[TowerTalk] Ground rod sticker shock

[Jim Lux]

At 01:28 PM 11/9/2004 -0800, Daron J. Wilson wrote:
>Sounds pretty good, wonder if you should share your 'experience' with
>the folks at the National Fire Protection Association, National
>Electrical Code, ANSI, IEEE, and all those kind of places?  There must
>be some reason they approve what they do, and it is usually due to a
>large amount of testing and evaluation.
>
>Sure, copper pipe might work fine, so long as your insurance agent is
>willing to pay out for your lightning damage even though your
>installation doesn't meet the recognized codes.  I dunno, it just isn't
>worth it to me.
>
>Daron J. Wilson, RCDD          ) )
>Telecom Manager               ( (
>LH Morris Electric, Inc.       ) )
>(541) 265-8067 office       _|****|  mmm!
>(541) 265-7652 fax         ( |    |  coffee!
>(541) 270-5886 cellular     \|    |
>daron.wilson at lhmorris.com    |____|

Copper pipe would be accepted under the code if properly 
installed.  Without checking the code, off hand I would say that burying it 
in a trench would meet the requirements.


If one is talking IEEE Std 142-1991 (the "green" book), chapter 4 goes into 
a fair amount of detail about what is acceptable for grounding 
electrodes.  What you are talking about with either ground rods or copper 
pipe is called a "made electrode" (differentiated from using something 
that's already there, such as well casings, piping, etc.). Section 4.2.2 
talks about Driven Electrodes.  Then, there's the ever popular Concrete 
Encased Electrode (aka the Ufer ground).  Finally, there's the 4.2.4 "other 
electrodes" which refers to "buried metal strips, wires, or cables". "The 
depth at which the strips are buried may not be critical.... Tests by the 
NBS show that resistance decreases only about 5% when burial depth is 
increased from 18 to 36 inches. Similarly, the effect of conductor size is 
extremely small."

Section 4.3.1 talks about choice of rods and mentions that the reason for 
copper coating is NOT to make a better contact with the soil (there's lots 
of surface area), but to make a better contact with the (presumably) copper 
grounding wire.

The code requires 8 buried feet, so the 10 foot standard rod gets you there 
with 2 feet above ground to make the connection.