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Phantom circulation in forced hot water

Bob_EngelhardtBob_Engelhardt Posts: 21Member
Last summer I replaced all the zone valves in a 5 zone hydronic system with circulators.  The zone valves had been a PITA and I thought I would do it "right" using dedicated circulators (1 per zone).  Now, I'm not so sure.



Anyhow, the problem is that I'm getting "phantom" circulation in zones that are not calling for heat, when a circulator runs in another zone that is calling.



I have attached a schematic of the whole system.  The piping is more or less proportional to the line lengths.  Which is why a couple of loops zig-zag - to represent their actual length better.  The triangles represent zone valves, each with a check valve.  A circle with an X in it is a balancing valve.  A plain line is 3/4" copper, a double line 1" and a triple line 1-1/4".  "M" is a monoflo tee.



The loops on the right are the 2 first floor zones and on the left are a basement zone and 2 second floor zones.  The phantom circulation is occurring in the basement and 2nd floor, especially the zone highlighted in red.  That happens when either (?) 1st floor circulators is running.



My diagnosis is that there is a venturi effect in the tee where the 2 main returns come together just before the boiler (at the red arrow).  There is about 8' of 1-1/4 pipe after they come together, until the boiler, if it makes a difference.



Do you think that's my problem?  If so, how do I fix it?  If not, then what?

Comments

  • Robert O'BrienRobert O'Brien Posts: 3,026Member
    Flow Valve

    I would install a flow valve between the boiler and the common return main
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  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    Like this?

    { Bell & Gossett Flow Control Valve)

    If so, why are there three ports?  I would think that you'd have an "in" and an "out".
  • Robert O'BrienRobert O'Brien Posts: 3,026Member
    Yes

    It's for either vertical or horizontal installation,plug the unused port
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  • TomTom Posts: 546Member
    Never seen a flow control

    Robert



    Excuse my ignorance, I have never seen that flow control before. How do they work?



    I can see the same as the OP that the 1st floor pumps are dragging the the water through the other zones how does the flow control work in stopping that? Not questioning if it will work, just how?



    Thanks
    Tom
    Montpelier Vt
  • ZmanZman Posts: 4,292Member
    Check Valve

    You need a check valve on each circulator. Right now when one zone calls, some water is being pulled backwards through the other zones.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    There is a check valve on each circulator

    Attached:

    " ... schematic of the whole system.  ... The triangles represent zone

    valves, each with a check valve. "
  • ZmanZman Posts: 4,292Member
    Circs?

    Bob,

    Did you mean the triangles represent zone circs with integral checks?

    I thought you got rid of the zone valves.

    Verifying the checks would be my first move. Is the heat moving past them? Which direction? A strap on dual temp gauge can be a useful tool.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    Kinda' like a check valve,

    Only with more "forward" resistance.  I.e., it takes more pressure to flow past the valve.  That pressure is adjustable.  The increased pressure stops phantom currents, which are driven by much smaller pressures than normal circulator pressure.



    Disclaimer: I didn't know about flow valves before this post & the above is what I learned searching The Wall.



    Bob
  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    Circs yes, zone valves no

    I did remove all the zone valves and replaced each with a circulator (previously there were 2 common circulators at the returns to the boiler - those were removed also).



    The check valves are not integral to the circulators.  Just one for each circ, immediately downstream of it.



    The strap on dual temp gauge sounds useful.  As a DYI'er, I have strapped on a digital cooking thermometer.



    Bob
  • TomTom Posts: 546Member
    Zman

    Its not a flow check problem the ghost flow is flowing from supply to return. When the 1st floor pump(s) start it pulls it through the other zones on the left side of diagram, so checks won't help this particular problem, but they are still needed.
    Tom
    Montpelier Vt
  • ZmanZman Posts: 4,292Member
    Ahh!

    Tom,

    I see where you are heading. I would think a good spring check would solve the problem you are describing as it would provide the necessary resistance.

    OP,

    What size are the circs?

    What type of checks are they.

    Pictures?

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ZmanZman Posts: 4,292Member
    Where?

    Where is you expansion tank? What type of boiler?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    More info

    The circulators are Taco 007-F5.  The check valves are swinging-door type (see pic).  The expansion tank is right above the boiler (on horizontal run immediately after 4' vertical out of boiler).  The boiler is a Weil-McLain CGs (sealed combustion), 125,000 BTU (?).



    Bob
  • ZmanZman Posts: 4,292Member
    OK

    The swing checks will stop the backflow I originally suspected.

    Tom is correct that it is not flowing backwards.

    The ghost you are seeing may be very slight.

    I think your piping looks reasonably good.

    I think spring checks would solve the problem. Swings just don't resist the flow enough.

    I'll bet if you swap the check valves it would solve it.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    Thanks - I'm going to use flow valves

    Right now there is one zone that is particularly bad with ghost circulation.  But I'll bet that ghosting is affecting all the zones somewhat.  So I'm going to replace all the check valves with flow valves.



    The one shown is $36 from PexSupply (http://tinyurl.com/n3uaq66).  That seems like a lot, compared to check valves, but whataya gonna do?



    Thanks for all the help,

    Bob
  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    edited August 2013
    Can I use this valve?

    It's a spring valve, but the description says "check valve".  What's the difference between this one and the Taco Flo-Chek in the previous post?  Is it just that the Taco can be manually opened to allow gravity circulation?



    I ask because this one is $10 and the Taco is $36



    Thanks,

    Bob
  • Jean-David BeyerJean-David Beyer Posts: 2,554Member
    What's the difference between this one and the Taco Flo-Chek

    An ordinary check valve allows flow in one direction and impedes flow in the other direction. But to prevent "gravity flow" you also need a check valve that does not allow flow in the forward direction if it is due only to temperature differences.



    A flow- check valve, such as the Taco one, has a weight in it that keeps the flow in the forward direction cut off unless there is a significant pressure in the forward direction. This prevents gravity flow but allows flow caused by running a pump or circulator.



    This link has an x-ray view of the Taco valve, so you can see how it works.



    https://www.taco-hvac.com/en/products/Zone%20and%20Flow%20Control%20Valves/track_file.html?file_to_download_id=15472
  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    The spring check valve

    OK.  Thanks - as much as I would dislike buying the $36 one if the $10 one would do, I dislike doing it wrong even more.



    Would it be correct to say that the spring check valve has a spring that is only there to close the valve when flow stops and is not strong enough to resist any pressure?



    Then, I'm lead to think that they could make a flow control valve from the spring check valve simply by using a stronger spring.  Which could be sold for about the same price (much less than the weighted one).  Just musing.



    Thanks,

    Bob
  • Jean-David BeyerJean-David Beyer Posts: 2,554Member
    Would it be correct to say that the spring check valve has a spring

    "Would it be correct to say that the spring check valve has a spring that

    is only there to close the valve when flow stops and is not strong

    enough to resist any pressure?"



    I do not think it would be correct to say that  but, on the other hand, I do not think it a good idea to rely on it either. A professional could give you a more definitive answer than I can. I can tell you my own experience.



    I have a boiler on the floor (in my garage) and two heating zones; one on a slab that is about five feet lower than the near boiler piping on the top of the boiler, and one upstairs, probably three or four feet above the near boiler piping.

    The system is piped primary-secondary. There is a 1 1/4 inch Taco FloCheck valve going up to the supply T. coming down from the return T is a plain Taco 007 circulator returning to the boiler. (I am leaving out unnecessary details). So when the boiler circulator runs, hot water is injected to the secondary loop. The secondary loop has two circulators (Taco 007-IFC) with spring check valves in them. The springs in them are pretty weak. The FloCheck valve in the boiler loop has no spring, but it has a substantial weight.



    So if the boiler is running (for the indirect) and not the heating circulators (they cannot run at the same time anyway) the FloCheck keeps the hot water from drifting up to the secondary.



    For my system, the light spring checks in the Taco 007-IFCs are enough. For one thing, since the lines to the slab drop about five feet to enter the slab, they do not get fravity flow anyway (heat trapped), and the spring checks keep one zone's circulator from sucking water from the other zone if its circulator is not running.



    So the only question is why I do not seem to get gravity flow in the upstairs zone. I think there are a few reasons.



    1.) The upstairs zone is only about three feet above, so there is not much weight difference to induce gravity flow.



    2.) The hottest I ever supply water up there is 135F and the delta-T up there is very low. Some on this site think that circulator is running too fast, and they may well be right, but that is what is in there until the circulator quits, at which point I will probably put in an ECM circulator of some kind.



    3.) There is over 64 feet of horizontal 1/2 inch copper tubing up there that probably does not encourage flow.
  • SWEISWEI Posts: 7,356Member
    There are a lot of different check valves out there

    using springs, weights, and more for various applications.  Sometimes you need a little more forward resistance, perhaps lower flow resistance after opening (on higher flow circuits) etc.



    The Flo-Chek (Taco) or Flo-Control (B&G) styles also include a lever which can be opened to allow for convection flow or flushing/cleaning.
  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    Follow up

    After a couple of months of distractions, I have installed the flow control valves that were recommended.  The system now works as it should, without phantom circulation! Thanks to all who helped with their replies.  This is a great forum.



    What's a "follow up" without a picture?  So, I've attached one of my (crowded) installation.  I think that it's pretty good for a recreational plumber.



    I did a couple of things contrary to recommendation, because it would have been somewhat-to-very inconvenient to do otherwise & because I couldn't see that it would be a problem.  Tell me if I was wrong.



    First, I connected the boiler feed into the main return, instead of at the expansion tank, which is where all the schematics show it.  I didn't see how it could make much difference, as very little feed should be needed.  What difference does it make?



    Second, the control valve installation schematic shows that it should be installed a minimum of 12" downstream of the circulator.  I installed 2 of them immediately downstream, not having much choice.  But I did wonder why it should be 12".



    Lastly, Taco says that their wet rotor circulators should be installed with the rotor axis horizontal.  One or two of mine are vertical.  Is this going to be a problem?



    Thanks again - you were really a lot of help.



    Bob
  • could've

    Could've just replace the zone valve with a better one and install a flo control valve on common return.
  • btw

    Btw, I looked at your boiler pix... sorry to say this.. another good boiler piped wrong..
  • ZmanZman Posts: 4,292Member
    RJB

    "another boiler piped wrong" seems to be your favorite line.

    If you wish to elaborate in an articulate and "helpful" way, that would be great. If you are just interested in cutting up other peoples work because you would have done it differently, why post?

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • i dont

    I don't do it different, I do it right as per boiler's manufactor and Dan's way... now, if you cansee what's wrong with this.. improper water feed location, improper pump and air scoop location ( in fact, this system doesn't needs a seprated air scoop) and what's else I'm missing from doing this kind of work for more than 30 years??
  • ZmanZman Posts: 4,292Member
    My point.....

    Exactly!
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    Tell me why

    I'm not challenging you - I really want to know.



    Boiler feed - what difference does it make?  With a sealed system the amount of feed water has to be insignificant wherever it enters the system.



    Why is the pump location "improper"?  Where should it be?



    Why is the air scoop location improper?  Where should it be?



    Why don't I need a scoop?  How would the air be released otherwise?



    Bob (the OP)
  • ZmanZman Posts: 4,292Member
    Thread

    Bob,

    I honestly cannot tell from your picture how your boiler is piped. An air scoop is a necessary part of most hydronic systems.

    This is a very good thread that explains what rjb thinks is wrong with your piping.

    http://www.heatinghelp.com/forum-thread/147640/pumping-away-PONPC

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RobGRobG Posts: 1,850Member
    rjb

    We are still waiting for your answer to Bob's questions? I'm with Zman, I can't see how the boiler is piped. I'm sure that to you "It looks like a furnace company installed the boiler". And please use spell check when you respond to Bob's questions. (too bad the site doesn't have grammar check as well).

    Rob



    Boiler feed - what difference does it make? With a sealed system the amount of feed water has to be insignificant wherever it enters the system.



    Why is the pump location "improper"? Where should it be?



    Why is the air scoop location improper? Where should it be?



    Why don't I need a scoop? How would the air be released otherwise?
  • EmpireEmpire Posts: 2,343Member
    Maybe it's....ME?

    I could not see any details in either the drawing or the picture.  I give you men credit in trying to rectify this obvious problem,..or not obvious... can't tell.  Pump away from the exp tank........save yourself tons. 



    P.S. rjb;  I think this sight has Spell cheek..............................................?lol



    Peace;



    Mike T.
  • Bob_EngelhardtBob_Engelhardt Posts: 21Member
    Some explanation

    I started this thread back in August because I had a phantom circulation problem.  That's been solved with The Wall's help and my "Followup" post was to announce that.  I am not looking for help now, as the system is working as I want it to.  I did post some questions in response to rjb's "good boiler piped wrong" reply, in the interest of perhaps learning something.



    He didn't respond, so I don't know what he thinks the problems are, specifically.  But I'll take a guess at it and elaborate.



    I am "pumping away" with all 5 circulators.  2 of them are within 2' of the expansion tank and while the others are further away, they are fed by 1-1/4" pipe, so the pressure drop will be minimal.



    The air scoop is directly above the expansion tank and not visible in the picture (hidden by 4" PVC air intake).  I can't see what's "improper" about that.  Maybe rjb thought that the flow valve next to the circulator was the air scoop.



    When someone tries to add weight to his argument by citing how long he has been doing something, I think of this: sometimes 30 years' work is just 1 years' experience 30 times.
This discussion has been closed.

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