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A Question About Monoflow & Venturi Tees- Scoop vs. Orifice

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PGB1
PGB1 Member Posts: 81
edited February 2023 in THE MAIN WALL
I know there are many questions about monoflow and venturi tees, not only here but on the whole wide web. A curiosity came to mind, and I'm asking here for what you all think.

In school and on my apprenticeship, I was taught:
Monoflow Tees are the ones with the ramp inside. A "Scoop". These Scoop tees are called "monoflow".

I was taught that orifice tees (also called "venturi") are the ones that have the restriction inside that looks like a cone.

I was also taught that one does not have to use two scoop style for radiation-below-the-main. (It works in my house on one unit.) Venturi (orifice)requires two when below.

Also taught: Monoflow (scoop) spacing is not critical since there is a ramp to force water up. (Orifice, of course, needs pressure drop- whether by spacing or a balancing valve.)
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In my house, the original "before I was born" hydronic zone has monoflow style tees, not venturi. (We have the ones with the scoops inside.) One's so old, it's an OS brand. Every one of them is on the supply side to the radiator. Each has the arrow pointing away from the scoop's entrance. (Direction of main's flow)

Years ago, I asked someone at B&G engineering. The guy said scoop tee should be on the supply side. (And he confirmed venturi on return)
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But...
Each article I've read lately says monoflow (scoop) AND orifice (venturi) MUST go on the return side. Could the authors be accidentally lumping the two products together? Or, are there new rules?
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My Take:
Having a venturi (orifice type) tee on the return side would clearly provide smoother and more peaceful flow, probably with more volume. On the supply side, it seems air purging would be more difficult. (Been there, fought that...)

With a scoop (monoflow) tee, it seems having the scoop (ramp) aiming at the water flow would force part of the water up the ramp & into the radiation unit. Some goes up the ramp & some goes past.
On return side, the ramp would act like the orificedoes in a venturi tee- create a traffic jam, forcing water to detour through the radiation.
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Am I wrong, or are scoop (monoflow) tees ambidextrous? If they still exist, is there a standard practice for scoop (monoflow) tee location?

Thanks for bringing this out-of-date brain up to date!
Paul

Comments

  • hot_rod
    hot_rod Member Posts: 22,476
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    Lots of different terminology being thrown around.
    But the function is the same, add resistance to cause flow to go through the heat emitter.
    A true "designed" diverter tee system is a bit involved, pressure drop, temperature drop math.

    Here are some basics.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,568
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  • hot_rod
    hot_rod Member Posts: 22,476
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    And and the concept of closely spaced tees starts to seep into the conversation
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,839
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    You have to space the tees out usually the width of the radiator or baseboard will do. Mono or venturi tees were put on the return as standard practice, but they can be put on the supply instead of the return ....you have to reverse the tee to do it.

    Below the main they used to say use two tees 1 supply and one return but one tee can work ....It's all about the resistance of the circuit. Two tees were used because it is more difficult to drive hot water down than up
  • hot_rod
    hot_rod Member Posts: 22,476
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    Know also that the reduction inside the diverter tee will cost you a bit of pressure drop
    25’ EL for an 1-1/4” monoflo

    The 3/4” size is a substantial hit at 70’

    So some hydraulic baggage in one pipe systems to account for.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • PGB1
    PGB1 Member Posts: 81
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    Thank You all for taking time to reply and for the very helpful information.
    The Q & A that Dan Holohan linked has been a favorite reference for me for a while. It's very well written.

    The pressure drop Hot-Rod mentioined for diverter tees was startling at 3/4" What a penalty!

    Thanks for the Caleffi pages, Hot-Rod. They're good articles. (I've used Caleffi products in industrial at work and don't think I've ever had to return one. Lots of innovative items, too.)

    It was mentioned "lot of terminology being thrown around". My Fault.
    I confused stuff even more by forgetting to attach my drawing of which type goes with which of my words.

    Terminology was part of my question. I read articles and articles and books- Each one seems to get "scoop" and "orifice" tees lumped together.

    To me:
    Scoop or Monoflow is the one with the ramp. Venturi or Orifice is the one with the backwards reducing coupling inside.

    Scoop: Supply or Return. On supply, it "scoops" water into the branch. On return, the ramp creates a traffic jam, causing water to detour. (A helpful verbal illustration used in Dan Holohan's Q & A).

    Venturi: Return Only It creates the aforementioned traffic jam


    Hopefully the drawing will let you guys know which one my mind calls which. (Hopefully....)
  • hot_rod
    hot_rod Member Posts: 22,476
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    Monoflo is a B&G trademark name, without the "w". The red ring is another indicator. Pretty sure this brand has the cone shape reduction inside?

    The little curve or ramp inside others is also just adding resistance, with a different shape instead of an orifice, cone, funnel, etc. It's not really scooping in my mind, just blocking the main highway.

    It's really more about understanding what they are doing, not whats inside. Diverting a portion of the flow.

    Probably diverter tee would be the best general term for the various types.


    I've know installers to drop a nickel inside a 3/4" tee with a 1/4" hole drilled through. A "plugged nickel" tee.

    This hydronic light fixture I built has a bunch of drilled nickels, at every branch.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • PGB1
    PGB1 Member Posts: 81
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    The light fixture you built, Hot-Rod, is cool looking. Very creative.

    "Diverter Tee" sounds good to me
    I suppose the word Monoflo(w) is like saying Kleenex. A trade name that became generic.
    The Red Ring's I've used had the cone. The one's I've seen marked Monoflo have the ramp. Who knows if that's universal.

    You mentioned nickels in tees. On jobs, I've encountered some 3/4 x 3/4 x 1/2 copper tees that had 1/2 x 3/8 copper reducing couplings tack-brazed inside. Since they were in various facilities, I wonder if they were factory made somewhere.