressure (the pressure when the circ is off) to the 20 you're seeing,
    * doesn't change unless the circ pulls on the inlet and feed as described above.
  • pedmec
    pedmec Member Posts: 718
    I think that was stated multiple times in the post including by yours truly
  • MikeAmann
    MikeAmann Member Posts: 714
    Yes, it was. I just wanted to help get unbelievable21's thread back on track, because I unintentionally ended up hijacking it.
    And now, back to your regularly scheduled program....
  • MikeAmann
    MikeAmann Member Posts: 714
    edited October 2022
    One small thing to add:

    Notice the picture on the label.
    This is why you can never "feel" the water level inside of the tank.
    You can only feel the water down to the crimp where the diaphragm attaches inside.
    Beyond that, the air cushion and diaphragm isolates the water.