volts500 wrote:

To make the same earthing sufficient for transistor safety means both
meeting and exceeding post 1990 National Electrical Code. Therefore an
earthing wire must be even shorter than required by code - 'less than
10 feet'.


The NEC actually does require, in NEC 250.30(A)(4), that the grounding
electrode to be "as near as practicable" and "preferably in the same
area" as the grounding electrode conductor.
The NEC can't dictate where a utility will bring in it's service. In
my house, for example, the electric and phone comes in on the right
side of the house, the water comes in the front, and the cable comes in
on the left side of the house, all due to the physical layout of the
utilities.

The IEEE guide on surges and surge protection:
http://www.mikeholt.com/files/PDF/Li...ion_May051.pdf

starting on guide page 31 shows the problem of having power H-G bond
point and CATV protector block connected with a long wire - potentially
many thousands of volts between the power wiring and CATV lead. The fix
in the guide is to use a plug-in suppressor that has both power and CATV
wires go through it - the voltage on power and signal wires is clamped
to the common ground at the surge suppressor. Another fix would be to
route the CATV wire from the entrance ground block to the power service
and install a 2nd ground block with short earthing connection to the
power grounding electrode conductor coming out of the service. Then
distribute the CATV from that point. Same with phone, dish, .... IMHO a
single point ground is more important than the resistance to earth.


I would like to see the NEC require a Ufer ground, though. IMO, a
ground rod (even two, 6 to 10 feet apart) is about the worst grounding
electrode permited by NEC. A Ufer ground (concrete encased electrode)
is easily installed during new construction, and there is no real
excuse, other than laziness, NOT to install one.

Totally agree. Apparently 250.50 starting in the 2005 NEC is intended to
require Ufer grounds in new construction where there is a concrete
footing or foundation. IMHO the requirement is not at all clear and is
more apparent in the exception than the rule. I don't think it was noted
in code change material I read.

--
bud--