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Vortex4 Vortex4 is offline
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Default Moving a Consumer Unit. Cable extension "best practice" question. [PING Andy Gabriel]


"Andrew Gabriel" wrote in message
...
In article ,
"Vortex4" writes:
Hi,

I need to move 6 circuits from an old CU (which will be removed) to a
new
one (which is already installed).

2 x ring main (32 Amp)
1 x Simple spur (15 Amp, to boiler and controls)
3 x lighting (5 Amp)

The problem is that I will need to extend the existing cabling by about 2
feet to the new CU.

I intend to use IMO DIN components / IP66 enclosure which I will install
at
the location of the (old) CU.

My question arises from this pic I found (posted by Andy)
http://www.cucumber.demon.co.uk/cu1.jpg and concerns the ring main
circuits:

QUESTION

Given that the CU and the DIN rail will be separated, should I extend the
ring circuits using 2 x 2.5mm T&E cables so they meet at the new CU?
Or
is it valid to run single 4.0mm T&E from junction box to new CU
(essentially
as in the picture)?


You can use 4.0mm T&E (although I actually used 6mm, and that's going
to be better where you might have cable grouping, and it's more common).

One concern might be the single earth, whereas a ring has two separate
earth routes. However, what's not so obvious in the picture is that
all the DIN rail earth terminals also connect to the DIN rail, so
actually there are 4 paralleled earth connections from the DIN rail
back to the main earthing terminal. Were it not for this, I would
say that if you are using a single 4mm or 6mm T&E branch to a ring
circuit, I would add a second earth connection in parallel with the
integral earth in the T&E for redundancy.

The other suggestion I would make -- use one size larger DIN rail
terminal than you might think you need, particularly where multiple
conductors are being connected. When a DIN terminal says 2.5mm (or
whatever), it really means it - there's no spare space in the
terminal at all.

Also, it would have been easier if I'd used a larger box for making
the cable connections at the top.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]


Thanks for the input Andrew,

I had not considered the earth redundancy via the DIN rail.

D