Roy Lewallen wrote:
Dave Shrader wrote:
. . .
A major point of caution is required. The NEC requires ONLY ONE
ground connection. Multiple ground connections introduce VERY SERIOUS
ground loops that may violate the NEC criteria. This opens a VERY
LARGE loop hole in your home owner's insurance policy. If you are
adding a second earth [ground] connection at your station use an
isolation transformer to break up the ground loops in the basic 120
VAC connection. Consult with an electrician regarding your local and NEC codes.
. . .

My NEC book is getting pretty old now, 1990, but at that time, multiple
grounds were often not only permitted, but required. And a *minimum*
spacing was sometimes specified.

For example, section 250-84, Resistance of Made Electrodes: "A single
electrode consisting of a rod, pipe, or plate which does not have a
resistance to ground of 25 ohms or less shall be augmented by one
additional electrode of any of the types specified in Sections 250-81
or 250-83. Where multiple rod, pipe, or plate electrodes are installed
to meet the requirements of this section, they shall be not less than 6
(1.83m) apart."

Is it something like this? Multiple ground rods are permitted
(encouraged, even) in order to establish one good ground connection; but
the wiring system can have only one ground connection.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek