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Primary Tee Direction with Low Loss Header Secondary

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Hello, I’m a long time lurker!

Question on Tee direction for primary secondary plumbing.

I would like to emulate this layout (borrowed from caleffi) however I’d like to confirm it is correct. I will be using only one boiler and would like two headers coming off the primary loop. In every other example it seems like primary loops always go through the “run” of the tees and the secondary is flows from the “bull” of the closely spaced tees. The diagram shows the opposite. Does the low loss header have to go through the run to decrease turbulence?



Comments

  • Snowmelt
    Snowmelt Member Posts: 1,418
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    I know what you’re talking about, if you go to the Weil McLain sights there done the same way as the same was as the diagram above, I even think navien does it this way also.
  • hot_rod
    hot_rod Member Posts: 22,396
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    It always been up to interpretation which loop is the primary. Is it the loop with the boilers within?

    The key to primary secondary is the properly installed closely spaced tees

    Although a buffer tank or separator/ low loss header also accomplish primary secondary function.

    It’s mostly about the “generous” size that allows two direction flow in that short section, header, or tank
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • colinbarry
    colinbarry Member Posts: 12
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    Is there a minimum distance rule (like 6 pipe lengths) between the closely spaced primary tees and the secondary branches? Thanks for your help
  • Ironman
    Ironman Member Posts: 7,388
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    Primary flow is from left to right in the diagram.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • hot_rod
    hot_rod Member Posts: 22,396
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    closer the better, a close nipple
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • colinbarry
    colinbarry Member Posts: 12
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    Thanks for your help, this website is a great resource.
  • JR_NH
    JR_NH Member Posts: 4
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    Hello,

    I've been researching this too and haven't been able to come to a definitive answer or rule of thumb. Let's say the boiler loop is always considered the primary. Is there a rule of thumb for which direction the tee's are assembled?

    Tee'ing out from the primary boiler loop or tee'ing in from the secondary heating loop? Does it depend on the flow rate for each loop?

    I primarily design radiant snowmelting systems. Most of the systems I design are based on a shared boiler system with a heat exchanger separating the snowmelt glycol loop. However, sometimes I am dealing with a dedicated boiler and want to make sure the P&ID diagrams I present clients will work, or that I at least solidly understand the concepts.

    I have been a long time lurker and finally registered. Thanks!
    CBRob
  • hot_rod
    hot_rod Member Posts: 22,396
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    Two different ways to pipe injection, direct or reverse
    This tekmar info may Help
    http://www.tekmarcontrols.com/images/_literature/365_d_06.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Tinman
    Tinman Member Posts: 2,808
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    The confusion is common. With customers, I refer to them as the boiler loop and the system loop without identifying which is primary and which is secondary.
    Steve Minnich
  • JR_NH
    JR_NH Member Posts: 4
    edited February 2020
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    Let me add two visual aids to my question. Maybe it has been answered and I am overthinking it!

    The attached pictures show two different tee piping arrangements. The snowmelt loop will have a higher flow rate than the boiler loop. Also, this is the only "secondary" loop/heating load.

    Which would be correct, A or B?

    Note: the drawings are not to scale so the spacing and pipe lengths aren't relative to proper sizing guidelines.



  • hot_rod
    hot_rod Member Posts: 22,396
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    What type of boiler if it is a non condensing type you need boiler return temperature protection

    If a mod con you have minimum flow requirements and adjust for any glycol mix for pump sizing
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • JR_NH
    JR_NH Member Posts: 4
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    99% of the time ModCon boilers. Which closely spaced tee orientation would be correct?
  • hot_rod
    hot_rod Member Posts: 22,396
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    Why not use a hydraulic separator? Air, dirt, magnetic and hydraulic in one https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_15_na.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    SuperTech
  • Gordy
    Gordy Member Posts: 9,546
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    ^and time saver.
  • colinbarry
    colinbarry Member Posts: 12
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    JR NH i was the original poster so I wanted to follow-up. I ended up piping mine like “A”, but i have a cast iron atmospheric boiler that is in the primary loop. If it were a modcon I would pipe it like “B” because the boiler loop is secondary to the primary loop.
  • hot_rod
    hot_rod Member Posts: 22,396
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    Drawing A is what I consider a primary loop with the boiler in that primary loop. Pipe size and circulator selection need to be correct to move the required gpm

    The secondary loop circulator pulls the required gpm from that primary loop.

    There are a handful of ways to pipe primary secondary piping. All methods have advantages and disadvantages
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • JR_NH
    JR_NH Member Posts: 4
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    I would prefer designing with a hydraulic separator as I think it's the simplest and most elegant solution. In cases where, for whatever reason, I would need to use closely spaced tee's I want to make sure I have sound design and logic.

    Thanks for the feedback.
  • Garfield
    Garfield Member Posts: 49
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    In Both A and B is the flow going the wrong direction? The closely spaced Tees are making the fluid flow the opposite way of the primary loop. Is this relevant? Thanks