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Straight pipe before pump

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CBRob
CBRob Member Posts: 273
Saw an install that speced so many inches of straight pipe before and after the circ pumps.

I suppose this helps with flows and turbulence.
Do you try to keep this in your own install all the time?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,635
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    It is certainly advisable; inlet more so than outlet. I'd try to hold 10 diameters if possible.

    The problem -- particularly on the inlet side -- is that if there is a bend closer to the inlet, you can get unbalanced pressure on the rotor. If the inlet pressure is low -- getting down to the required net positive suction head -- this can cause cavitation. Even with adequate pressure, however, it can cause unbalanced forces on the seals and bearings. Either one can lead to shortened pump life.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    CBRob
  • Gordy
    Gordy Member Posts: 9,546
    edited November 2019
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    https://us.v-cdn.net/5021738/uploads/FileUpload/46/798d393e695b44af28da4f345362a2.jpg

    Not always possible depending on space provided in the mechanical room.
    CBRobSolid_Fuel_Man
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    Keep in mind also some of those pre-made panels with package boilers are tight. So tight I can't imagine ever making a plumbing repair.
    So try for the right dimension if you can get it.
    I can tell you on my own house, there just wasn't enough room with 6 zones/circs.

    There was an error rendering this rich post.

    Canucker
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    It's interesting to note that in pretty much all wet rotor circulators (choose your color) the inlet (suction) is a 90 degree bend right into the impeller.

    We all know this isnt true on base mounted pumps of any real horsepower. The inlet is a straight line to the center of the impeller.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
    Gordy
  • Jamie Hall
    Jamie Hall Member Posts: 23,635
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    It's interesting to note that in pretty much all wet rotor circulators (choose your color) the inlet (suction) is a 90 degree bend right into the impeller.



    We all know this isnt true on base mounted pumps of any real horsepower. The inlet is a straight line to the center of the impeller.

    True. But in your wet rotor circulators it isn't just a simple elbow -- some poor soul spent hours on a model table (or computation fluid dynamics program) getting the geometry of the bend right to get an even pressure distribution at the flow rate of best efficiency. It's amazing what small tweaks to the geometry of the flow can do...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Solid_Fuel_ManCBRob
  • Gordy
    Gordy Member Posts: 9,546
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    I think in residential sized circulators it’s splitting hairs. Look no farther than onboard circulators in mod/cons.........
    CBRobCanuckerSolid_Fuel_Man