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Hydraulics question

mferrer
mferrer Member Posts: 40
edited January 8 in THE MAIN WALL
Screenshot_20250107_154654_Word.jpg

I was in a situation and piped out a Chilled water return header feeding 4 coils. I mistakenly connected 2 out of the 4 returns directly opposite each other (as per the sketch). The other 2 coils are tied in separately further down on the vertical header.

Is this a problem? Will it create turbulence that will negatively effect the flow?

Thank you in advance for any comments!

Comments

  • ScottSecor
    ScottSecor Member Posts: 980

    I don't think it will be a problem with that large of a header.

    Ironman
  • hot_rod
    hot_rod Member Posts: 25,090

    Any idea of the flow rate on the branches, what size pipe?

    The 6" main may act as a hydraulic separator, should not be an issue.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mferrer
    mferrer Member Posts: 40

    There are a total of 4- 2" branches tied into the 6" header. Not sure of the flow rates. Each branch has a Hays balancing valve and a ball valve.

  • hot_rod
    hot_rod Member Posts: 25,090

    2” steel pipe, around 42 gpm at 4 feet per second velocity

    6”, around 360 gpm

    Are there checks at the coils?

    If that main is flowing that kind of gpm, I doubt the branches across from one another will cause flow interference, if that is the concern

    This wasn’t a primary secondary design? If so the S&R connections would be close coupled to the main

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 17,796

    360 gpm is pretty low for 6" you should be fine.

  • hot_rod
    hot_rod Member Posts: 25,090

    Larger size pipe over 2" is often sized by pressure drop. Engineers are comfortable with flows up to 7 fps in steel pipe, intermittent flows up to maybe 10 fps. velocity noise, erosion and pumping power are the considerations.

    This chart is a good quick reference.

    Screenshot 2025-01-08 at 10.10.21 AM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mferrer
    mferrer Member Posts: 40

    Thank you Hot Rod for the chart.

    The 2" Hays Valves have a tag on them labeled: 45 gpm. The system is a secondary Chilled water system originating at 3-large plate exchangers getting the Chilled water from a Chiller Plant. They feed several large floors, each with an AHU (6" S & R headers) that have 4 chw coils (2" outlets). No check valves on the coil branch piping.

    Thanks all- I am relieved to hear that there is a likelihood of problem-free operation. I will try to avoid Welding outlets across from each other in the future to play it safe.

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