RE: Ground rod question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-hp-dot-com>

 >Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
<Mddeming-at-aol-dot-com>
 >
 >Hi Gary, All,
 >        Brine (salt + water) eats concrete as well as many metals. It also
 >kills tree roots, shrubs and grass. Burying in the dirt should be adequate.
 >I would use salt only as a very last resort if nothing else worked.
 >Matt D.



Yes, despite persistent references suggesting the use of rock salt, your 
point and Ed Sonderman's experience would suggest that NaCl should be 
avoided.  Doing some Google searching I came across this.  It looks like 
Epsom salt is the best salt to use.  I'm not looking to go nuts over this, 
especially since it won't make any difference to the length of my 
sparks.  I've perforated the buried 10 foot horizontal pipe segment, so 
I'll be able to pour in a saturated solution of Epsom salt from the top, 
should I feel the need to.

Gary Lau
MA, USA

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============================
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.
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 > I'm having some new construction done on my house adjacent to my garage
  > involving a new foundation, and this presents an opportunity to construct a
  > better RF ground system than the single 8 foot ground rod I presently use.
  > The footings are about 5 feet deep, so I was planning on having an "L"
  > shape of 1/2" copper pipe, 5 feet vertical, down to a horizontal 10 foot
  > segment laying beside the footing.  I also soldered on a 1 foot by 2 foot
  > sheet of copper roof flashing to the base of the vertical segment.
  >
  > My question is, would it be better if the horizontal segment were cast
  > within the concrete footing, 5 feet below the surface grade, or would it be
  > better to just lay it in the dirt beside the footing before backfilling?
  > If the latter, would there be a benefit to applying a healthy dose of rock
  > salt about the pipes prior to backfilling?
  >
  > Thanks in advance,
  > Gary Lau
  > MA, USA