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Correct Procedure for Filling a Diaphram Exp. Tank

Earthfire
Earthfire Member Posts: 543
in THE MAIN WALL
Could charging at cold temps and new cold tank from truck at 12 psi, increase pressure when heated to 180 degree operating temps? or maybe worn guage on either pressure check?

Comments

  • Louie O.
    Louie O. Member Posts: 12
    Diaphram Compression Tank

    Gentlemen,
    Is there any place thet I can obtain the proper way to air charge the air side of a compression tank. I've heard all sorts of procedures, where can I find the proper one???

    Thank,
    Louie O.
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,651
    \"proper\" method

    Hello: For domestic water, my understanding is you measure static pressure. With the tank disconnected or isolated from the plumbing, charge it to match the static pressure. Then hook it up. That is supposed to give you the maximum benefit of the volume of the tank. If you just isolate it; it needs to be done so that the water side of the tank is freely vented. Hope that helps.
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    In other words...

    ZERO p.s.i. on the water side when adjusting the air side of the tank upwards...and the air side should be adjusted to the calculated fill pressure, which for closed loop heating systems is roughly 1/2 PSI per foot system elevation above the boiler, PLUS 5 PSI.

    ME
  • Ted_4
    Ted_4 Member Posts: 92
    Too Much Pressure?

    Has anyone had experience with the diaphram side of the tank gaining pressure over time? I once checked a system that showed proper fill pressure when cold (12psi), but rose rapidly when the burner fired. I was sure the safety was going to pop, but when system pressure reached 20psi it abruptly stopped climbing. After some head scratching and curse words I measured the tank pressure after the system had cooled and had returned to 12psi, and -sure enough- it measured 20!! I released diaphram pressure until it measured 12, and everything went back to normal.
  • S Davis
    S Davis Member Posts: 491


    Your expansion tank is undersized for the system.
    Expansion tanks are sized based on total water volume of the system, if the expansion tank is undersized it will absorb all it can handle at wich point the system presure will start rising, when the system cools the presure drops to normal.

    S Davis
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    Sticking diaphragms...

    can be an issue with about any X tank out there. I've seen them ALL stick. Even the ones with talcum powder in them.

    Once it hits the "breakaway" pressure, things balance out, hence the 20 psi on the air side. BY lowering the pressure, you've just affected the tanks total acceptance capacity. The bladder is substantially distended. THe acceptance volume of the tank is seriously down. It is acceptible to see some raise in operaintg pressure when hot and under fire. It is not critical to remain perfectly stable. It IS important to stay below the relief valves thershold, by 10%. So that puts the maximum operating pressure to around 27 psi.

    If you're lifting the relief valve, there could be other problems, too many to list...

    I've had tanks where I had to let ALL the air out to "exercise" the bladder, then re-air it up to operating pressure and they've worked fine for a LONG time. Then theres those that last 30 minutes...
    It happens..

    ME
  • Ted_4
    Ted_4 Member Posts: 92


    Yes, I'm sure wierd things happen to these tanks all the time, but in this case the pressure on the diaphragm side WAS 20 lbs with the system at ZERO, as if the tank had been charged to that pressure. This was not the case since I had installed the tank myself, and it had performed normally for several years. Letting pressure out simply returned the tank to "normal", and it has been OK ever since, and operating within normal pressure limits. And the tank is definitely not undersized for the system.
  • kevin_5
    kevin_5 Member Posts: 308
    Maybe someone was messin' withit.

    It would sure explain the problem. And it's not that much of a stretch.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"
  • Louie O.
    Louie O. Member Posts: 12


    > It would sure explain the problem. And it's not

    > that much of a stretch.

    >

    > _A

    > HREF="http://www.heatinghelp.com/getListed.cfm?id=

    > 270&Step=30"_To Learn More About This

    > Professional, Click Here to Visit Their Ad in

    > "Find A Contractor"_/A_



    Is there an instructional site or liturature on what you men have been discussing?
This discussion has been closed.

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