Can't bond ham shack ground to service entry ground

Discussion in 'General Technical Questions and Answers' started by AE0AQ, Mar 6, 2018.

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  1. K8MHZ

    K8MHZ Ham Member QRZ Page

    That has nothing to do with the point that a strike on one grounded system will raise the voltage on that entire system to hundreds of thousands of volts. Everything on that grounding circuit will have a huge voltage rise and fall while being discharged. If there is another grounding system on the same premises, the difference in voltages during a strike between the two will be huge if not electrically bonded together. If we properly bond the systems together, the entire system's voltage will rise and fall at the same time, effectively nulling out the voltage differential.

    The rise and fall thing works two ways. Not only is there a hazard when lightning strikes your radio equipment, but also when lightning strikes your electrical main's grounding system. When that happens the ground conductors from the electric supply will be thousands of volts higher than the metal connected to your separate radio equipment ground.
     
    W6KCS likes this.
  2. K8MHZ

    K8MHZ Ham Member QRZ Page

    It's all in 810.

    810.57 Exception 1, where lead in is protected by a continuous metal shield, ADU is not required if shield is grounded in accordance to 810.58.

    810.58 points us to 810.21. Everything, material, size, supports, protection, run in straight line, electrode and so forth are all covered in 810.21 and 810.58

    There is no need to look at 820 for ham radio because everything pertaining to it is in 810.

    Dereck may have a different answer, my apologies for answering him, but I happen to have a code book on my lap right now.

    Edit to add: I feel this needs to be repeated. The NEC is a book of 'what we can get away with' and not meant to be a design manual. The NEC is not a best practice book. Personally, I think because Dereck's sticky's are so well written, we would be less confused if we never heard of the NEC. Too many people errantly use the NEC to argue a point of a best practice. Again, the NEC is NOT a best practice manual. To people that haven't had the pleasure of working with it for years and wearing out a few editions, the NEC is an enormous compilation of incomprehensibility. Yes, I am quick to argue with Dereck about the details of the NEC, but when it comes down to it, Dereck will have the better answer. Dereck will give you a plan based upon personal experience and education. The NEC will give you a way out using cheaper, but legally approved methods that provide a reasonable amount of safety.
     
    Last edited: Mar 13, 2018
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    What will a 200+ foot run of #8 or #10 bonding wire from my meter ground to tower ground buy me ?

    A strike on a power pole would blow the bonding wire (Fuse) before it makes it to my tower grounding system, Because the tower is grounded better, Properly.

    You are right, I am wrong. My setup is only 30+ years old.

    I need to go inspect my tower for lightning damage and rust. :D It took a few hits.

    73
     
    Last edited: Mar 13, 2018
  4. W6KCS

    W6KCS Ham Member QRZ Page

    The NEC is what's required by any AHJ that's adopted it, it's not regulatory by itself.
     
    Last edited: Mar 13, 2018
  5. W1VT

    W1VT Ham Member QRZ Page

    If you really want to do what is best with our current level of understanding, you would be comparing different approaches using modern physics. Modern physics realizes that answers are often statistical--while you can't predict exactly what will happen, you can generate a probability distribution function to show what is highly unlikely.
     
  6. W6KCS

    W6KCS Ham Member QRZ Page

    The idea is that the more equalizing current carried by the bond, the less carried by the coax.
     
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  7. KF5LJW

    KF5LJW Ham Member QRZ Page

    Yeah I get it Steve, blame that on me and the NEC. Me for not explaining it more clearly, and NEC for making it confusing.

    810.3 means that 820.113(A) would apply and require any type of coax installed for the Article 810 application inside the building to be a listed product, however 820.48 acts as a 50' exception permitting 50' of unlisted coax in the building. So with the exemption of 820.48 means you ignore 820 and does not apply. However Once Terminated inside, or past 50 feet, you are required to use LISTED COAX of any type and now 820 would apply.

    Does that clear it up?

    I am sticking with my guns. Hams operate are under 810.
     
  8. KF5LJW

    KF5LJW Ham Member QRZ Page

    Huh? It means you have a phase shift and time delay which has nothing to do with Lightning.

    Here is a theoretical experiment that has been done many times.

    Drive two ground rods into the ground 4 feet apart, leaving the ends up high enough at waste level. Find a ham radio operator who believes grounds should be isolated. Have him/her stand between the two ground rods and grasp each rod in their hands. Now induce a utility fault or lightning strike near by. Ham Radio Operator smokes, fries, and dies.

    Now bond the two rods together with 6 AWG and repeat the test and I will gladly hold the two rods with no fear. Induce a utility fault, and nothing happens to me and I walk away.

    This test has been done thousands of times, and thousands of people have lost their lives doing it. Want to know what happens. Google "Earth Potential Rise", or " Step Potential". The distance between your feet can get you killed during a lightning or utility fault.
     
  9. KF5LJW

    KF5LJW Ham Member QRZ Page

    OK that means you are old as sin. You would have had to be 10 years old or younger putting up your tower right after WWII.
     
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    Almost.

    It was when I tuned in my favorite martian using rabbit ears.
     
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