Having finally decided what we're going to do with the downstairs area,
we're going to have to move the consumer unit by about 4 foot. I wish
I'd thought of this scenario when rewiring :-(

Some of the circuits I'll be able to simply replace the last leg of
cable (from CU back to first socket), while others I'll have to extend
the cables.

I've read all previous threads on this, but haven't come across an
answer to this query:

Where I have a ring, with two 2.5mm cables going to the CU, instead of
extending each of the two 2.5mm cables, can I just join them up and
connect to the CU using a single 6mm cable? Anyone see a problem with this?

Just to make sure I'm being clear, the two ends of the ring, currently
both ending up in the CU, would instead both go into a 30A junction box.
Then a 6mm cable would leave the juntion box and connect to the CU.

TIA

--
Grunff

"Grunff" wrote in message
...
Having finally decided what we're going to do with the downstairs area,
we're going to have to move the consumer unit by about 4 foot. I wish
I'd thought of this scenario when rewiring :-(

Some of the circuits I'll be able to simply replace the last leg of
cable (from CU back to first socket), while others I'll have to extend
the cables.

I've read all previous threads on this, but haven't come across an
answer to this query:

Where I have a ring, with two 2.5mm cables going to the CU, instead of
extending each of the two 2.5mm cables, can I just join them up and
connect to the CU using a single 6mm cable? Anyone see a problem with
this?

Just to make sure I'm being clear, the two ends of the ring, currently
both ending up in the CU, would instead both go into a 30A junction box.
Then a 6mm cable would leave the juntion box and connect to the CU.


Where is this junction box placed. In theory you are simply copying the
arrangement normally in the CU but in a CU one usually tightens up all the
screws when you are in there wheras this junction box will probably never
get touched again. Screws unfortunately do come loose.

G&M wrote:

Where is this junction box placed. In theory you are simply copying the
arrangement normally in the CU but in a CU one usually tightens up all the
screws when you are in there wheras this junction box will probably never
get touched again. Screws unfortunately do come loose.

Well, that's true - but it's also true of screws in sockets and light
fittings, which might get tightened once every 20 years or so!

The junction boxes will be going under the floorboards, so accessible
but not very easily. I believe that use of junction boxes in this
situation is compliant with the regs (screw terminals are ok as long as
they are accessible).

--
Grunff

"Grunff" wrote in message
...
G&M wrote:

Where is this junction box placed. In theory you are simply copying the
arrangement normally in the CU but in a CU one usually tightens up all
the
screws when you are in there wheras this junction box will probably
never
get touched again. Screws unfortunately do come loose.

Well, that's true - but it's also true of screws in sockets and light
fittings, which might get tightened once every 20 years or so!

Agreed - and I expect a large number of sockets in older installations
aren't part of a ring anymore on at least one conductor. It's more that
when something goes wrong with your scheme, there's likely to be a very
confused electrician wondering what's gone wrong. Of course a message or
diagram attached to the inside of the CU might be helpful


The junction boxes will be going under the floorboards, so accessible
but not very easily. I believe that use of junction boxes in this
situation is compliant with the regs (screw terminals are ok as long as
they are accessible).

Well that's slightly more inaccessable than I stick to but may be OK. What
do others think ?

In article ,
Grunff writes:
Having finally decided what we're going to do with the downstairs area,
we're going to have to move the consumer unit by about 4 foot. I wish
I'd thought of this scenario when rewiring :-(

Some of the circuits I'll be able to simply replace the last leg of
cable (from CU back to first socket), while others I'll have to extend
the cables.

I've read all previous threads on this, but haven't come across an
answer to this query:

Where I have a ring, with two 2.5mm cables going to the CU, instead of
extending each of the two 2.5mm cables, can I just join them up and
connect to the CU using a single 6mm cable? Anyone see a problem with this?

Just to make sure I'm being clear, the two ends of the ring, currently
both ending up in the CU, would instead both go into a 30A junction box.
Then a 6mm cable would leave the juntion box and connect to the CU.

I think this is fine.
However, I would only connect one of the earths to the 6mm cable's earth.
I would run the other in a separate green/yellow single to the earthing
terminal in the CU so there is no single failure point for the CPC.
(It's good practice to wire the two ends of CPC in a ring to different
earthing terminals too, so one loose screw won't lose you all the ring's
earthing.)

--
Andrew Gabriel

Andrew Gabriel wrote:

I think this is fine.
However, I would only connect one of the earths to the 6mm cable's earth.
I would run the other in a separate green/yellow single to the earthing
terminal in the CU so there is no single failure point for the CPC.

Ok, that seems like a good idea. Thanks.


(It's good practice to wire the two ends of CPC in a ring to different
earthing terminals too, so one loose screw won't lose you all the ring's
earthing.)

Yup, I've done this throughout.

--
Grunff

On Mon, 03 May 2004 21:06:10 +0100, in uk.d-i-y Grunff
strung together this:

Just to make sure I'm being clear, the two ends of the ring, currently
both ending up in the CU, would instead both go into a 30A junction box.
Then a 6mm cable would leave the juntion box and connect to the CU.

I've done it many times before, not quite sure if it's strictly to the
regs but the consensus of the group last time this was raised was yes,
go ahead it's fine. And everyone I've worked with!
--

SJW
A.C.S. Ltd.

"Lurch" wrote in message
...
On Mon, 03 May 2004 21:06:10 +0100, in uk.d-i-y Grunff
strung together this:

Just to make sure I'm being clear, the two ends of the ring, currently
both ending up in the CU, would instead both go into a 30A junction box.
Then a 6mm cable would leave the juntion box and connect to the CU.

I've done it many times before, not quite sure if it's strictly to the
regs but the consensus of the group last time this was raised was yes,
go ahead it's fine. And everyone I've worked with!


SJW
A.C.S. Ltd.

This sounds OK, but try to get a 45amp junction box and give yourself a bit
more of a safety margin. You should also find it bit easier to get the
cables into it.


---
http://www.basecuritysystems.no-ip.com

Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.673 / Virus Database: 435 - Release Date: 01/05/04

BigWallop wrote:

This sounds OK, but try to get a 45amp junction box and give yourself a bit
more of a safety margin. You should also find it bit easier to get the
cables into it.

On the topic of junction boxes, anyone recommend a *good* make? The ones
from Screwfix (and my local CEF, and B&Q, and Wickes) are very poor. I
could carry on buying them from different suppliers until I find a good
one, but a recommendation would be nice.

--
Grunff

Grunff wrote:
Andrew Gabriel wrote:

(It's good practice to wire the two ends of CPC in a ring to different
earthing terminals too, so one loose screw won't lose you all the ring's
earthing.)

Yup, I've done this throughout.

On the other hand it means all the numbering on the earth bar is
wrong.

--
Chris Green

wrote:

On the other hand it means all the numbering on the earth bar is
wrong.

There's numbering on the earth bar?!? ;-)

--
Grunff

"Grunff" wrote in message
...
Having finally decided what we're going to do with the downstairs area,
we're going to have to move the consumer unit by about 4 foot. I wish
I'd thought of this scenario when rewiring :-(

Some of the circuits I'll be able to simply replace the last leg of
cable (from CU back to first socket), while others I'll have to extend
the cables.

I've read all previous threads on this, but haven't come across an
answer to this query:

Where I have a ring, with two 2.5mm cables going to the CU, instead of
extending each of the two 2.5mm cables, can I just join them up and
connect to the CU using a single 6mm cable? Anyone see a problem with
this?

Just to make sure I'm being clear, the two ends of the ring, currently
both ending up in the CU, would instead both go into a 30A junction box.
Then a 6mm cable would leave the juntion box and connect to the CU.

TIA

--
Grunff

Grunff,

I'm sure it'll work fine but I'm also sure it'll confuse people in the
future. If you have to put in one junction box to do it 'your way' why not
put one in each leg so inside the C.U. they are conventional and seperable
if anyone has to do a loop impedance test.

Andrew Mawson

Just to make sure I'm being clear, the two ends of the ring, currently
both ending up in the CU, would instead both go into a 30A junction box.
Then a 6mm cable would leave the juntion box and connect to the CU.

I'd crimp (and solder) two 2.5mm runs. This way, you know the connections
will still be made in twenty years time, when the junction box is under your
new stone/laminate/hardwood T&G floor.

Christian.

Christian McArdle wrote:

I'd crimp (and solder) two 2.5mm runs. This way, you know the connections
will still be made in twenty years time, when the junction box is under your
new stone/laminate/hardwood T&G floor.


How would you house your made connection(s)?

--
Grunff

How would you house your made connection(s)?

Heatshrink tubing then insulation tape.

Christian.

Christian McArdle wrote:
How would you house your made connection(s)?


Heatshrink tubing then insulation tape.

Not box up in any way?

--
Grunff

Heatshrink tubing then insulation tape.

Not box up in any way?

I wouldn't bother, unless there is a specific reason to do so, such as the
likelihood of mechnical damage.

Christian.

On 4 May 2004 08:41:11 GMT, in uk.d-i-y strung
together this:

On the other hand it means all the numbering on the earth bar is
wrong.

Renumber it then.
--

SJW
A.C.S. Ltd.

On Tue, 04 May 2004 09:24:53 +0100, in uk.d-i-y Grunff
strung together this:

BigWallop wrote:

This sounds OK, but try to get a 45amp junction box and give yourself a bit
more of a safety margin. You should also find it bit easier to get the
cables into it.

On the topic of junction boxes, anyone recommend a *good* make? The ones
from Screwfix (and my local CEF, and B&Q, and Wickes) are very poor. I
could carry on buying them from different suppliers until I find a good
one, but a recommendation would be nice.

The BG ones are pretty roomy, you'll easily get 2x2.5mm and a 6mm in
them. They're Senates own brand, Sector or some other wholesalers
stock them under the BG label.
--

SJW
A.C.S. Ltd.

Grunff wrote:
wrote:

On the other hand it means all the numbering on the earth bar is
wrong.

There's numbering on the earth bar?!? ;-)

On all three of the consumer units I've installed in the past couple
of years the neutral bus bar and the earth bus bar both had numbers.
I thus matched up the numbers used with the MCB positions for each
cable as that seemed to be what was intended.

That's a Crabtree, a Denmans own brand and a n other whose brand I
can't remember.

--
Chris Green

wrote:
There's numbering on the earth bar?!? ;-)


On all three of the consumer units I've installed in the past couple
of years the neutral bus bar and the earth bus bar both had numbers.
I thus matched up the numbers used with the MCB positions for each
cable as that seemed to be what was intended.

That's a Crabtree, a Denmans own brand and a n other whose brand I
can't remember.


I know - see the smilie? I just meant that because I wanted to separate
the earths, I ignored the numbering on the earth bar. I matched the
numbers on the neutrals with the MCB positions. That'll confuse the next
guy!

--
Grunff

"Grunff" wrote in message
...
wrote:

On the other hand it means all the numbering on the earth bar is
wrong.

There's numbering on the earth bar?!? ;-)

Yep - only I didn't notice it was back to front form the line and neutral
until I had finished :-)

In message ,
(Lurch) wrote:

On Tue, 04 May 2004 09:24:53 +0100, in uk.d-i-y Grunff
strung together this:

BigWallop wrote:

This sounds OK, but try to get a 45amp junction box and give yourself a bit
more of a safety margin. You should also find it bit easier to get the
cables into it.

On the topic of junction boxes, anyone recommend a *good* make? The ones
from Screwfix (and my local CEF, and B&Q, and Wickes) are very poor. I
could carry on buying them from different suppliers until I find a good
one, but a recommendation would be nice.

The BG ones are pretty roomy, you'll easily get 2x2.5mm and a 6mm in
them. They're Senates own brand, Sector or some other wholesalers
stock them under the BG label.

My own problem with the Screwfix and B&Q ones isn't usually space
(though I do tend to use 20A 4-terminal boxes on lighting circuits
rather than the 5A variety), it's the design of the terminal itself.
Particularly on the 30A 3-t jobbies the U-shaped brass insert into a
plastic moulding looks good, but if you get a wire in slightly skewiff
or apply slightly too much pressure on the grub screw it is very easy to
crack the plastic leading to a loose connection and hence a scrap JB.

I'd appreciate any ideas too, though of course the Screwfix boxes are so
cheap it hardly matters if you lose one or two every now and again.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... FANATIC: one enthusastic about something you don't care about.

Martin Angove wrote:

My own problem with the Screwfix and B&Q ones isn't usually space
(though I do tend to use 20A 4-terminal boxes on lighting circuits
rather than the 5A variety), it's the design of the terminal itself.
Particularly on the 30A 3-t jobbies the U-shaped brass insert into a
plastic moulding looks good, but if you get a wire in slightly skewiff
or apply slightly too much pressure on the grub screw it is very easy to
crack the plastic leading to a loose connection and hence a scrap JB.

Yup, had that many times.


I'd appreciate any ideas too, though of course the Screwfix boxes are so
cheap it hardly matters if you lose one or two every now and again.

But what would worry me is using a junction that's this marginal in a
concealed location.

I have to say, I still really like terminal blocks (chock blocks). For
this type of application, the 30A ceramic ones from SF are great. They
have the added advantage of having two screws per connection, so if you
overlap the cables, there's very little chance of failure. You just have
to come up with a good enclosure.

--
Grunff

In message , Christian
McArdle writes
Heatshrink tubing then insulation tape.

Not box up in any way?

I wouldn't bother, unless there is a specific reason to do so, such as the
likelihood of mechnical damage.

And if you did want to enclose them, plenty of adaptable boxes a round.

--
Chris French, Leeds