O2 barrier pex with indoor Harmon boiler

Jmaskdc Posted By Jmaskdc, Oct 20, 2018 at 3:48 PM

  1. Jmaskdc

    Jmaskdc
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    Hi everyone. I'm new to the forum and hoping for some advice. I've just purchased a used Harmon indoor wood boiler. I have a lot of 1" O2 barrier pex that I was hoping to use for plumbing. Can I thread a nipple into the return and one at the output and attach the pex right at the boiler or is the firebox going to be too hot and melt the pex? And if I'm going to have to use black iron to get the pex attachment away from the boiler, how long does the BIP piece need to be?
     
  2. grader

    grader
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    where the line attaches to the boiler is just water jacket, so the heat is not an issue. if the lines are too close to the smoke pipe then that is a concern. also the pex when hot may sag so make sure it is supported as needed. for the cost, its easy to plumb it with pipe and maybe valves as well for isolation when doing mods, repairs, or pump changes etc.
     
  3. Jmaskdc

    Jmaskdc
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    Thanks. I'm taking your advice. Pipe is going to be pretty easy and will only run me about $50 in pipe and fittings.
     
  4. maple1

    maple1
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    I've seen it recommended here before to do all near-boiler piping in metal (copper or BI). I don't think it's firebox or stovepipe heat - maybe just possible effects of the pex always seeing the hottest water in the system at boiler exit all the time. Plus combination with pressure.

    Might also be dependant on your boiler & it's settings/operation.

    What are your pex specs?
     
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  5. Jmaskdc

    Jmaskdc
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    The pex is rated for 80psi at 200 degrees. That seems like it would be fine for 2 circulator pumps. Right?
     
  6. maple1

    maple1
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    I'm not so sure. Boilers can get above 200 at times. Even way over in an overheat situation - with pressure in the mix (raises the boiling point), even 220+ might be possible. Or a flash to steam event could cause a big pressure spike at a boiler output.
     
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  7. Jmaskdc

    Jmaskdc
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    I see your point. The only advantage to pex is that it would give me some flexibility when things don't like up perfectly. Would you suggest no pex at all? Or could I get away with some short sections to make things fit together easier?
     
  8. maple1

    maple1
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    I wouldn't use it until I got away from the boiler with near-boiler piping. It can be tough getting things to fit together. I used a combo of off the shelf black iron stuff, & copper. I could get things together with copper in tight spots by cutting & fitting, then soldering in place. There is a little give & take with that by for example not putting pipe quite all the way seated into a fitting. BI, I was at the mercy of where fittings ended up after tightening. Using close or short nipples in between fittings, vs. say one fitting right into another, gives another set of threads to turn on and better ability to get things lined up. I am no pro, just a DIYer - a pro with a pipe threading machine and experience could likely do it all up no problem and have it look good to boot.

    My system has manifolds going to zones - if I wanted to use pex, I wouldn't do it until I got to the (supply) manifold. Which is also past the boiler bypass piping. The return side, it would maybe be safer to use pex right up to the boiler, or bypass piping. But there is still always the question that if something goes wonky or malfunctions, stuff could get hot were it isn't supposed to get that hot. I have seen pics of guys having their pex split, on OWB near boiler stuff. Might have been an odd occurance - but have seen it. Likely excessive heat over time, since they shouldn't build pressure.
     
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  9. heaterman

    heaterman
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    Metal should always be used for the first piping off a wood or pellet boiler. Period.
    We always pipe up at least the first 5-6' in steel, if not the whole main manifold, then use pex if need for the takeoffs from that.
    With any solid fuel equipment you have to bear in mind that the fire does not simply turn off when the control says, "no more heat".
    There's almost always an overshoot and in cases where something fails like a circ or control you can get well past the point of no return on pex very quickly. It's tough stuff but once you get past 200* the pressure holding ability drops like a pregnant elephant off the Empire State building.

    Use steel or copper and be safe, which of course does not always equal cheap or easy.
     
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