"Big" copper is safer. More surface area contacted on ANY given
wire nutted union! I'll stick with my low resistance, yet higher
current capable big stuff, and let the breaker box manage the shorts
instead of the wire in the wall managing a fire, thank you.
The lower voltage is safer as well.
On Thu, 22 Jun 2006 04:40:04 GMT, Roy L. Fuchs wrote:
And what defines "big"? Right... Current, or more precisely: current
Surely a 50 amp bussbar looks HUGE when only supplying a 15A circuit,
but that perspective quickly changes when you try to bolt the very same
bar into a 4kA feed ;-)
Half the surface area @ half the current = same current density. So the
difference for well-made connections is nil.
For a faulty connection OTOH, things get a lot dirtier (for 120V, that
is). Since faults are non-linear in nature, 240V faults will develop
_much_ more heat than a 120V one (often by a magnitude). This might look
horrible, but it _actually_ means that, in 230..240V-land, most faults
literally go out with a (firecracker-like) bang, either clearing the
circuit or tripping the breaker immediately!
Granted, it scares the cr*p out of people IF it happens, but I somehow
prefer that over 'silently arcing, while lighting yet another electrical
Well, practice what you preach, then!
In practice, however, you'll end up terminating those thicker wires into
gear that (from a .eu perspective) can only described as dangerously
flimsy, despite having to handle twice the current. So much for
Obviously, wire size is still _the_ criterium for rating the breakers.
You'll need less current, so it trips at less current... There is
absolutely no practical difference WRT short cicuit conditions.
In a 'bare wire to bare wire' comparison it surely is, but:
Using 'lower voltage' and 'safer' in the same sentence for something
that's NOT <42V @ moderate currents, is only self-deception. It's a
breeding ground for complacency!
I, personally, fear complacency (and complaceny-induced lax quality (on
safety-critical components) standards) much more than a small appliance
running off 230V, which had to withstand a 'both prongs floating @ 4kV'
insulation test. But YMMV...
On Fri, 23 Jun 2006 06:27:03 GMT, Roy L. Fuchs wrote:
< big snip >
Well, bare wire == people contact is highly likely. Probability of
contact is a thing that _should_ be factored in, when talking about
As a certain Georg Ohm discovered ages ago, voltage and current are
And 42 is not only the answer to life, the universe and everything, it's
also generally regarded as THE voltage limit, where human contact won't
result in a lethal current in ANY circumstance. With everything over
42V, _avoiding_ contact should be the #1 priority!
If that isn't 'complacency' spelled out in 400 point, all-caps, bold and
You should ;-)
From my experience, 230/240 feels like a much better 'wake-up call'
Remember: Electricity doesn't kill people, complacency does!
Uh, last time I've checked, this was an EE group. I find the lack of
basic knowledge on insulation testing disturbing.
Designing an appliance to withstand a 4kV insulation test doen't require
magic, nor exotic materials. Using at least two layers of insulation
(which could be anything, including air) and ensuring sufficiently long
current creep paths everywhere, does.
But that's obvious to everyone who has read the EN60065 code for 230V
As it relates to heart fibrillation, only current matters.
Regardless of what voltage someone has introduced into their body,
all that matters is how much current passes through the heart.
That has to do with pathways, and the initial voltage IS a factor
for any given skin resistance. So 120V WILL be safer than 240V for ANY
given test circumstance.
So, yes, very much correlated.
You got it wrong. It is 42 mA.
In a closed body, a 42mA current can fibrillate the heart.
In an open body, heart DE-fibrillation is done at 2mA levels with 2"
paddles. It's all about the current.
AGAIN, current is the main factor. A 5000 volt power supply that is
limited to 1uA current will not harm anyone, even those an arc from it
might not feel the best to the person receiving it. That 5000 Volts
got clamped to near zero at the onset of current flow in the completed
What I would do:
Everything would be made to operate from 240V.
The 240V would be supplied from center tapped transformers, with the
center tap grounded. In other words, the current American system.
The center tap would be used for nothing but grounding. No 120V devices.
3 phase would be 240Y/139, with the Y center point grounded. Again,
everything uses 240V either single phase or 3 phase, nothing gets
connected to the center point except the ground.
This gives the best of both worlds. Devices draw less current thus more
safety there. Touching any hot by a grounded person will only give you
a 120V shock, unless touching 3 phase where you would get zapped with 139V.
You'd need to manage to touch 2 hots at once to get zapped with 240V.
GFCIs could be used everywhere. No 4 wire 240V circuits, 2 hots+ground
everywhere. 3 phase has 3 hots+ground.
The big drawback is all light switches need to be double pole, and 3 way
switch circuits get "interesting".
There are some wiring systems that somehow reseble your ideas:
230V between phases and no neutralin the supply (also called 230V
delta). Houses are then fed two phase wires, neither of which is
necessarily anywhere near earth potential. This is used in at least in
Norway in some locations. Light switches are double pole here.
Some places in Belgium three phase 220 across the phases (= 127 phase
to earth/neutral, 230V Y output on transformer) is used on older
domestic dwellings (new installations are 400/230V 3 phase, neutral,
earth). For this reason all Belgian fuseboards (whether actual fuses
or circuit breakers) protect both current carrying wires irrespective
of supply type.
Tomi Engdahl (http://www.iki.fi/then /)
Take a look at my electronics web links and documents at
Seriously flawed understanding.
pi * r^2 * h is not the same as pi * 2 * r * h
You talked about half the copper in a wire -
that's the volume (pi*r^2*h) of a cylinder
In your reply, you erroneously equate that to
surface area which is pi*2*r*h for a cylinder.
Two 14Ga 1.25" long leads helically twisted together at 3 twists per
inch will be far better "contacted". than two 1.25" 16Ga leads at 3
twists per inch. Anybody with a simple CAD package can draw that
Also, his remark that the difference is nil, will ONLY apply to a
working circuit. Since the safety concern revolves around circuit
failure mode conditions, the current density would be much higher.
Will not happen for YEARS.
Like it or not, today most money is made in "clean" pursuits.
In Virginia, for example, there is pressure to shut down the commercial
fishing industry (what's left of it) so that "sport fish" have more to eat.
There is more money in tourists than "real" farming. There is more money
in pandering to the "sport" fishermen than the folks who fish and process
the fish to support their families.
It would take another "Great Depression" with folks jumping out of windows
to change all of that.
The price of copper has just about tripled during the last year
according to infomine.com Copper has gone from about $1.30 to $3.15 a
pound. Take a look at this chart.
(According to copper.org it takes about 400 pounds of copper to wire a
Additionally, the world's second largest deposit of copper, the Pebble
deposit, has been discovered in Alaska but the owners cannot get a
permit to develop this mine because the environmentalists and fishermen
are worried about the effects on the fishing industry near Anchorage.
(link: http://www.northerndynastyminerals.com/ndm/Home.asp Add to this
the cost of doing business in the US. The environmental, safety, and
labor laws triple the cost of production over many other countries.
On 18 Jun 2006 13:52:57 -0700, email@example.com wrote:
Here in Oregon, there have been several cases of Meth Addicts pulling
all the romex out of partially unfinished houses to sell for scrap.
The homeowner ( or the insurance company) is out for $12,000 or so and
the electrical system has to be rebuilt from scratch.
I'm told the power companies are nevous about idiots who get inside
their substations and start hacking away at the ground system ( or
worse, live copper conductors).
I had a friend once who used to install radio transmitters all around
the world. He said he once worked in an African country where the
natives kept tearing down the power lines to the transmitter site to
make trinkets. It sounds like its getting that bad in the USA in
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