Date   : Wed, 02 Sep 2009 03:37:55 +0200
From   : rick@... (Rick Murray)
Subject: Leccy @ Acorn World '09

David Hunt wrote:

> the socket ring main cable was rated for 45A continuous with a 32A
 > breaker and a 10mA RCD, well within the 90A continuous load the cable
 > was rated to.

The concept of a "ring main" causes great distress to the French.

Many ex-pats who do their own wiring (naughty naughty) think the French 
regs are one fuse->one wire->one socket.
Not entirely correct, it's one breaker to one wire to up to three 
sockets. Depending on purpose. I guess breakers are cheap over here, a 
modern installation would have many.

This is probably a reaction to "old" wiring. For example we have little 
screw-in wire fuses in the light switches (!) but most plugs are 
unfused. There is a master fusebox, which contains four fuses but this 
is some ridiculously high rating between "us" and the incoming power. 
Stupidly the neutral line is fused. Depending on earth flow and other 
nonsense, if this fuse goes (old age being the most likely culprit), the 
mains in the older part of the house will hike itself up to around 400V. 
II know this for a fact as I considered pulling that fuse to cut the 
power in one easy go, and then measured what happened next (luckily all 
that was 'on' were a few lights - the energy saving one died and the 75W 
normal turned into a halogen floodlight!).

I oughta put a photo of the old wiring someplace. Until then, imagine a 
metal box with four big thumbscrews, plus a copper lug for the earth 
connections, what few there are. Now grab a big wodge of spaghetti and 
throw it. Now imagine that spaghetti is wiring. The old braided 
rubber-insulted stuff. That's right. Scary image, isn't it? :-)


 > it doesn't take many appliances with these characteristics to overload a
 > trip. I agree. it's a pain having to go around and turn off everything
 > and then perform a selective soft-start.

Doesn't this imply that such a setup is non-recoverable from a power 
failure? I mean, if you have a blackout and the trips go upon power 
being restored... won't be good for stuff in your freezer, or maybe a 
server, whatever.


Best wishes,

Rick.

-- 
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