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bouncing pressure gauge

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  • bouncing pressure gauge

    i was doing building checks the other day.

    when i was in the boiler room i glanced at the pressure gauage was bouncing between 15 and 20psi.

    i checked the expansion tank by knocking on it and it sounds empty. all the valves are open to the tank.

    i did notice that the bouncing to more pronounced during the fire cycle on the burner.

    the tank is located about 10' from the system via 1"BI pipe.

    any ideas why this is happening? i'm starting to think there's a broken valve.

  • #2
    Re: bouncing pressure gauge

    Steam or HW?
    If steam is there a pigtail?
    "It's a table saw, do you know where your fingers are?" Bob D. 2006


    • #3
      Re: bouncing pressure gauge

      Originally posted by Masterplumb
      It is absolutely normal to see fluxuation in a hot water system. As the water is heated the pressure will rise, and as the water cools the pressure will go back to static pressure.
      I agree there will be a pressure variance when the water is heated or cooled, assuming a HW system, but bouncing does not sound like the gradual rise and fall of the gauge one would expect from expansion caused by heating of the water.

      What kind of gauge are we talking here vince? is it a POS or something of decent quality?
      "It's a table saw, do you know where your fingers are?" Bob D. 2006


      • #4
        Re: bouncing pressure gauge

        If it were steam there wouldn't be an expansiontank. More likely the tank has been installed in the wrong location and the gauge is fluctuating as the circulator runs.


        • #5
          Re: bouncing pressure gauge

          i should have been a little more specific with the details.

          hw/glycol system, i guess it's not really a bounce but a constant osilation of the pressue. both boiler gauges are showing the same effect. the osilation is less pronounced when the burner shuts down, then it becomes a stable/constant pressure reading.

          single story construction, the system is not very big compared to what you guys have. it is however a "emergency measures" building in that if there is a catastrophic failure with the town's power generators, everybody in town moves into specific buildings that have independent power (genset). so you can see how very inportant this building is.

          fortunately for me, the building has been neglected since i last worked there (16yrs). i'm looking around all of the gov't assets and i'm seeing all these little drip cups and buckets. i was telling my girlfriend that it seems that's all the now retired plumber did was go to each building a empty the drip catchers.

          i say it's good for me because i work for a private contractor that has a "plumbing as and when required" contract with the gov't of Nunavut. chaaaching!!!

          my boss also has a "plumbing as and when required" for the petroleum products division of the GN. another chaaaching!!!

          you know, i have to say that i'm really happy i stumbled onto this forum. you guys really are a wealth of information.

          p.s. if anyone is interested insome Arctic Char, post me a private message.


          • #6
            Re: bouncing pressure gauge

            Almost seems like the weight of the water is oscillating back and forth in conjunction with the TXT once the circ kicks on.
            I wouldn't worry about it unless it were noisey.
            Last edited by DuckButter; 09-30-2008, 11:43 AM.