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Hydronic system pressure increase issue need help with.

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Looking for some help identifying a problem I ran into yesterday that has my well... STUMPED!
Scenario:
- Assisted Living center with (5) 1992-1994 C.I. boilers and 1 Weil Mclain condensing boiler.
- 3 boilers have failed (leaking) in past 4 weeks.
- There had been an aluminum mod/con installed 2 weeks ago and was informed it had already failed a week later and a warranty replacement had been installed.
- System pressure increases from 15-25 psi throughout the day and maintenance person has been removing water from ceiling mounted compression tank multiple times daily so relief valves do not open up.
- The tank has a B @ G Airtol fitting connected to bottom of tank of which is connected to top of Roll Air eliminator.
- The make up water is totally isolated with (2) inline ball valves as well as RPZ inlet/outlet valves turned off.
- The inlet pressures to all (4) loop circulating pumps are in a positive pressure.
- System is being controlled by a Tekmar and SWT does not exceed 180 I am told.
- What in the world could cause something like this?

Thanks for any and all input!

Jim Hilpipre

Comments

  • Gordy
    Gordy Member Posts: 9,546
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    Are they making domestic hot water with indirects, or coils on the boilers?
  • Jamie Hall
    Jamie Hall Member Posts: 23,635
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    How is the air cushion in that expansion tank being maintained? Is it a diaphragm or bladder type tank, or is it a hyrdopneumatic? If it's the latter, are the air controls actually working? Is there any other air eliminator on the system?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gordy
    Gordy Member Posts: 9,546
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    I’m assuming a compression tank since there is an airtrol tank fitting piped off of a rolairtrol.
    SuperTech
  • Gordy
    Gordy Member Posts: 9,546
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    With the boiler failures, and IF there is DHW production using indirects, or coils. I’d suspect potable water entering the system some how. Since the fill valve for the system is off isolating that possible path.

    The question is if this was always a problem, or a recent development.
    SuperTech
  • JHilpipre
    JHilpipre Member Posts: 6
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    There are no indirect water coils or heat exchangers in this system.
    It only provides heat distribution through baseboard radiation, fan coils and reheats in VAV's.
  • Jamie Hall
    Jamie Hall Member Posts: 23,635
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    I'll go back to the compression tank. Check the air cushion in it. The airtrol may have failed...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gordy
    Gordy Member Posts: 9,546
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    Water logged tank is all that’s left I suppose.
  • SuperTech
    SuperTech Member Posts: 2,205
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    The only logical explanation for this would be issues with the compression tank. Maybe the failure of so many boilers is an indication that it's time to update the boiler piping to modern expansion tanks and air eliminators, preferably the microbubble resorber type. This should have been considered when replacing the first boiler.
  • JHilpipre
    JHilpipre Member Posts: 6
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    The compression tank has a sight glass and appears to be at 2/3rd level.
    I TOTALLY agree it is time to redo the system and am putting a proposal together but need
    to remedy pressure issues til end of heating season.
    The tough part is answering the question "why did it work fine until this year"? When I do not know that answer.
    On another note, I am having the water tested to see if any issues there causing failures.
  • Gordy
    Gordy Member Posts: 9,546
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    Okay one last thing. It’s filled to the correct level, but is it the right size? How many boilers were added from the original configuration with out changing the x tank size?
  • JUGHNE
    JUGHNE Member Posts: 11,102
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    Are the valves open to the sight glass? They are sometimes shut off if leaking.
    You mention reheat, is there any glycol involved?
  • SuperTech
    SuperTech Member Posts: 2,205
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    The level could appear correct but if a valve is shut off or the airtrol fitting is plugged up the compression tank won't do it's job of regulating system pressure.
  • JHilpipre
    JHilpipre Member Posts: 6
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    Gordy said:

    Okay one last thing. It’s filled to the correct level, but is it the right size? How many boilers were added from the original configuration with out changing the x tank size?

    Nothing new was added since 1994 until first boiler failure a couple weeks ago.
  • JHilpipre
    JHilpipre Member Posts: 6
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    JUGHNE said:

    Are the valves open to the sight glass? They are sometimes shut off if leaking.
    You mention reheat, is there any glycol involved?

    Yes, valves are open but there could be blockage in them causing gauge glass levels to be inaccurate. I did not drain tank, remove and inspect them that day.
    There is glycol involved.
  • pecmsg
    pecmsg Member Posts: 4,949
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    JHilpipre said:

    JUGHNE said:

    Are the valves open to the sight glass? They are sometimes shut off if leaking.
    You mention reheat, is there any glycol involved?


    There is glycol involved.
    Approved for Aluminum?
  • Grallert
    Grallert Member Posts: 669
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    Are the make up water valves closed? What kind of valves are they and is one of them failed? That's where I'd start.
    Miss Hall's School service mechanic, greenhouse manager,teacher and dog walker
  • Gordy
    Gordy Member Posts: 9,546
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    Even if the valve has failed, and is allowing water when system is at the prvs setting then it’s the prv.