dave wrote:
On Tue, 04 Apr 2006 14:09:52 +0100, Andy Wade
wrote:

dave wrote:

I have some questions regarding domestic electrical earthing - and would
appreciate some enlightnment.
Mmm while I thank you for the purely informative parts of your reply I object to
your presumptuous and patronizing statements.

Fie!

You are receiving excellent expert advice.

My first impression from your post was that you have an elderly
TNCS/PME supply, so may be AW is a little alarmist, however it is also
clear you have some homework to do to familiarise yourself with the
theory and practicalities of domestic power wiring.

snip....

.. I am more than happy to debate
electrical theory with you (if I have the time anyway).

snip...

.. I have been involved in electronics for 30
years

There is considerable difference between electronics and power supply
practice.

Ohms law stays the same, but after that everything is at opposite
poles: eg

generally in electronics: currents are low; conductor size is seldom
critical; frequencies may be high; impedances contain R,L & C
components; compenents get hot but conductors don't; heat is dissipated
with fans; circuit fault protection is ignored.

in power supply work (at least for domestic and small offices) :
currents are high; corrrect conductor sizing is vital; frequency is low
and fixed (50Hz); impedance is pure resistance; components (fittings)
stay cool but conductors get hot; heat is dissipated to ambient
surroundings (and thus much attention is paid to routing conductors);
circuit protection, especially from unforseen external causes, is
important.

There is also a significant difference in bonding practice: in
electronics common practice is to bring all grounds to a common point
and avoid mesh circuits because of eddy currents: in power supply work
everything in sight is bonded at every opportunity creating a huge mesh
network.

it might help to peruse:

http://www.kevinboone.com/cableselection_web.html + other items on
Kevin Boone's website. [highly recommended if you are know your elec
theory but are new to power cable selection and protection].

IEE On-Site Guide

The Electricians Guide John Whitfield

HTH
..