Grounding Do's Don'ts & Why Part 3

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KF5LJW, Mar 19, 2012.

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  1. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Very interesting, I'd never considered how much current might flow in the ground relative to the wire, though I was aware it existed.

    Doing a little napkin algebra (very iffy early in the morning!), the ratio of the total wire resistance to total ground resistance is proportional to the square of the line length. Using your numbers, a short single phase distribution line of only a couple of miles won't have much ground current because the total parallel ground resistance is still high compared to the wire, and most current is still carried in the neutral. Which is good for me because that's how our area is wired.
     
  2. KF5LJW

    KF5LJW Ham Member QRZ Page

    Of course the close you are to the sub-station, the stray voltage is less of an issue. Take note in W9JEF case he has a single lateral line rather than 3 phase where most neutral current is balanced out. It is a real concern for farming operations like diary production, or live stock water tanks with heaters. The animals will receive a mild shock and will not drink or produce milk.

    On another note for ham radio operators this is directly related to station grounding where misinformed operator will install a ground system and not bond it to the AC service ground. You create a difference in potential between your equipment and radio ground which can wreak havoc on your radio, and god forbid you have a nearby lightning strike where the potential difference surges to thousands of volts and have a Flash Over inside the shack.
     
  3. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    How long is the single phase distribution line from you home to the three phase line?
     
  4. W9JEF

    W9JEF Ham Member QRZ Page

    The closest 3-phase is the KMCK FM antenna tower (that I had erected) 4 miles to the west, where Old Highway 68 merges with US 412. We have substations to our east, and west, about 10 miles in each direction.
     
  5. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Ok not terribly long then. I’m estimating ours is about 1.5 or so.
     
  6. N4EL

    N4EL Ham Member QRZ Page

    Dereck,

    Many thanks for your 3 posts on grounding and answering questions on the topic for the last 6-7 years! I now realize that my station "grounding" is woefully inadequate and I have been lucky that my equipment has not been damaged by lightning in the past!

    At present, I am using a ground-mounted vertical. The coax from it enters the house via a foundation vent and then runs through crawl space to the unfinished basement. My station is located in the basement on the other side of the house from where the coax enters and is about 6 feet from the AC service entrance panel. I hope to add a tower and beam with the associated coax and rotor control cabling in the not too distant future.

    My plan to upgrade my grounding is to do the following:
    1. At the outside of the foundation vent, insert a coax surge protector such as a PolyPhaser unit into the coax run. I'll mount the protector to a grounding panel in a waterproof enclosure and ground the panel via a ground rod that will be connected/bonded back to the AC service entrance ground rods (using #6ga copper wire and additional ground rods to cover the distance around the house). When needed, additional protectors could be mounted on the panel if additional antenna systems are installed.

    2. Inside the house on the wall above my station desk, add a single point ground panel that will contain a second coax surge protector
    (secondary to the primary one outside at the foundation vent) and a 120V AC surge protected outlet (e.g., one of the Tripp Lite ISOBar units).
    I will leave space on the panel for future expansion if I add antennas.

    Questions that I'd appreciate responses to:
    1. Thoughts on my plan, above?

    2. How should I connect the inside panel to ground? I see 2 approaches: Run a grounding wire through the outside wall to the panel's "own" ground rod that is also bonded to the AC service entrance ground rod that would only be a few feet away. -or- Is it possible/advisable to connect the panel's ground wire to the ground wire coming out of the breaker panel before it leaves the inside of the house or even to connect to the breaker box itself?

    3. I operate a tube-based amplifier that runs off 240V. I would think that the 240V circuit receptacle should be on the single point panel with a surge protector similar to the 120V side. If so, I can't find a similar 240V protector/outlet that uses the typical US NEMA 6-15R receptacle. Any suggestions?

    4. Would adding a "whole house" TVSS eliminate the need to surge protect the outlets for the station that otherwise would be
    on the single point ground panel (and would it solve my "how do I do 240V TVSS question above)? What rating for a whole-house TVSS should I look for?

    Many thanks for your help and suggestions.

    73, Nat N4EL
     
  7. KF5LJW

    KF5LJW Ham Member QRZ Page

    You are welcome and my pleasure to help

    I think you are on the right track so far and have done your homework. Cuddos.

    You have two choices, either Single Point or Multi-Point. I think it might be possible to do Single Point, but not certain. Single Point is the best and Multi-Point is a compromise. More on that in a minute or two.

    For now I am just going to comment on the TVSS approach. 95% of all lightning damage is via Utility. 9 times out of 10 lightning will strike the utility on the primary side of your service transformer. What this meas to you is the surge is in the Differential Mode or Phase to Phase as opposed to Common Mode Phase to Ground. So before you spend a penny on a Class C device (aka Point of Use or Power Strip) Invest in a Whole House TVSS at your service entrance. Class C Power Strips and not made to handle Utility Surges, only to suppress what a Class A device Lets Through. Th ebest kind of TVSS are ones you buy through the POCO known as a Meter Collar. Just as the name implies, the POCO unplugs your meter, plugs in the TVSS Collar, then plugs your meter back into the TVSS Collar. So if you can only afford one, go with Whole House. Otherwise you are just throwing money away.

    As to the rest of your questions rather than take days airing dirty laundry on the forum how about one-on-one conversation? I have way too many questions and need a clearer picture. Send me a PM and I will give you my phone number and we can work out a time to talk things through.

    One thing I will say is if you need a 240 Circuit, run a dedicated circuit and I got a very good idea you may like. In any event you will want a dedicated NEMA 6-15 or 30 amp just like an electric dryer circuit would use. Ideally you want a dedicated 120 volt circuit if your breaker panel has room.
     
  8. N4EL

    N4EL Ham Member QRZ Page

    Dereck,
    Thanks for the quick reply. Many thanks for wanting to follow up! Sorry for being dense, but how do I send a PM to you? Can't find your email address in your QRZ page and the help files have not helped ....

    73, Nat, N4EL
     
    Last edited: May 30, 2019
  9. W9JEF

    W9JEF Ham Member QRZ Page

    Why not share our discussions? Surely the grounding issues that arise at one QTH are not uncommon at many others.

    :cool:
     
  10. W3TDH

    W3TDH Ham Member QRZ Page

    I have built communications installations from Tierra del Fuego to Alaska and from French Frigate Shoals to North Africa. With every job we used the techniques that the original poster is outlining and I never had a lightning caused failure. On the UN demonstration project we did on Village Power Systems; including wind power; the installations ran for years without a lightning caused failure. The UN demonstration projects were done on a least cost basis with sections of copper pipe used as ground busbars and similar approaches. Keep in mind that we were competing to be the prime contractor on deploying the UN demo installations more broadly and we won the competition. I was admittedly pretty disappointed when the projects funding was cut. My point is that it is doable and not super expensive to follow this guidance. What really stands in the way of doing it is not the effectiveness but rather the typical ham's unwillingness to do the trenching and other physical work that the installations require.

    W3TDH
     

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