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Is this OK? Service bypass for radiators

JohnnyCB
JohnnyCB Member Posts: 23
Hi All,



I am remodelling a room in my house that has baseboard radiators. I

have removed them, and am replacing them with wall-mounted radiators of

what I think is the right BTU rating (more on that later) but what I am

wondering is this:



The system is piped primary/secondary. The secondary consists of three

zones, all in their own monoflow loop. Zone one is the off-boiler water

heater. Zone two is the upstairs zone, zone three is the zone I am

replacing some of the baseboard rads in.



This zone three was all monoflow baseboard - just one pipe from the circulator through all the baseboard in one loop.



The part of the baseboard I am replacing with rads I will (correct me if

wrong) pipe with a monoflow tee branching off into the rad, the return

comes back to a regular tee. In other words, a bog-standard parallel

loop with monoflow tee on the input.



What I am wondering about is this: If I were to put full-port ball

valves on the send and return portions after the tees, and *another*

parallel pipe between them with a ball valve in the middle, I would then

have a service loop, right? In other words, with the send/return

valves open and the loop valve closed, the rad functions as normal, but

with the send/return closed and the loop open, it would bypass the

radiator with a pipe to return full flow from the monoflow tee input.



Make sense? Or is there a reason that this would interfere with proper flow somehow?



Thanks in advance,



-John

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Comments

  • Zman
    Zman Member Posts: 6,983
    Do you have?

    Do you have an existing monoflow setup or a typical north american baseboard in series? Do you have monoflow tees now?

    I think you are trying to end up with wall mounted radiators with trv's. If you have monoflow now it should be fairly simple. If not you will need either monoflow tees or a trv with bipass setup.There was a long post on this recently regarding trvs and baseboard heaters.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • JohnnyCB
    JohnnyCB Member Posts: 23
    Yep! That's where I'm at.

    Yes, I currently have series baseboard.  And also correct, I'm trying to end up with rads with TRVs.



    I was thinking of adding the monoflow tees to the series pipe (one on "feed" side, regular tee on return) and adding a wall-mounted rad with TRV on the resulting "loop".  I was also thinking that while I was at it, I could add a bypass with valves in case I needed to service a radiator without affecting the rest of the rads in that zone.



    -John
  • JohnnyCB
    JohnnyCB Member Posts: 23
    Diagram

    Sorry for the bad art, but maybe this would help explain.  Flow from left to right.
  • Zman
    Zman Member Posts: 6,983
    Caleffi

    I believe caleffi has a new product that does all this with one valve.It even has the correct spacing to bolt onto the radiator.The rep at ARH told me about it, I did not see it on their web site.

    If you go the monoflow route, you should get Dan's "classic hydronics" book. He does a great job of explaining monoflows.

    Right of the bat, I would say there is no reason for the bipass loop. You should also put the Tee on the return side. You also need to pay attention to the cv rating on the trv. The spacing of the tees is also critical. Read the book and it should make perfect sense.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Zman
    Zman Member Posts: 6,983
    You don't by chance..

    Do you have the ability to run 1/2 pex from a manifold to each radiator?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • JohnnyCB
    JohnnyCB Member Posts: 23
    OK

    Thanks - I'll check that book out.



    That bypass loop was just a thought - it would allow me to bypass the radiator if, for instance, it started leaking or whatever, and would allow me to take it out and replace it  - but would still have a loop that flows correctly because there was a monoflow feeding it, thus needing a full-flow return.  In other words, leaving the rest of the zone operational while it was repaired.  Not necessary of course, just thought it might help in a pinch.



    I'm puzzled as to why the monoflow tee would go on the return side though.  In this configuration, wouldn't it divert most of the flow into the rad, making a standard tee OK on the return?  I guess I'll have to check out that book!



    Thanks,



    -John
  • JohnnyCB
    JohnnyCB Member Posts: 23
    Sure

    I'm not exactly averse to re-piping that whole section, so sure - I could do that.  I don't have any PEX tools, but I was thinking of getting them.



    What do you have in mind?



    -John
  • JohnnyCB
    JohnnyCB Member Posts: 23
    Oh I see

    I just read this site: http://www.comfort-calc.net/monoflo_system.html



    ...regarding the venturi/monoflow tees.  So, I gather what you are explaining above is that I would put one on the supply side as shown AND on the return side, as per the site's suggestion for "higher resistance radiators", correct?



    If so, that makes sense.  I can also understand the example of just using one on the return side for the venturi effect.



    -John
  • Zman
    Zman Member Posts: 6,983
    One tee or two

    I would think you could design your system with one tee. It just depends on the pressure drop through your trv and radiator and the type of system circ ect.. They are all a little different.

    If you have the ability to "home run" each radiator, I absolutely would. The loops would all come back to a manifold either in the boiler room or somewhere else (connected to your existing 3/4 line). This would give you perfect flow to all you radiators without the potential headache of installing and purging the monoflow.

    Pex tools are not very expensive

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • JohnnyCB
    JohnnyCB Member Posts: 23
    How about...

    Thanks Carl.



    So, if I understand you correctly, I can leave the upstairs zone and HW heater alone, and just manifold the third zone (downstairs), and it would look like my bad attached drawing.  (One circ per zone on the return side currently).



    Right?



    -John
  • SWEI
    SWEI Member Posts: 7,356
    circs

    Should be "pumping away" from the expansion tank, which almost always puts them on the supply side of distribution loops.
  • JohnnyCB
    JohnnyCB Member Posts: 23
    I've heard that

    ...from several people.  The way this was set up is that the circs are on the return "pulling" through, the expansion tank is where you'd expect it on the supply side.



    I might just re-pipe most of this system - the last boiler replacement was done by someone too lazy to change the original 1930 setup much...



    -John
  • Zman
    Zman Member Posts: 6,983
    That is..

    That is what I was thinking.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • JohnnyCB
    JohnnyCB Member Posts: 23
    Thanks!

    Sorry to resurrect an old thread, but I just wanted to say thanks - everything worked out PERFECTLY.



    I got rid of all the monoflows, made manifolds for zone one out of 3/4" copper and full-port ball valves, (in the same way shown), and I dare say, it works much better than it ever did before.  Heck, it even seemed easier to purge!



    Also, thanks for the suggestion on Dan's book.  I got a copy, and it was a wealth of practical knowledge.



    -John
This discussion has been closed.