At 08:50 -0700 24/7/09, Todd Cory wrote:
I have heard that this requirement (to bond negative to ground) as
well as bonding one of the AC conductors to ground (neutral wire)
was pushed through by wire manufactures and unions. The wire manus
sell more of their product and the electricians get more labor in
installing them. I also agree that grounding any live conductor
actually makes the system less safe.
My understanding is that it saves cost to ground one of the
conductors. Then you can use single pole switches, fuses and
breakers. If both of the circuit conductors are 'hot' then you will
need to use double pole everywhere.
When I have traveled over seas, I always try to open the main panel
to see how things are laid out. They never associate one of their
power conductors (usually 240 v) to ground.
Here in the UK there is no need to ground the neutral in the panel.
It has already been done by the utility at the transformer. With the
result that a lot of electricians think that neutral is in some way
intrinsically grounded and the hot wire is intrinsically hot. They
don't know about making their own bond on a stand alone system, and
start digging bigger and bigger holes in the ground instead. Hoping
for a better ground...
You can test whether the neutral is grounded quite easily with a
multimeter. I believe that everyone does ground it. Everywhere that
I ask it turns out that it's been grounded. Here we lately have a
new wiring system called Protective Multiple Earthing where the
ground and neutral are combined into one wire (saving on cost). This
has the interesting side effect that the whole house will become
'hot' in the event of a failure of this one conductor.
--
Hugh Piggott
Scoraig Wind Electric
Scotland
http://www.scoraigwind.co.uk
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