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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

    And the fact is the NEC requires all grounding systems on the premises to be bonded together with appropriately sized conductors and listed connectors.
     
    KC9VFO, WA7PRC and W6KCS like this.
  2. KV6O

    KV6O Ham Member QRZ Page

    Like anything learned over many years, it's an iterative process. New information creates changes in how we view things. The tower wind loading "process" continues, I attended a presentation from one of the steering committee members of the TIA-222-H tower standard, and there are lots of changes on how you analyse towers for wind loading. We continue to learn new things and apply these things to the standards. Grounding is no different, Motorola's R56 standard, widely used here in the US continues to evolve. Other countries do it differently, electrical code and grounding standards in Asia are different, for example. Not wrong, just different approach.
     
  3. W6KCS

    W6KCS Ham Member QRZ Page

    None of what I posted is my opinion, it's right out of NEC 250, 810 and 820. The codes do evolve, but they aren't going to evolve to the point where they allow you to separate your cable entry and service ground. Good luck finding a bonding path. A water jet works wonders for tunneling under sidewalks and driveways.
     
    Last edited: Mar 10, 2018
  4. W6KCS

    W6KCS Ham Member QRZ Page

    It's required to be bonded to ground close to where it enters the building. If you do it at the ground rod outside the shack, that would at least give that ground rod a reason to exist. Here's an easy to understand explanation of the codes that apply and what you need to do:

    https://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/Article820CodeBasics~20030214.htm
     
    N0TZU likes this.
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    Where is transmitting stations mentioned ? What is limited-energy coaxial cable ?


    Be careful with limited-energy coaxial cable.

    It’s easy to misinterpret 820.1 as limiting Article 820 to television or cable TV applications. But, it applies to any work you do installing coaxial cables to distribute limited-energy high- frequency signals. For example, if you’re installing coax for a closed-circuit television in a security system, Article 820 applies (see Figure 820-1 un820-01 820-01 01.cdr). If you use coax to connect antennas to equipment [810.3], or for local area networks, you must follow Article 820 (see Figure 820-2 un820-02 820-01 02.cdr).
     
    W6KCS likes this.
  6. W6KCS

    W6KCS Ham Member QRZ Page

    The codes only apply when receiving :)
     
  7. WB4SPT

    WB4SPT Ham Member QRZ Page

    I hate to be the bearer of bad news, but your NEC rule set is not "designed" to protect your radio shack from calamity from a direct lightning hit. So, the running of the 6awg to the service entrance, the tying in of the outdoor aerials, and the use of so-called lightning arrestors will just lead you down the legal, but non-the-less, the garden path.
    Quite a high percentage of my time is spent designing electronic systems that are tolerant to very close lightning strikes within substations. I don't work with the ground grid design itself, but my equipment does tie into it.

    There seems to be a chronic lack in many of the previous posts about the fundamentals of lightning current dissipation and lots of discussion of what to do with the leftover current flow into the service grounding electrode.
    In its simple form, you need ground rods at the likely point of lightning impact, and lots of them. For most of us, that would be at the antenna. At the base of a tower, at dipoles strung up in the trees, and beverages attached to fences. For a fairly simple antenna farm, be thinking 5 to 8 rods. All outside, none in the basement, none under slabs, all below the antennas (shadow). Rods are cheap, buy a bunch and bang them in, spread them around, and tie them together.

    OK, so you have now dissipated maybe 80% of the strike current. There will always be some left. THAT is the current you are heading INTO the house, thru the electrical and plumbing service with this famous #6 solid wire. You need to MINIMIZE this current, not MAXIMIZE it. Lets think why. As you inject the last 10kA of lightning current into your load center, the following will happen.
    • Lots of current will flow towards your service drop and your shared transformer. Most of the current will flow into the neutral wiring and flow down into earth through multiple vertical grounds, if overhead drops. Pad mount transformers have also grounding systems, locally.
    • Lots of current will ALSO flow into your service grounding electrode, and probably your metallic water tubing/pipe.
    • Your load center will distribute to all branch circuits a high potential spike on neutral and ground conductors. Probably much less on the Hot/line conductors, the beginning of differential mode trouble.
    • Your cable modem, being at the house electrical ground potential, now tries to inject LOTS of current upstream via the RG6 shield.
    • The combined effect here is a raising of your house ELECTRICAL ground level, far above normal. But, many metallic items will remain at the mostly normal electrical level.
    • Expanding on the last point, you will find a large differential voltage from outlet grounded yokes to steel framing, from garage door grounded openers to the ungrounded tracks, from grounded vent fans to their metallic floating ducting, from antenna masts to ungrounded aluminum sided, to note just a few of many points of interest. All of these points become a source for further trouble. Sparks over drywall into attachment screws, blown out GD openers, blown bath fan controllers, blown cable modems all the way to the street level multiplexor, I have seen personally.
    There also exists quite a level of resignation about God's will and the futility of lightning mitigation. My only comment there is that lightning comes in sizes, just like every other meteorological event. Most lighting bolts don't melt 1/4" steel plate, although a few can and do. Wind can go to 250mph in almost every area of the country, yet the odds are very low and we don't design houses for it.
     
    Last edited: Mar 11, 2018
    K4SAV, KD4MOJ and WA7PRC like this.
  8. K8MHZ

    K8MHZ Ham Member QRZ Page

    Amateur transmitting stations are covered in PART III - Amateur Transmitting and Receiving Stations. 810.51 requires compliance with 810.11 - 810.15. 810.15 requires masts and metal structures to be grounded as per 810.21.

    I don't know why 820 was mentioned, as it only applies to distribution systems.

    820.1 Scope. This article covers coaxial cable distribution systems of radio frequency signals typically employed in community antenna (CATV) systems.
     
    Last edited: Mar 11, 2018
    WA7PRC likes this.
  9. W1VT

    W1VT Ham Member QRZ Page

    You may want consider the possibility of designing your station for remote operation. DXCC rules currently allow you to work countries via a remote controlled station,. Most hams consider it acceptable to work new ones from your own station remotely, even if you aren't sitting in front of the radio. This can allow you to work DX while on a business trip or vacation overseas. A WiFi or internet link may be a practical way of connecting the control point to the RF hardware.
     
  10. W6KCS

    W6KCS Ham Member QRZ Page

    Because when 810 discusses coax entries, it refers you to 820. 820 also covers antennas.
     

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