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Expansion tank issues

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Comments

  • Big Ed_4
    Big Ed_4 Member Posts: 2,762
    Just Curious ......

    Take a look at what was piped and what is recommended . The tees are reversed . What has changed ? Would be the question ...
    I have enough experience to know , that I dont know it all
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Over thinking over pumping....

    Lets break it down to the basics.



    What influences water pressure. Pumps, and expansion.



    What is required in order to create thermal expansion? Heat.



    How much pressure can these circulators "generate" under ideal conditions? Is it enough to increase the pressure to the relief valves threshold? (I doubt it, even if they were in series)



    The expansion tank at B keeps the pressure stabile, but the tanks have been confirmed to be in good working order.



    If it were me, I'd eliminate fire from the equation first. If pressure remains stabile, then as others have said, you might be over fired, but something would have had to change DRASTICALLY to see that.



    Another possibility, the water ways of the aluminox boiler have become clogged, and the pump is creating significant back pressure, causing the relief valve to discharge. Possible but doubtful, because if it were clogged, the onboard controller would see th big delta and shut the burner down based on a no flow condition.



    And then, there is the real possibility that the T that the A expansion tank is tied into is rusted shut, hence no expansion acceptance ability.



    I have to give all of you credit for the thought you've given this, but I think we are over thinking the possibilities here. We are dealing with some fairly basic stuff here, and it hasn't always been a problem, so what changed?



    If worse comes to worse, leave the tank connected at the B point...



    Hang in there Ken, you will figure it out.



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • bob_46
    bob_46 Member Posts: 813
    Overthink

    Mark, I don't think we can over think this. Ironman came up with the way to correct the problem in the third post. I think it's worth trying to figure out WHY the tank doesn't work at A but does at B .
    bob
  • Big Ed_4
    Big Ed_4 Member Posts: 2,762
    Hmmmm

    Question ? Is this a new instal ? Has the problem always been ?
    I have enough experience to know , that I dont know it all
  • KCA_2
    KCA_2 Member Posts: 308
    Hard to say

    The gentleman has had two sidearms that have failed on him...  Both showed up by an increase in pressure in the heating system...  So now that they are fixed...  This has showed up..  System is about 6 months old..



       :-)  kCA
    :-) Ken
  • Big Ed_4
    Big Ed_4 Member Posts: 2,762
    Two ?

    Two you say in six months ? Condemned for a pressure problem ... I guess we can assumed this has been a problem since it has been installed ... Question again ...has the pressure problems started since the start of the heating season ?
    I have enough experience to know , that I dont know it all
  • Big Ed_4
    Big Ed_4 Member Posts: 2,762
    edited March 2012
    also

    where and how is the sidearm piped into the system in the first diagram ?
    I have enough experience to know , that I dont know it all
  • KCA_2
    KCA_2 Member Posts: 308
    The Sidearm

    is piped off the 1" supply manifold in the secondary...  On priority..



    Now it's a coil Weil McLain..  Before they were a tank in tank that someone installed..  Likely turned on the heating before the domestic was filled...



      :-)  KCA
    :-) Ken
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    tank

    It sounds to me like a bad tank - the system over pressures in just seconds after the burner starts - that means there isn't any room for expansion. I have had the diaphram get stuck to the top of the tank.
  • Paul48
    Paul48 Member Posts: 4,469
    Six

    zones pumping from a 1' supply manifold, pumping at the PONPC?
  • KCA_2
    KCA_2 Member Posts: 308
    Yeah...

    I thought of that and changed tanks..  Same thing..



      :-)  KCA
    :-) Ken
  • KCA_2
    KCA_2 Member Posts: 308
    ???

    It's pumping away...  Where do you see pumping at?  What am I missing...



      :-)  KCA
    :-) Ken
  • Paul48
    Paul48 Member Posts: 4,469
    In

    your original post approx. 2 weeks ago, you described this piping in detail, and I told you it was bass ackwards. In this posting,you drew the piping, and it is bass ackwards. You have hydraulic seperation between the primary and secondary loops, and you installed the expansion tank on the return of the secondary loop. "Pumping At"
  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
    I bet if you ran the circs whithout firing the boiler the very same thing would happen.

    Imagine the secondary circs running without the primary circ turned on. We know they will create a pressure rise across the system that will drop back to close to 18lbs by the time it crosses the closely spaced tees. All is well. Now turn on the primary circ. It grabs the 18.5lbs, lifts it up and scoots it throught the boiler around the primary loop and (BANG...) hits the supply tee were the pressure may not be more then 18.5lbs. So the primary circ then creates a signifigant pressure drop on it's suction side. The supply tee cannot see this though because if it could it would transfer it right on up to the expansion tank and reverse the flow. The return tee wll see this pressure drop though. It will grab it and transfer it back across the system. As soon as it hits the seconday circs they will do what circs do,create a pressure dfferential. Only this time since there already is a pressure drop at their discharge they will merely multiply the pressure drop and send it on back to the expansion tank and the PRV. The expansion tank doesn't have enough capacity and the PRV makes up the difference. As the PRV is adding water we know the pressure has to be rising somewhere. The most logical place.. the discharge of the primary circ.



    At least, this is how I see it in minds eye.
  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
    edited March 2012
    I bet if you ran the circs whithout firing the boiler the very same thing would happen.

    Imagine the secondary circs running without the primary circ turned on. We know they will create a pressure rise across the system that will drop back to close to 18lbs by the time it crosses the closely spaced tees. All is well. Now turn on the primary circ. It grabs the 18.5lbs, lifts it up and scoots it throught the boiler around the primary loop and (BANG...) hits the supply tee were the pressure may not be more then 18.5lbs. So the primary circ then creates a signifigant pressure drop on it's suction side. The supply tee cannot see this though because if it could it would transfer it right on up to the expansion tank and reverse the flow. The return tee wll see this pressure drop though. It will grab it and transfer it back across the system. As soon as it hits the seconday circs they will do what circs do,create a pressure dfferential. Only this time since there already is a pressure drop at their discharge they will merely multiply the pressure drop and send it on back to the expansion tank and the PRV. The expansion tank doesn't have enough capacity and the PRV makes up the difference. As the PRV is adding water we know the pressure has to be rising somewhere. The most logical place.. the discharge of the primary circ.



    At least, this is how I see it in minds eye.
  • KCA_2
    KCA_2 Member Posts: 308
    Expansion tank "A"

    is on the supply...  I put a tank in the return Ex tank "B"and it repaired the problem..



    Is that what you mean? 
    :-) Ken
  • KCA_2
    KCA_2 Member Posts: 308
    Yeah but

    the prv is turned off...  and this happens..
    :-) Ken
  • Paul48
    Paul48 Member Posts: 4,469
    I

    Don't know whether it is possible, but it wouldn't shock me if there was a thump from the flow control closing just before the valve discharged.
  • furnacefigher15
    furnacefigher15 Member Posts: 514
    Mark is right.

    This is simpler then we are making it.



    There is probably something wrong with the spirovent that is blocking the flow of water into the exp tank at point A.



    This system with it's undersized piping is probably experiencing higher then normal water velocity, and that velocity is polishing the cast aluminum in the boiler. Those particles have made there way into the spirovent and are mucking up the works.



    The spirovent makes for a good strainer too.
  • KCA_2
    KCA_2 Member Posts: 308
    Interesting that you said that

    The owner has $10 on it...



      Lol..  It might be...  I'm going to pull it apart tomorrow



    :-) KCA
    :-) Ken
  • icesailor
    icesailor Member Posts: 7,265
    Flow Control:

    If that is the case, manually open the flow control valve and the problem should stop.

    I installed a Munchkin once. I had my son pipe it. I gave him explicit instructions with a diagram on how to pipe it. He piped it as he understood the drawings. When I fired it off, because the piping was screwed up, the primary pump didn't come on for a heat call. It would run for a few minutes and a very few minutes, then the pressure would rise QUICKLY and the relief would blow. It was flashing in the boiler from lack of flow. There's a pressure switch but no flow switch.

    I still say, there's not proper flow through the boiler. If the supply loop gets hot quickly on the supply and return but not getting hot as fast into the secondary loop, there is a problem with the hydraulic separation

    Pumps piped in parallel can not raise pressure any higher than the highest rated pump in the system/circuit. Pumps piped in series can. That's how multistage pumps work. Each pump ads multiplication to the next pump by boosting the water from the first pump. But it can't have an outlet as it goes to the next pump. That's why Hydraulic Separation works.

    Turn the boiler down to make it run on the lowest fire possible. If it stops, the flow is either too slow, the boiler is over fired for the load or a combination of both.

    Whether you all want to believe it or not, someone I know where I work and does gas service work has gotten a lot of these complaints. He "solves" them by down rating or down-firing the boilers. Then, the problem goes away. He is absolutely convinced (right or wrong) that these teapot boilers are way over sized for their applications. I tend to agree.

    And I ask again and say again. You didn't install or design this problem. Have you done a heat loss on the building? Is the boiler (230,000 BTU's Gross) properly sized for the application? When only one zone is calling, is "Low Fire" low enough to keep the boiler from overheating?

    FWIW (nothing)
  • icesailor
    icesailor Member Posts: 7,265
    Pressures:

    Unscrew the #1 Extrol, add a 1/2" Bl Tee and bush it to put a pressure gauge. See if the pressure fluctuates at the Extrol when the "event" happens. Put one in place of the boiler darins around the system. You guys are just guessing. You need hard facts.

    GAUGE IT!!!
  • icesailor
    icesailor Member Posts: 7,265
    Steam:

    Then the only source of the pressure can only be from steam expansion. You can't do that with pumps in a closed heating system.
  • Paul48
    Paul48 Member Posts: 4,469
    I

    agree, and in all these posts there is a procedure to determine the cause of your problem. Get a pen and paper. Start at the top of the post, and add all the tests you have not done.Start with the simplest, which is most likely ices. Is the tank at position "A" seeing pressure change?
  • hot_rod
    hot_rod Member Posts: 22,024
    the relief valve

    has been blowing off since it was installed, possibly. If so the HX could be partially plugged fropm all that fresh fill water. How hard is the fill water?



    I'd agree that the connection to the tank from the purger is obstructed.



    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Paul48
    Paul48 Member Posts: 4,469
    It's

    worth eliminating it. Remember, he said it does it at 120 or 180 degress, it doesn't matter.Which tends to lead me away from normal thermal expansion in a properly operating system.The process of elimination will get to the root of the problem.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,762
    Agree

    Sure we are only guessing from behind a key board . First it's piped wrong from the start ... Seems it always been a problem ... I would also assume the boiler is over sized finding 99% are out there are , that makes sense too .... Most likely a combo of both ...



    If it were me I would repipe the boiler to factory spec first ... That is the first obvious problem which should be addressed , Any court of law would agree ... And yes drop down the heat output to its load . That is the beauty of these boilers ... After that blockage should be addressed if problem still exists



    Seems all the obvious , Feed valves , heat exchangers , domestic bypass , tank and tank pressure has been addressed ...



    Moving the tank from point A to B. ... What changes ? We all know pressures with circulators will change ... But why so dramatic to pop the safety ? The improper piping has to be an issue and that boiler also calls for that 0012 then add a high output boiler .



    Being a hands on guy myself. I need to touch and look to find the problem, that and the learning knowlage of how it should work . Then test to cut down the odds :) I am sure we are all doing the same ...
    I have enough experience to know , that I dont know it all
  • KCA_2
    KCA_2 Member Posts: 308
    edited March 2012
    OK... Here's what it was

    I pulled the top off the spirovent and..  Well take a look at the pics..



    Apparently, Spirotherm installs these in the spirovents but it looks like this one got installed upside-down...



    This would have been the last thing I would have expected...  But then there is a lesson in that for ya..



    By the way...  With all zones on the pressure buildup is about 2.5psi...



    Thanks everyone............



    :-)  KCA
    :-) Ken
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    I told you you'd find it....

    Good job.



    Hooda thunk....



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    Good Job

    So the water wasn't getting into the tank after all. When you are pulling your hair out it is usually something stupid. ( in this case the manufacturer)
  • Big Ed_4
    Big Ed_4 Member Posts: 2,762
    edited March 2012
    Funny

    The feed valve was connected to the same connection. There was no problems feeding the system ? You should have caught that
    I have enough experience to know , that I dont know it all
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    Big ED

    The feeder pushes water in - System water expansion pushes water out and into the tank.  The plastic insert was acting like a check valve blocking the bottom outlet to the exp. tank.
  • Gerry Alder
    Gerry Alder Member Posts: 25
    I throw out the plug

    The purpose of the plug inside the spirovent strainer is to slow the flow for when someone might do a fast fill like at startup it helps keep the vent from spitting water . Then later you run into problems like this one.
    ENJOY YOUR HEAT AND HOT WATER.
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