In article , (Chris Lewis) wrote:
Most people tend to think that grounding rods and the like have very
low resistance (as in zero). They do not. The grounding-rod to dirt
resistance
can be surprisingly high. For example, a NEC-satisfactory grounding system
can have _more_ than 25 ohms to dirt. A dead-short to dirt could
only push 5A or so at 120V. Not even enough to trip the breaker.

I believe the NEC recommends driving a second ground rod, if the first
measures more that 25 ohms. I can't remember if you are supposed to do
anything else if you still have over 25 ohms.

In telephony-land, cell sites usually are required to have 5 ohms or less. Of
course,they come with 100 ft+ lightning rod, known as the cell tower. :-)

-don