In article ,
Mike Barnes writes:
The subject of British ring mains came up in another group
(alt.usage.english). When it was said that nobody really knew the
history, one contributor came up with this explanation, which I
reproduce here for your entertainment.

Well, there's a very tiny bit of truth, corrupted by gross
inaccuracies which could be a case of chinese whispers - gradual
corruption each time the story was retold.

Firstly, a "Ring Main" applies to electricity distribution in the
street to premises, and at a higher level, distribution between
areas. It is commonly incorrectly applied to the 30A/32A final
ring circuit in the home, which I assume is what was meant here.

The earlier wiring schemes used radial circuits with a 15A
socket on each radial circuit, back to a fuse in the fuse box.
Most rooms only had one 15A socket, so this was not too onerous.
Sometimes a 5A socket was also provided for light loads.
As electrical appliances grow in popularity, the idea of only
one socket in each room rapidly became unviable, but also the
idea of routing loads of 15A circuits back to the fusebox was
also not viable. It was recognised that you probably didn't need
more than 15A in a room (the room would get uncomfortably hot
if you did), but you might want to draw that load from anywhere
in the room, and indeed split it over multiple outlets. Thus
was born the (now obvious) idea of multiple socket outlets.

This was considered for some years pre-WWII, but implementation
came at the end of WWII when there was a shortage of copper.
This influenced the design which became the final ring circuit
we know today. The idea was to provide unlimited socket outlets,
but to recognise that only a certain amount of power was required
over any floor area, and not the maximum which each socket could
provide all at once. The design also allowed easy conversion from
15A radials to 30A ring circuit by reusing the same wire (although
that probably wasn't as common as had been envisaged). The design
included a move to a single socket type to handle everything, from
the horibble mixture of earlier 15A, 5A, 2A, 2- and 3-pin sockets
to make life much simpler.

I think it's a design which has lasted and worked very well.
There have been very few later corrections required (upping the
earth conductor size is the only one I can think of, apart from
a few safety improvements to the 13A plug). As such, the
opportunity to chuck out what we had before and start again
was a real benfit, and it was probably done at the last moment
it could have been before proliferation would have made any such
change impossible.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]