Munchkin boiler, Why did this work ?

Discussion in 'Boiler Forum' started by Tom Robinson, Mar 14, 2021.

  1. Tom Robinson

    Tom Robinson New Member

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    Mar 14, 2021
    Location:
    SAnta Cruz, California
    I'm replacing a 20 year old Munchkin boiler that reportedly functioned well. I appears that the primary circulation pump from day one was installed backwards. Also the air separator / expansion tank is low and on the primary loop as opposed to secondary loop ... most design drawings have the separator and expansion on secondary loop? Weil-McLain manual also states the pump MUST be on the return line so as to avoid cavitation while sucking from supply? Reverse pump and leave it alone ? It worked for 21 years.

    Munchkin Mess.jpg
     
  2. fitter30

    fitter30 Well-Known Member

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    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Try taking a pics of the side of the pumps thats where the arrow is for direction of flow. Normally grundfos pump label on motor top of label is discharge.
     
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  4. Tom Robinson

    Tom Robinson New Member

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    I made note on picture that suction was identified. I've been a domestic pump service tec for forty years, simple enough to see by casting shape alone where water is diverted into center of impeller.
    I just find it fascinating that the primary loop mixed the cold backwards and worked well enough to not create problems.. I've been a domestic c-16 pump contractor for 40 years so the friction / head / cavitation thing is no mystery. The thermal dynamics and air extraction that I don't routinely deal with.
     
    Last edited: Mar 14, 2021
  5. fitter30

    fitter30 Well-Known Member

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    Location:
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    Expansion tank on discharge of the pump would do anything for expansion the air separator wouldn't work to it design. Flow through the boiler backwards would cut the design temperature rise by half. Secondary loop tees backwards can't see how it heated unless theres more heat emitters than design. Read this article.
    https://www.pmmag.com/articles/93285-pumping-away-from-what
     
  6. Tom Robinson

    Tom Robinson New Member

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    thank you so much ... I love learning , excellent article !
     
  7. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Never seen a zone valve manifold made with that style of valve. Does it have a brand and model?
     
    Last edited: Mar 15, 2021
  8. Tom Robinson

    Tom Robinson New Member

    Joined:
    Mar 14, 2021
    Location:
    SAnta Cruz, California
    all Wirsbo
     

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