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H B smith tankless coil

Hello what size are the studs or threded rods or bolts as you would say coming out of the boiler and what size nuts are they attach to threaded stud


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    Measure them. Can I assume you need to replace your thankless coil?

    There was an error rendering this rich post.

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,060
    edited December 2020
    I believe the thread size is 3/8" course but I could be mistaken. the smallest I have seen is 5/16" course. The nuts are wider than the standard hardware store version so, if you are replacing them you will want to add a flat washer.

    Some manufacturers use a threaded hole in the boiler and bolts, and I remember ThermoDynamics used a flange on the boiler with nuts and bolts so when you broke off the nut it was easy to replace without drilling and tapping the boiler casting.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    EBEBRATT-Ed Member Posts: 15,614
    I have also seen the somewhat rare 7/16" which I still mistake for 3/8 most of the time.

    3/8" is most common.

    Do yourself a favor and use anti seize on the threads if you get it apart