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dan's 'pumping away' book

phew! fortunately, i tested it before taking it in. and i'd'a had a hard time explaining a failure when i'm trying to convince workmates of the better science behind pumping away

yeah, i wondered about the gauges vs small measurments, and i'll have to wait until tomorrow to get a mag and or more sensitive gauges

but ya know, when i made a 'leak' in the system by opening an 'air bleeder' valve, i did seem to see a diff just before both gauges went to 0. and what i'm hoping to see is a vacuum at the critical point, in order to prove that the system, when improperly plumbed, could take in air at any leak

thanks

Comments

  • where did i go wrong?

    for show 'n tell, i made a pvc model of dan's drawings on pages 11 & 12; pump, gauges, comp tank etc, but when i try to demonstrate the pressure diff by moving the tank in relation to the pump, the pressures aren't cumulative nor subtractive

    maybe it's a pump and not a circ; ie, it's a jabsco 12460-0011, 10'head, 1.7gal/min
  • It`s the pump,

    in conjunction with your loop piping. At that low a flow rate, the gauges will have a tough time discerning the differences in pressure, but it`s there!
    Try installing an artificial throttling device[BV], ahead of the pumps discharge and pressure gauge, then adjust-it[running] to 16PSI with a 12 PSI static fill, and remove the handle,,,then move your tank to either side[of the pump of course], and see the difference.
    Or just get another circulator LOL!!
    Don`t you just hate demos when they make you look bad?

    Dave
  • scrook_2scrook_2 Posts: 610Member


    You using a differential pressure gauge in addition to a regular gauge or just two regular gauges? Small differentials are hard to measure accurately when everything is at a higher static pressure (say 12 psi static and 3 psi diff (~7 ft). Can you rig a Magnihelic gauge w/o filling it w/ water?

    Is the tank pressure at or just below the static system pressure?

    Are you operating close to the high head end of the circ's head-flow curve?

    "Pump", "Circulator" -- same thing
  • Barking up the wrong pipe...

    Under your scenario, IF you had an automatic air vent at the top of the system, and IF you had a marginal fill pressure, and IF your system was tall enough, and IF it was a high pressure drop system it IS possible for your pump to create a slight negative pressure at the very TOP of the system, and then the automatic air vent COULD become a vacuum breaker, therby introducing air into the system.

    Remember that pumps in series ADD their pressure differential together. So in your case, you have a 30 footer, PLUS whatever other pumps you have in the circuit (because the big pump is essentially in series with the other pumps...) they could SUBTRACT their pressure differential from the static fill of the system.

    Why the heck is the big pump on the return in the first place? Is it really necessary for proper fluid movement or did someone add it trying to overcome another problem. Funny how things like that happen...

    No, the pump can't push back water into the expansion tank. The tank is considered the PONPC (point of no pressure change). And as the name implies, the pump can not influence the pressue at that point.

    Generally speaking, the loss of air from your compression tank is usually associated with the misapplication of automatic air vents. Either get rid of the auto vents so the system air is redirected and stored in the compression tank, or install a diaphragmatic expansion tank and leave the air vents in place. Also, try running the system without the helper pump and see what happens. Unless theres a bypass somewhere, that pump could have a tendency to dead head, and dead heading leads to other problems.

    If that pump is absolutely necessary, move the PONPC connection to its inlet and it will then ADD its pressure differential to the systems static fill pressure.

    I used to have a series of articles on expansion tanks available on line, but the new owners of the magazine I write for have completely changed their web site and it no longer comes up. Send me your email address and I will get you the raw articles in WORD format.

    One more important note, if when servicing the old style expansion/cushion tank, if it is not COMPLETELY drained, and allowed to equalize its pressure to the atmosphere, you are wasting your time. This is one of the most misunderstood parts of servicing the tank. Do it right and completely, or don't bother messing with it. The key to not wasting 3 hours waiting for the tank to completely drain itself due to the GLUG factor is the ability to allow air into the tank as the tank is draining. I serviced a 50 gallon tank the other day in 30 minutes FLAT. And it was COMPLETELY waterlogged. The building manager said "No ones ever done that before in the 25 years I've been here... They just let some water out and call it good" To which I replied, I hope you haven't been paying them for that service...

    ME
  • please send me the article

    [email protected]

    your other questions/points i'll get to when i get back home

    thanks
  • yeah, i know what you mean

    a lotta IFs

    why the big pump? i'm really not sure because i don't have the option to talk to the person/s that did the original install. system/boiler circulation? and here's the kicker; it's 3ph, and it most likely has been running backward as indicated by the 'rooster tails' that were generated from the leaking seal

    "move the PONPC connection to its inlet"; yeah, that's what i keep tellin em, but they have more yrs in the field than i do, therefore.........

    get rid of the auto vents? yeah, that's what i keep tellin em.............

    yep, a workmate drained the tank after the 1st logged episode, but the only details that i know for sure is that THE home office svc mgr showed up and tried to tell the workmate how to do it properly; plenty of tension, so for now, i don't ask workmate about it

    yep, it's VERY frustrating, and i want to kick them all out of the way and have my way with doing it properly. and i will in the end because i'm determined to break their habit and blind them with science. what's dan say about the power of habit?

    to be continued...........
  • Article links...

    THanks to David Goldman for rediscovering them for me. Thanks David, I owe you...

    http://contractormag.com/hydronics/cm_column_45/index.html

    http://contractormag.com/hydronics/cm_column_60/index.html

    http://contractormag.com/hydronics/cm_column_75/index.html

    Enjoy, and pay it forward...

    ME
  • Bob SersenBob Sersen Posts: 4Member


    Well written Mark.If those who use an old style compression tank would spring for the tank fitting by B&G, there would never be a problem draining a tank.
  • actually,

    the tank has an b&g atf-16
  • joe_94joe_94 Posts: 39Member


    Would you please remind me HOW to use the B&G fittings on my old style expansion tank?
    I have an Airtrol into the tank on the line up from the in-line air separator,
    and a Drain-O-Tank in the middle of the tank.

    Each has a slotted screw head in the center. Each has a tube rising about 2/3's up into the tank's diameter.The Drain-O-tank has a hose bib.

    I reckon there is five year's worth of siphoned off
    air up there. I have a slightly weeping pipe leak so there would be some air coming into the sytem .

    Note, our set-up does not have automatic fill.
    Do I shut off valve between expansion tank and IAS/boiler piping and bleed out air till water spits out. Or leave that valve to system open as I bleed off air. The directions are not clear.Do I even need to do it?
    Thanks, joe
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