Exothermic Ground Rod

Discussion in 'Amateur Radio News' started by N5HZR, Sep 1, 2018.

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  1. WA7PRC

    WA7PRC Ham Member QRZ Page

    Several exothermic welds were used in my tower's buried ground connections:
    [​IMG][​IMG]
    click for bigly image(s)
     
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  2. WD0BCT

    WD0BCT Premium Subscriber QRZ Page

    That was exactly what I was referring to. It is pretty clear..."Connections depending on solder shall not be used." That was my point...and the topic of this thread is exothermic connections to ground rods. Please reread my post.

    Regarding compression fittings for use on ground connections...I recall when such fittings were first approved and Burndy and other suppliers demonstrated them to our electrical department. Most of the old timers didn't care for the compression fittings. I was a young buck and felt...if they are approved someone must have tested them!

    None of the engineering firms I worked for used soldered connections for a ground connection whether it was within a ground grid or connection of the grounded conductor to the electrode. The reason was that a soldered connection and high heat did not work to well for the soldered connection.

    Oh..and FYI MHZ my first introduction to the NEC was in 1960..but the approved revision was earlier than that. I was a freshman in a technical HS and little did I know I would be involved with that document for my entire professional career!
     
    Last edited: Sep 4, 2018
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  3. K8MHZ

    K8MHZ Ham Member QRZ Page

    I wasn't contesting you, just quoting some NEC stuff about where solder can and cannot be used.
     
  4. K8MHZ

    K8MHZ Ham Member QRZ Page

    This is what is used most of the time. No special tools required. I have never seen one 'blow up' or fail yet.



    [​IMG]
     
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  5. WD0BCT

    WD0BCT Premium Subscriber QRZ Page

    Sorry about the confusion...but you quoted me and I was not clear if you were disagreeing or agreeing.
     
  6. K8MHZ

    K8MHZ Ham Member QRZ Page

    I suppose I could have done a better job with that post. I just grabbed my oldest NEC and posted what I thought applied, I didn't mean to imply you were doing ground rods wrong.
     
  7. KV6O

    KV6O Ham Member QRZ Page

    I have. These are not allowed in R56 sites - the resistance can easily degrade over time as this is not a gas tight connection.
     
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  8. K8MHZ

    K8MHZ Ham Member QRZ Page

    I will be the first to admit that the NEC is a bare minimum set of standards. R56 is much stricter (and better) but I know of no where that has adopted it into law like the NEC. For those interested, here is a link to R56.

    https://sites.auburn.edu/admin/faci...ject Documents/1/Motorola_R56_2005_manual.pdf
     
  9. WB8LBZ

    WB8LBZ XML Subscriber QRZ Page

    Nice video. Even with the fail the recovery was good and that is all that matters.

    73, Larry WB8LBZ
    El Paso, TX
     
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  10. W2WDX

    W2WDX Subscriber QRZ Page

    Argh! NEC is not law. It's an accepted standard, and one adopted by the insurance underwriters in the US. That is the reason why the NEC is relevant to this discussion and in general. Insurance. R56 is a stricter standard, and is so due to the fact the NEC does not consider frequency and impedance, only the safety requirement for power systems at 60Hz. When considering RF it is not simply a matter of low resistance (which is fine for power systems); frequency and impedance is equally important. If impedance (not simple ohmic resistance) is high enough, such a ground connection will be "invisible" to some RF energy, making it useless for any RF grounding. Recent studies have also shown lightning can more often than not have a given percentage of its total energy present itself at frequencies as high as the low-end of VHF.

    Solder connections fail long before the wire. The issue is heat. The various connection methods mentioned are not the same. A copper wire will withstand much more heat than any solder connection, same for any brazing method. And anything other than perfect soldering/brazing means higher resistance (translating to faster heating) compared to exothermic connections. Also, brazing and soldering can have gas and liquid ingress or trapped, which will cause corrosion and higher resistance as a result over time. Neither soldering or brazing are like exothermic bonding, which uses heat to fuse two metal objects together by melting them with similar intervening joining metal(s) added to the process. Welding is similar, yet not quite the same. Brazing relies on the intervening metal for the bond. Soldering does not melt the joined metals at all and is not even a molecular bond of any kind. It's basically a conductive metal version of hot glue. Lightning will simply melt solder in micro-seconds and spit it out around your yard, long before the energy of the strike has dissipated.

    Mechanical connections can be used but only in specified connection points, and never on the common electrode part of the circuit.
     
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