In message ws.net,
":::Jerry::::" wrote:
As you are "GMT not EDT" then:
Anyway, all the radials I've ever come across have only one or two
outlets per circuit, and certainly didn't cross room or floor
boundaries.
Probably the most common radials to be found in Britain are those for
showers (no sockets, obviously), lights and cookers, however we're
talking specifically about circuits supplying socket-outlets.
There are three "standard" circuits for use with BS1363 socket outlets:
"A1" is a ring topology with 30 or 32A protection wired in 2.5mm2/1.5mm2
cable. Such a ring can serve a floor area of up to 100m2.
"A2" is radial with 30 or 32A protection wired in 4mm2/2.5mm2 cable
(though it is only really rated for "clipped direct" and many people
advocate the use of 6mm2 cable instead). This type of radial can serve
up to 75m2.
"A3" is radial with 20A protection (though possibly more often found
with 15/16A) wired in 2.5/1.5 cable and serving up to 50m2.
The IEE On Site Guide says "A ring or radial circuit, with spurs if any,
feeds permanently connected equipment and an unlimited number of
socket-outlets and fused connection units." (Appx 8)
Given that an average Valleys terraced house will have a floor area of
70 to 80m2 you can see that it is perfectly possible to wire the entire
house with one ring circuit, and it may even be possible to wire it with
one 30A radial. It will certainly be possible to wire it with two
radials of either rating (cable length aside). You can see that there
will be many more than your "one or two outlets per circuit" and that
the circuit will of necessity cross both room and floor boundaries.
Indeed, for a house shaped like a terrace (i.e. long and narrow), a
radial may be the most economical use of cable.
Therefore, from a discrimination point of view, there is absolutely no
advantage at all from running radials.
If we follow your idea of radials feeding just a few outlets - let's be
charitable and say one radial per "room" - then you begin to escalate
the cost of the system enormously. My house is unusual in that I have
three ring (East, West, Kitchen) and two radial circuits
(utility/outside, fridge). Five sockets circuits is a lot for a house
with a floor area of some 80m2 (three bed semi). With the "one radial
per room" idea though, I'd need even more!
Three bedrooms
One for hall/landing ("office" area on landing)
living room
kitchen
dining room
utility
outside
fridge
Makes a total of ten circuits; double the number. I have a 12-way board
which, at the moment, has a few spare ways. With the new regime that
board would be over-full:
10 sockets radials
2 lights
1 cooker
1 heating radial
makes 14. Also the utility/outside circuit I have installed is run from
an RCBO rather than from the RCD which commonly feeds the rings. This
RCBO takes two slots in the board so now I need 15 ways; whatever, it
means a bigger board. A 12-way board kit is available from Screwfix for
as little as £60. Bigger boards are a lot more expensive as they are
less common.
And then what about the spare ways I currently have? One of them is
earmarked for a supply to the shed I'm planning. One of them might be
used for a third lighting circuit. Perhaps the best way would be with
two 10 or 11 way boards, one exclusively for the sockets radials and one
for everything else? Never mind the cost, what's the wife going to say?
Even after all that, you *still* have multiple outlets per circuit, and
hence unfused connections (which I think were the original argument) are
still a big problem. In total we have the equivalent of 31 double
sockets in the house. This is an average of three and a bit per circuit
to the "one radial per room" plan, though two of the radials only
actually serve one double each.
I wasn't going to add any more to this thread, but I'm intrigued how you
can be such a radial fan when it doesn't (in real life) solve any
problems.
Hwyl!
M.
--
Martin Angove:
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