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Expansion on heat-pex piping.

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I was looking for some input from the group how they handle expansion on long runs of heat-pex tubing. This is for a snowmelt job that has a run approximately just under 100ft of 1 1/4" from the point of exit of the house to a 4 loop manifold. I ran the 1 1/4" heat-pex tubing in a 3' PVC conduit for the total run. Every time the snowmelt goes on the piping in the basement expands approximately 5"-6". I used expansion fittings for my connections. Just concerned over time they may leak because of the movement of back and forth. Spoke with Uponor and they told me not to be concerned, but we all have heard that before.
Mad Dog_2

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  • hot_rod
    hot_rod Member Posts: 22,467
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    No way to stop that expansion movement. As long as it is not stressing any fittings on either end, let it move. Sometimes an expansion loop is used, but they look funky.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Mad Dog_2Ironman
  • Allislandradiant
    Allislandradiant Member Posts: 36
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    I remember Uponor used to make a fitting to handle this, but no more. I am just concerned with Uponor expansion fittings putting stress on them.
    Mad Dog_2
  • hot_rod
    hot_rod Member Posts: 22,467
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    Yep, choices are to lock it solid, like encased in concrete :)
    Or leave room for it to safely move.
    A swing ell like you would use on threaded steel steam piping to allow movement may work, but 6" is a lot to accommodate
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Mad Dog_2
  • Allislandradiant
    Allislandradiant Member Posts: 36
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    Ok, thanks for your input. 
    Mad Dog_2
  • ethicalpaul
    ethicalpaul Member Posts: 5,792
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    Dumb question: when you "lock it solid like in concrete" what happens to the expansion then?

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
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  • Jamie Hall
    Jamie Hall Member Posts: 23,635
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    Dumb question: when you "lock it solid like in concrete" what happens to the expansion then?

    You wind up with a lot of compressive stress in the pipe -- which shouldn't be a problem -- which shows up as a very slight increase in wall thickness -- which also shouldn't be a problem.

    Now if there is a short section somewhere which isn't restrained... if the pipe decides to slide, which could happen, it will buckle and ruin your whole day.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Mad Dog_2mattmia2EdTheHeaterMan
  • hot_rod
    hot_rod Member Posts: 22,467
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    At the PPI website they show how to calculate an expansion arm. This may be cleaner than a U shape expansion loop?

    Enter the tube size, length and temperature change and it shows how to build the arm
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Ironman
    Ironman Member Posts: 7,397
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    This is one reason that we use PEX-AL-PEX when provision for expansion is not available. It only grows about 1” per 100’ @ 100* temperature rise. Very similar to copper. With PEX, it’s about 12 times that.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    Mad Dog_2
  • hot_rod
    hot_rod Member Posts: 22,467
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    Ironman said:
    This is one reason that we use PEX-AL-PEX when provision for expansion is not available. It only grows about 1” per 100’ @ 100* temperature rise. Very similar to copper. With PEX, it’s about 12 times that.
    Can you still find 1-1/4 PAP
    and fittings?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Allislandradiant
    Allislandradiant Member Posts: 36
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    Next time I will use fusion plastic pipe. That’s what we used inside. Nupi is the manufacturer. 
    Mad Dog_2