On 28/05/2015 10:26, Dave Plowman (News) wrote:
In article ,
John Rumm wrote:
On 28/05/2015 00:45, Dave Plowman (News) wrote:
In article ,
GB wrote:
Tell me, dennis, just why would there be any 'movement' in any part of a
properly installed final ring circuit?


Why do faults occur in electrical circuits if there is no movement?

There must be thermal expansion and contraction, surely?

As there is with any metal. But you don't expect the copper pipes in your
central heating to fail,

You may not expect it, and indeed I did not, but:

http://wiki.diyfaq.org.uk/index.php?...e_rubbing_pipe

so why expect wiring to do so?

That I expect more - however its only an issue on circuits that run at
near full load for extended periods IME.

And the requirements of a final circuit ring is that it isn't. Devices
which take a high extended load - like say space heating or water heating
- are covered separately.

It's the beauty of a ring. It's eminently suitable for the sort of actual
use it gets in domestic premises. Lots of relatively low current devices
used intermittently. And a large number of outlets to avoid having
trailing cables.

The proof, as they say, is in the pudding.

Indeed - as a design it has endured because it works so well with modern
usage patterns.


--
Cheers,

John.

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