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Copper steam coil

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Kman638
Kman638 Member Posts: 1
in Strictly Steam
I have a trane air handler with a copper steam coil I am connecting to black pipe . The Engineer says I need dielectric union. I never installed before . Is this true ?

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  • Fred
    Fred Member Posts: 8,542
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    Brass

    You do need a dielectric union when transitioning from copper to iron pipe. Use a Brass union. Brass is a dielectric.
  • SWEI
    SWEI Member Posts: 7,356
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    Brass is a conductor

    but its position in the galvanic series reduces many of the problems created by direct connection of copper to iron http://en.wikipedia.org/wiki/Galvanic_corrosion 
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
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    Steel to Copper

    Many of our most experienced pros use copper for their wet return piping, and I've never seen any of them use dielectric unions, even for joints below the water line.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • ChrisJ
    ChrisJ Member Posts: 15,677
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    Dielectric union

    First, let me state I am a homeowner and do NOT have much experience with this.  On my steam system I did not use dielectric unions as I both could not find any and was told to avoid them by a friend of the family who has been a plumber for 40 years.

    He has owned his own plumbing business for 40 years and told me he has seen far more dielectric unions fail than just using a good heavy copper adapter.  Whether this is good advice or not I cannot say, but I have not had problems.



    I think the only one I noticed that tried to use something on his setup was Gerry Gill I think used a brass nipple to connect his header to his copper steam main.  If I missed others I'm sorry, it wasn't intentional.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
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    Electrolysis in plumbing

    I think a real study has been made (university of Wisconsin?) of the effects of mixing copper and iron on the same piping system. Their findings supported the advice against dielectric unions, and concluded that there was no problem.

    I suspect there could be a problem with copper pipe connected to galvanized pipe without a brass piece in between (think copper and copper battery electrodes).

    In our favorite heating systems, the water is almost so completely devoid of ions, that we should not worry.--NBC

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