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pex loop of steam boiler

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STEAM DOCTOR
STEAM DOCTOR Member Posts: 1,974
in THE MAIN WALL
Good eve. I was someones house(social visit) and he invited me down to the basement to see his under construction basement. First thing I noticed was the plan for heating the basement. Baseboard fed by pex feeding off a steam boiler!! Took closer look at pex. In very plain English it says not for heating. Obviously they will have to take it out. Do they make pex that can handle the high temps of steam hot water(212 at 0 psi) ? thanks

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  • Ironman
    Ironman Member Posts: 7,376
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    No Pex on Steam

    You can use copper to run a baseboard loop off of steam boiler if it's properly connected below the water line on both supply and return. A non-ferrous circ. and an aquastat is required.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Rich_L
    Rich_L Member Posts: 81
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    Not so sure?

    I've never done it and don't believe I'd recommend it but I'm not so sure you couldn't? This is off of Uponor's web site for their Aquapex brand:
    • 200°F at 80 psi
    • 180°F at 100 psi
    • 120°F at 130 psi (1/2" Wirsbo AQUAPEX tubing only)
    • 73.4°F at 160 psi




    • I'm sure there's an upper temperature limit but I don't see that right off.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
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    I've done it before, but probably wouldn't do it again.

    Too many things can go wrong in a heart beat. The system was designed by a former sales person, and installed by our crew. I was late to the party, or I would probably have suggested doing it in copper. When the steam boiler is running on steam, the condensate is extremely hot, and the PEX is like a rubber garden hose as it pertains to flexibility. Pretty scary when you consider what COULD happen if the tube were to breach. I don't like operating things at or near its limitations.



    As it pertains to the PEX not being certified for heating, I'd be worried about that. Probably non oxygen barrier tubing. The only way I'd consider using PEX off of a steam boiler would be if I had a heat exchanger between the boiler and the load whereby I could control the temperature of discharge, and if you're going to go to that expense, why not just set a separate high efficiency heat source, and have it do your DHW at the same time.



    ME

    There was an error rendering this rich post.

  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,974
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    Oxygen barrier

    How much of an issue is the oxygen barrier on an open steam system? Steam systems are open systems (via the air vents) and should have an endless flow of oxygen. Please correct me if I am wrong!! Thanks again to all for sharing your valuable knowledge!
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
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    You'e right...

    But I still would recommend a barrier type of tube in anything but a potable hot water heating system.



    ME

    There was an error rendering this rich post.

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