[TowerTalk] Planting Ground Rods (Long)

[Steve Miller]

Mike Foerster wrote:

<snip>
> To sink a ground rod quickly and without mushrooming the head of the ground
> rod, push the rod into the dirt as far as it will go. Pull it back out and
> fill the hole with water. Replace the ground rod, go up and down with it a
> few more times. Remove it, refill the hole with more water, and repeat. It
> works like a champ. Just watch out for the muddy water that shoots out the
> hole! If you are in real hard dirt let the water soak in the hole a few
> minutes and when it absorbs all the water put more in and then try it.

Didn't work here....

> Also:
> From: Robert L. Wieneke rlwieneke@juno.com
> 
> I use a copper pipe or tube about the same size and length as the ground rod
> with a short piece of garden hose and a female garden hose fitting circular
> clamped to the end of the pipe or tube. Then attach a on / off valve ( from
> the hardware store ) attached to a garden hose and let the water drill a
> hole into the ground. After you drill the length of the pipe or tube into
> the ground, turn the water off, pull it out and easily knock the ground rod
> down the wet hole and let it sit. After the dirt settles around it you have
> a nice tight fit.

Didn't work here....


> Ground rods are a pain in the butt. 

!!!

> Especially if one is short or the earth
> is very rocky. If you have a hammer drill available, slip then empty head
> onto the ground rod. Tape up the trigger if there is no lock on it, and lead
> the end of the ground rod into place with the hammer drill on the other. The
> hammer drill does all the work for you and will save you so much time! If it
> is going down a bit slow - leave it. The handle on the hammer drill will
> prevent the ground rod from being driven in too far.

May have helped, but wouldn't have made it to 10 feet.


dan hearn wrote:

>  I have used the fence post drivers (hollow tube with handles on each
> side from Home Depot,etc) to install 25 or so rods in Dallas and Spokane
> without any particular problems. 

May have helped, but probably wouldn't have made it to 10 feet.

>  I am also curious about the use of conductive chemicals to improve
> conductivity. I believe the Radio Amateurs Handbook has described the
> use of copper sulphate in a circular trench. Sounds like you would want
> it buried pretty deep to avoid killing the grass, Hi. Has anyone made
> measurements on ground rods installed this way?

Get a copy of MIL-HDBK-419A "Grounding, Bonding, and Shielding for Electronic 
Equipments and Facilities" available from the Dept. of Defense Automated 
Printing Service in Philadelphia, PA.  It has excellent grounding information 
including "Electrode Enhancement" (section 2.9) complete with measured 
results.

Briefly summarizing:

Section 2.9.2 Water Retention:
- overdrainage leaches away salts that are necessary for high conductivity
- channel surface drainage to keep the electrode system moist
- preferred backfill of 75% gypsum, 20% bentonite, 5% sodium sulfate (more 
    enduring and superior to chemical salting)

Section 2.9.3 Chemical Salting:
- Chemical salts in order of preference:
    1) Magnesium sulfate (epsom salts) - high conductivity, low corrosion
    2) Copper sulphate (blue vitriol)
    3) Calcium Chloride
    4) Sodium Chloride (table salt) - more corrosive, not recommended
    5) Potassium Nitrate (saltpeter) - more corrosive, not recommended
- more effective in somewhat porous soil versus compact soil
- graphs show a 3x to 10x conductivity improvement for a single rod
- somewhat lesser improvement expected for a large array of rods
- less seasonal variation in rod conductivity

Section 2.9.4 Electrode encasement
- use conductive mastic or conductive concrete to improve rod to earth contact
- encasement material that absorbs and hold moisture is preferred

Section 2.9.5 Salting Methods
A) Circular trench about 1 foot deep, 2 feet dia. around the electrode partly 
   filled with salts then covered with earth
B) Bury a 8", 2 foot deep tile pipe in the ground surrounding electrode with 
   salts in the bottom foot of pipe thoroughly watered in. Cover the pipe at 
   ground level using a wooden cover with holes drilled in it

Both methods A & B require 40 to 90 pounds of chemical to maintain effectiveness 
for 2 or 3 years. Chemical replenishment are required less frequently with age.

C) Hollow electrodes filled with salts with breather holes. Atmospheric moisture
   is absorbed converting the salts to an electrolyte the seeps through holes 
   in the electrode into the surroiunding soil.




Two weeks ago, I finally broke down and hired a pier drilling company to drill 
holes for my ground rods (9 for the tower, 4 for the house entrance). It took 
over 3 hours (about 15 minutes per hole) with a 17 ton auger drilling rig 
using a rock bit! If it ever cools down enough (near Dallas), I'll start 
installing the copper:

My ground system design uses 3/4" (7/8" O.D.) copper water pipe for the ground 
rods and radial arms. All connections are brazed and made using standard copper 
pipe tees and couplings although the tower leg connections might be clamped with 
a stainless steel shim between the copper pipe and the tower leg. A 4" dia. 
drainage tube will serve as a temporary form for an 80% powdered gypsum, 
20% bentonite electrode backfill with the remainder of the 12" hole back-
filled with the material removed during drilling. The ground rods (pipes) 
will be closed at the bottom, filled with magnesium sulfate (epsom salts) 
and have holes drilled every foot to allow the epsom salts to leach out 
and increase conductivity around the rods. Once the local watering 
restrictions are lifted, everthing will be soaked in real good and I'll be 
able to rest easier during thunderstorms.

Hope someone finds this useful....


-- 
Steve Miller   N8SM   millersg@dma.org   http://www.dma.org/~millersg

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com