"N Cook" wrote in message
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Tam/WB2TT wrote in message
. ..
"N Cook" wrote in message
...
This is someone's graphic of internal wiring of a UK line connector
http://web.onetel.net.uk/~uncletony/...mains-plug.jpg
note the screw down, into captive hollows, for the bared leads , also
the
cord grip and also the internal fuse.
This week I had to wire up a USA mains connector like this one
http://www.maplin.co.uk/images/Full/hl19v.jpg
I could not find an internal pic or graphic but it reminded me of the
internal wiring of UK plugs of 50 years ago, before ROSPA and BS got
involved - , wrap around screw terminals that can easily shed a loose
wire
filament,
I have never seen a house here in the US wired with stranded wire, except
for one built in 1906. Generally #14 solid copper. BTW the 3 wire UK plug
reminds me of what is used on a clothes dryer or stove here. Would you
actually use one of these on a lamp?
Tam
both of them, live and neutral surprisingly close together and
what I find very odd , no cord grip/anchor and no fuse.
We have no choice in the matter, by law, we can use 1,2 or 3 amp fuses
inside these plugs but thats the only choice
The USA cannot have the equivalent of RoSPA (Royal Society for the
Prevention of Accidents), AFAICS none of the USA ones have child
preventers
on them unless the mouldings on the wall outlets preclude that eventuality
of small fiongers touching both pins.
The other notable difference is the insulated pins that have been
necessary
refinement, again by law, for 20 years or so
You can just see the orange plastic bits extending up the brass pins on
the
first pic on this wiki and the black bits on the one lower down on
http://en.wikipedia.org/wiki/BS_1363
...
The phase and neutral pins on modern plugs have insulated bases to prevent
finger contact with pins and also to stop metal sheets (for example,
fallen
blind slats) from becoming live if lodged between the wall and a partly
pulled out plug. A downside to this prong insulation is that it may
contribute to damaged sockets not making good contact with the prongs,
which
may even melt the latter. No such problems exist with healthy sockets.
...
as an aside someone told me that per million houses there are more house
fires in the USA due to wiring faults than any other country, partly due
to
a lot of timber construction and partly due to the higher current for a
given KW of power transfered - is that the case?
All heavy loads are connected across 240 Volts. 120 is basically used for
things that can be moved from room to room. There seem to be two main causes
for electrical fires in the US. One the improper use of extension cords; for
example, a 10 foot length of 5 amp wire with a refrigerator and microwave
plugged in at the far end. This comes about because older houses and
apartments tend to have an insufficient number of wall outlets. Two, there
was some problem with houses built about 30 years ago that uses aluminum
wire; these require special connection methods. When a home owner replaces a
switch or an outlet with a standard device, you have problems. Most home
owners here tend to do their own electrical repairs.
I think there is an inherent safety factor in a system where neither side of
a 240V circuit is more than 120 V above earth potential. Never heard of a
person being electrocuted who was not standing, or otherwise submerged, in
water. This costs money. For instance the wiring to an electric clothes
dryer will have two 20 Amp hot wires, a 20 Amp neutral wire (from center tap
of transformer), and a 20 amp earth ground wire connected to a cold water
pipe or ground rod. In some localities, the neutral and ground wires can be
tied together at the appliance. I think the only reason for the heavy
neutral and ground wires is to make sure the circuit breaker trip in case of
a short. As recently as about 20 years ago, a much smaller earth ground wire
was used.
The electric use meter must be more expensive than an unbalanced single
phase one.
Tam