Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AI5DH, Feb 28, 2012.
Damn, where are the sticky buns?
All this sticky talk is making me hungry.
I'm a bit confused about his. I live in one of those places where the soil is very sandy. I can push an 8-foot ground round about 3 feet into the ground with just my hands. I currently have a total of 7 ground rounds, 4 around the tower, one between the tower and entrance and two just outside the shack entrance. Everything is bonded together and I have panels with lightning arrestors at both the tower base and shack entrance.
I was actually thinking of placing 3 more rods approximately 16 feet from the others around the tower and bonding all those together (these are 8-foot rods).
Lightning here in Florida is a daily occurrence and a gazilion strikes!! Is it possible to have TOO MANY ground rods that creates problems??
Quote: "Lightning here in Florida is a daily occurrence and a gazilion strikes!! Is it possible to have TOO MANY ground rods that creates problems?? "
No, You can keep adding more and more, But when you get much further than 75 or so feet out away from the tower they will not be doing much good.......
Usually, After about a dozen or so you start to reach a point of very diminishing return for the money and effort spent.
Anyhow, Proper BONDING of all the ground systems with good low inductance conductors is lots more important than how good the ground is.
No Bob you can put in as many as you can afford, but there is a point where it does no good. For simplicity follow this rule for ground rods spacing should be equal to the length of the rod. So if you are using 8 foot rods space them at 8 feet.
The old logic use to be twice the distance of the rod length but that has proven to be less effective because of the added inductance incurred from the longer bonding jumper. In your case Bob if I were you I would call my county extension off and find out what depth the ground water table is. So if it is say 10 feet, I would be using 16 foot rods
Also keep in mind all I can present here is minimum requirements, it is up to the user to decide what extra steps they can afford.
For example here is a tangent. Depending on how your tower is constructed , a ground rod at the tower base or legs could be a complete waste of time and material. Shocking? Heck no it is not. If your tower is constructed using a concrete blocks in the ground to support it, all you need to do is bond the anchor bolts and reinforcement steel, then bond a minimum #6 AWG jumper to the reinforcement steel to tag a leader out to be bonded to the rest of the GES. A concrete Ufer ground electrode is the best electrode money can buy, and one of the least expensive to implement. NEC requires it for all new construction but it is a scaled down Ufer electrode called Concrete Encased Electrode.
But the whole point of a Ground Electrode System is to provide a planned discharge path, with enough current handling capacity to earth, and keep as much of the fault current outside as possible. From there when it arrives at the entrance point of the building, lightning see's a high impedance. So the end result is the GES presents a low of impedance we can make it, and make the entrance a beyond as of high impedance we can. Basically you are making 1 big shunt, and shunting lightning current to ground, or I should say earth.
Dereck and the Group: I present multiple questions not to create unrest nor be a pain in the patootie -- simply for clarification of terminology as an aid to the new folks and we old folks as well (we do tend to live with definitions for decades and be wrong the entire time)
"Bonding" via "Exothermic Welding" ..... "Exothermic Bonding" .... "CADWELD Electrical Grounding and Bonding".
"Bonding" via a mechanical CLAMP.
I would guess many if not most of us utilize a "mechanical clamp" to connect some form of "wire" in various forms, be it "round wire", "flat strap" (metal plumbers 'tape' with or without a copper 'coating' of some sort) -- copper tubing -- webbed ground-strap or a variation of same etc etc).
While the term "bonding" is used extensively and may be a given for some folks as to what it actually entails, others may take it to mean the "mechanical clamps" available at home-stores.
Clarification may be in order (or not) as to exactly what is meant by "bonding" AND IF single OR multiple "mechanical clamps" are sufficient when used to 'connect' these various "ground systems" together.
Lastly (for my query in any event) is: "Bonding together" - be it via the 'heat-generated' methods or 'mechanical clamps' would be this:
(1) - Home with NO ham radio has an existing 'ground point' at the service entrance.
(2) - Ham moves in and puts in a RADIAL SYSTEM along with his antenna, feedline etc etc.
(3) - Ham installs a "ground system" consisting of say six "ground rods" connected by one of the aforementioned methods. He (or she) DOES connect this "ground system" DIRECTLY to the SERVICE PANEL GROUND POINT --- BUT does NOT connect the three "ground systems" TOGETHER.
Now we have THREE systems -- NOT CONNECTED TOGETHER (NOT electrically, thermally or mechanically bonded as the term is used in the articles).
My understanding in Part One and as referred to in Part Two is this:
(A) - SOME folks say ALL THREE SHOULD BE CONNECTED ("bonded") TOGETHER.
(B) - OTHERS SAY they should NOT BE CONNECTED ("bonded" TOGETHER.
Potential point of "confusion": Should ALL "ground systems" BE "connected together" or does simply running each to the "Service Panel Entrance Ground" suffice (by either the thermally generated OR mechanical method)?
OR -- ALL should NOT be "connected together" and then run to the "Service Panel Entrance Ground" by one of these methods?
I am not trying to generate unrest nor be a general pain in the patootie; simply think clarification of the METHODS and exactly HOW these "bondings" are made. Again - thermally or mechanically. IF mechanically --- are the "clamps" acceptable? If so - are multiple clamps beneficial or REQUIRED?
Excellent points by all thus far and I have read each one which has resulted in the POTENTIAL misunderstanding of the terminology I have cited. Perhaps only on MY part - perhaps by others. Thank You all for any additional opinions - facts and methods of making these 'bondings' a plus for safety and station performance.
I hope my queries are not confusing. I know what I wanted to ask and hope I properly worded each question so as to not be confusing to the group / discussion progression.
Dirty Don - Old and Getting Moreso Every Day!
You can always go to chemical ground rods to improve the grounding. There are all sorts of commercial versions available or you can build your own.
For lightning protection you can go longer. For r.f. grounds, 5 feet will get you basically the maximum effective grounding.
Fill the rods with rock salt, epson salts, etc.
No problem my friend I enjoy answering good questions.
To clarify bonding has nothing to do with the physical method of electrically joining parts. When I say BONDING I am using a defined electrical term:
Bonding = Connected to establish electrical continuity and conductivity.
Bonding Jumper = A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected.
But you bring up a very important question. The pros only use exothermic welding, or irreversible hydraulic compression of 14 tons. They do so because it will never fail. Unfortunately that is not possible for most HAM operators unless you hire someone with the tools and equipment to do it for you. Unfortunately I can guarantee just about all mechanical connectors are going to fail. The worse offender is split nuts
OK I am typing slowly so everyone will clearly understand me. ALL OF THE ELECTRODES SHALL BE BONDED TOGETHER TO FORM A COMMON SINGLE GROUND ELECTRODE. That means the AC Service Ground, Lightning Protection, and any RF radials ran on the ground SHALL BE BONDED TOGETHER
Anyone who says differently has no clue what they are talking about. Failure to do so puts your life in great danger including your equipment and operations. All electrical codes, engineering standards and implementation practices clearly state this fact. I will even go so far to say anyone who does recommend them to be isolated, the Moderators should delete their post, or else the owners of this Forum can be held liable. I know for fact they can because I am a Moderator on Mike Holt's NEC Code Forum and it has happened to Mike when we missed post that clearly does not comply with electrical codes.
I am not trying to be JERK about it, but I want to make that point very clear. I have already cited the Code articles that clearly states that point.
Well I can talk about that if you guys want, but do not use Rock Salt. It works but it will eat you conductors and self destruct. Epson Salts and Calcium Chloride are good to use. But one of the best things to use. especially for back filling and doping holes with is Bentonite Clay. It is dirt cheap sold in 50 pound bags. It has a few different names like Drilling Mud, and your wife Make Up she puts on her face.
When you install a Chemical Ground Rod what they will do is Auger out a 8 inch hole 10 feet deep. Set the rod down in the hole and then back-fill with Bentonite Clay and use water to pack it in.
In Data Centers and Cellular Shelter sites we use a lot of Ground Rings using 2/0 in combination with 20 foot ground rods. We excavate a trench around the building, lay the 2/0 in and cover it up with Bentonite Clay, and dope it with Calcium Chloride. You can use the same technique with radials and bonding jumpers if you desire.
An even better "fill" is lignite. That is a "soft" form of coal which is strip mined in several areas of the country, east Texas being one of the principle sources. Lignite has a higher conductivity than bentonite. However, lignite is not commonly available, at least no where near as available as "drilling mud".
During my tenure with Texas Utilities, lignite was widely used for grounding installations in areas where chemical grounds were needed. Now lignite was basically a zero cost item because TXU was mining hundreds of tons a day, at several mine sites, for use in their east Texas electric generating stations. I don't know about today, but in the 1990s TXU was the largest coal mining operation in the entire Western Hemisphere! Since all of the coal that was mined was used only by TXU, the extent of the coal mining operations was not widely known outside of the coal mining industry.
Bentonite clay is dirt cheap?
Who would have thought.....