On 26/11/2013 20:49, Bill wrote:
In message , John
Rumm writes
Sometimes its a case of needing to carefully identify the wires
already there, disconnect everything and start again neatly dressing
(and extending if required) the wires...


Identifying and labelling is one of the things that I need to do, there
are 2 very large bundles at the moment, 1 heading upwards and 1 downwards,.


Adding a RCBO to an already full box can be difficult. (when I
replaced my CUs in similar circumstance - I did not spend that much
time making it particularly pretty, which I came to regret later when
adding an RCBO. Fortunately it went in, but not in the position I
would have chosen normally).

I had a look and I might, only might, manage to squeeze 1 in! So a
definite tidy up is needed.



Yes I could crimp leads and use one box of terminals, I use crimps
frequently for lower voltages and I'm quite happy with them, but for
some reason just don't fancy the idea here.

You could also use Wago terminals - but to be fair crimps are smaller
and slimmer when space is important.

Of course the short days and long dark nights are just the right time of
year to do this, I'm not known for my forward planning :-)

Head torch, spare batts, and battery power tools that are *charged* ;-)

I can actually cheat a bit here, I have an annexe that will still have
power, so an extension lead and lamp could be used. Still not as good
as real daylight though. Also if I give up for the night I can adjourn
to the annexe!!

Where the feed from the meter comes into the main house I put a Henley
block that then goes to 2 100A fused switches, 1 for the main house and
1 for the annexe. I must have been forward planning! :-)



So, the one technical question that I have. I would imagine that 4mm
singles should be adequate to link the DIN terminals to the RCBOs,
certainly OK for lighting, but should I be thinking of 6mm for some of
the others?

IME RCBOs will come with the required fly lead to connect back to the
neutral bus bar.

They do, I was asking in regard to the tails from the separate DIN
terminals, if I went down that route.

Ah, yes I see what you mean. In that situation then either use the same
or greater CSA as used for the circuit wires you are extending. In the
case of a ring, you ought to either extend both ends, or bring them in
on a thicker single wire which is man enough for the nominal current for
the protective device in question.

So arguably with a ring with a B32 MCB that has two 2.5mm^2 ends, you
would mathematically arrive at 5mm^2 (hence 6mm^2 in practice), however
a 4mm^2 would be acceptable since we know that it can take the full 32A
load.

--
Cheers,

John.

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