In article ,
Jim Michaels writes:
On 18 Jun 2005 03:30:22 -0700, wrote:

Jim Michaels wrote:
Hi,

I will assume that your post is not bait and is serious

You make some good points, but there are a few I'll pick up on:


On Wed, 1 Jun 2005 10:31:18 +0100, "Christian McArdle"
wrote:

The US electrical system is simply unsafe compared to the rest of the world.

true, at least compared to UK. Maybe not the world, US seems the model
of good practice compared to African practices, and that of many other
countries.


Current, of course). Edison's first great central station, supplying
power for three thousand lamps, was erected at Holborn Viaduct,
London, in 1882. Does anyone know the voltage that was used? In any
case the U.S. Voltage is due to historical factors. I am sure the
British voltage was not selected much more recently.

but this doesnt change the fact that 110 is inherently more dangerous
than 240. With 240v we treat it with respect, with 110v people relax
since it wont electrocute them, and hurts waaay less if they get bit.
They worry less about cord grips etc. The result is fires, which are
the prime killer, not electrocution.


The basic issue is that
very few people die of electrocution, whilst loads of people die from
electrical fires. The electrical fires largely stem from high currents. If
you halve the voltage, you double the current.
NOT TRUE.
You are making multiple invalid assumptions.
1. That U.S. wiring has the same number of circuits for the same load.

still cant figure out what you mean there. For a given load you do have
higher i with lower v, and each load is on 1 circuit as far as i can
see.

UK Ten 100watt lamps at 240V equal 4.166 amps on circuit rated at 6
amps with 1mm wire.

Although lighting circuits are normally protected at 6A, the 1mm²
wiring is actually rated at 12A. The lower value protection is
required because of the choice of lampholders on the circuits.

US Five 100 watt lamps at 120V equals 4.166 amps on 15amp rated
circuit with 14gauge (2.08mm) wire.

In this example the US system has a massively greater safety margin.

Fires tend to start at wiring accessories, cable joins, etc,
and not so much in the middle of a length of wire.


2. That U.S. circuits are not designed for their load.

I dont think that was the assumption:

The proof is that you keep saying "for a given load" and the loads are
NOT the same, we have many more circuits in typical dwelling.

the problem is simply theyre
designed to have a higher incidence of faults.

Simply a system with more smaller circuits each with an equal or
greater degree of safety margin.

As an example a modest 3 bedroom suburban home normally has a 200amp
40 way main panel (CU). That is 200amps in each leg of the incoming
feed using three 85mm cables. this provides 48kW of power. This is a
home with gas space heating, gas water heating, gas clothes drying,,
and often gas cooking.
Even with our maniacal excess it would be hard to overload such a
system to the point of combustion.

Normal UK home has a 100A (24kW) supply.
If you want any more than this, you have to have a 3-phase supply,
but that's quite unusual in a home unless it was very big.

--
Andrew Gabriel