In message , John
Rumm writes:
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That was true. The design has evolved since however. As luck would
have it, it turns out that ring circuits are very well suited to
modern usage patterns.
Would you care to elaborate on that? (Not disagreeing: just
curious.)
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The design evolving, or being well suited to modern usage?

Sorry, I meant the latter.
[]
In terms of suitability for current use; modern use (outside of the
kitchen anyway) is typified by large numbers of lowish power devices
scattered about. A few higher power items used intermittently. Its what
is known as a highly diverse load. Which is a statistical way of
looking at it and saying that although the peak load may massively
exceed the circuit capacity, reality will mean that you never use the
peak capacity (i.e. every appliance on at once).

(Bit like traffic capacity on telecomm.s systems - Erlangs and the
like.) Yes, I would say the vast majority (outside the kitchen/utility
room, as you say) of consumption in the modern home probably comes to
well under a kW on any one circuit most of the time, and in fact - I
hadn't thought of this until now - the power consumed in the power
circuit will be comparable to that in the lighting circuit. (At least
while there are lots of filament bulbs left.) Few people use _any_
high-current appliances apart from cooking and washing; the most is
likely to be power tools _used for a short time_, and the _occasional_
use of a fan heater or similar. (With exceptions such as when drying out
after a flood, and the like - which is likely to require alternative
supplies anyway as the house ones would be compromised.)

Hence what you need are lots of socket outlets, spread over a wide
area, with enough current capacity to supply the low level background
mix of things, plus a handful of larger intermittent loads dotted

(To merge with another thread - things that certainly don't need BS1363
plugs. Though if the gentleman with the oriental-sounding name gets his
folding one off the ground ... though they'll still be bulky.)

about. A modern ring can cover 100m^2 of floor area, and will
frequently have 20 or more double sockets. It can feed a sustained load
of 7kW, or peak well above that for short durations without sustaining
any cable damage or tripping its protective device. Its also easier to
wire (thinner cable) than an equivalent radial, and handles the most
common failure modes of a circuit "better" than a radial.

I think the "easier to wire (thinner cable)" is probably one of the best
things in its favour.

Care still needs to be exercised to choose the right circuit though for
the application, and to plan the layout. No point installing a ring for
example if you are powering a large number of long term fixed loads
that will use 90% of the circuit capacity all the time, or if you are
going to end up with most of the high current appliances all lumped
right at one end of it.

Exactly. It is the "one size fits all" aspect that bugs me - enshrined
in regulations that more or less insist on a ring for any substantial
new build.


--
J. P. Gilliver. UMRA: 1960/1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf
** http://www.soft255.demon.co.uk/G6JPG-PC/JPGminPC.htm for ludicrously
outdated thoughts on PCs. **

"Forget computers; it's hard enough getting humans to pass the Turing test."
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