Is it allowed to extend an old circuit using black and red wiring with new blue and brown. (the grey cable, not the rubbery black stuff)

Isn't the CPC wire size bigger in blue and brown?

I have several circuits (sockets and lights) running from a 'submain' fusebox,
I'd like to use them but powering each from a separate MCB and blue and brown cable coming from the consumer units at the other end of the house.

Thus all fuses and trips will be in one location.

But is it allowed to mix different cables in one circuit?
And how would I calculate the maximum size of MCB per circuit?

And for lighting circuits can I run the main power line in 1.5mm and then spurs to individual lights in 1mm squared?

Eventually I want to do full paperwork and testing and try to get it all approved by the council under building regs.

George

On Friday, 29 December 2017 14:01:13 UTC, George Miles wrote:
Is it allowed to extend an old circuit using black and red wiring with new
blue and brown. (the grey cable, not the rubbery black stuff)

Yes.

Isn't the CPC wire size bigger in blue and brown?

No.

But is it allowed to mix different cables in one circuit?

Yes

And how would I calculate the maximum size of MCB per circuit?

Maximum demand after diversity, but if you're not an electrician you probably don't need to go beyond the standard circuits:

6A lighting on 1 or 1.5mm
20A radial sockets on 2.5mm
32A ring sockets on 2.5mm
32A radial sockets on 4 mm

And for lighting circuits can I run the main power line in 1.5mm and
then spurs to individual lights in 1mm squared?

No, cable should be the same size throughout the circuit. 1mm is actually adequate for most 6A lighting circuits in houses where the cable length isn't too long.

Owain

wrote:

George Miles wrote:

Is it allowed to extend an old circuit using black and red wiring with new
blue and brown.

Yes.

But you should put a warning sticker on your CU(s)

https://www.labelsonline.co.uk/electrical-labels/bs7671-cable-colour-harmonisation-labels

On Friday, 29 December 2017 14:01:13 UTC, George Miles wrote:
Is it allowed to extend an old circuit using black and red wiring with new blue and brown. (the grey cable, not the rubbery black stuff)

of course

Isn't the CPC wire size bigger in blue and brown?

sometimes. You're not required to upgrade though

I have several circuits (sockets and lights) running from a 'submain' fusebox,
I'd like to use them but powering each from a separate MCB and blue and brown cable coming from the consumer units at the other end of the house.

Thus all fuses and trips will be in one location.

But is it allowed to mix different cables in one circuit?

yes

And how would I calculate the maximum size of MCB per circuit?

lighting 6A, sockets 32A ring, 20A or 32A radial depending on cable

And for lighting circuits can I run the main power line in 1.5mm and then spurs to individual lights in 1mm squared?

of course, both are fine on 6A mcb

Eventually I want to do full paperwork and testing and try to get it all approved by the council under building regs.

George


NT

On 29/12/2017 14:01, George Miles wrote:
Isn't the CPC wire size bigger in blue and brown?

It changed in about 1983-ish from 1mm to 1.5mm AFAIK, but
ARW or John Rumm will no doubt confirm this. Something
to do with guaranteeing that even a non-rcd protected
circuit would trip or blow its MCB or fuse in the
required minimum period (?40 msec).

So you'll probably be ok with an RCD/RCBO or maybe even just
an MCB, but not an old-fashioned fuse arrangement.

On 29/12/2017 14:14, wrote:
On Friday, 29 December 2017 14:01:13 UTC, George Miles wrote:
Is it allowed to extend an old circuit using black and red wiring with new
blue and brown. (the grey cable, not the rubbery black stuff)

Yes.

Isn't the CPC wire size bigger in blue and brown?

No.

With some exceptions? 2.5mm² T&E had only 1mm² CPC in the 70s

http://wiki.diyfaq.org.uk/index.php/..._Old_Electrics

But is it allowed to mix different cables in one circuit?

Yes

And how would I calculate the maximum size of MCB per circuit?

Maximum demand after diversity, but if you're not an electrician you probably don't need to go beyond the standard circuits:

6A lighting on 1 or 1.5mm
20A radial sockets on 2.5mm
32A ring sockets on 2.5mm
32A radial sockets on 4 mm

And for lighting circuits can I run the main power line in 1.5mm and
then spurs to individual lights in 1mm squared?

No, cable should be the same size throughout the circuit. 1mm is actually adequate for most 6A lighting circuits in houses where the cable length isn't too long.

Is that a "should" as in "best practice" rather than as in "must"?

I hope so as I've rewired lighting circuits using 1.5mm (for robustness
and to keep voltage drop low) but left some switch drops in 1mm where it
is in good nick, has a CPC and meets the conditions for overload etc -
just to avoid having to channel the walls. And of course noted it on the
form.


--
Robin
reply-to address is (intended to be) valid

Robin wrote:
On 29/12/2017 14:14, wrote:
On Friday, 29 December 2017 14:01:13 UTC, George MilesÂ* wrote:
Is it allowed to extend an old circuit using black and red wiring
with new
blue and brown. (the grey cable, not the rubbery black stuff)

Yes.

Isn't the CPC wire size bigger in blue and brown?

No.

With some exceptions? 2.5mm² T&E had only 1mm² CPC in the 70s

http://wiki.diyfaq.org.uk/index.php/..._Old_Electrics

But is it allowed to mix different cables in one circuit?

Yes

And how would I calculate the maximum size of MCB per circuit?

Maximum demand after diversity, but if you're not an electrician you
probably don't need to go beyond the standard circuits:

6A lighting on 1 or 1.5mm
20A radial sockets on 2.5mm
32A ring sockets on 2.5mm
32A radial sockets on 4 mm

And for lighting circuits can I run the main power line in 1.5mm and
then spurs to individual lights in 1mm squared?

No, cable should be the same size throughout the circuit. 1mm is
actually adequate for most 6A lighting circuits in houses where the
cable length isn't too long.


In Australia we can go up not down, the cable size can not be smaller
than the size at the fuse or breaker but can be bigger elsewhere .



Is that a "should" as in "best practice" rather than as in "must"?

I hope so as I've rewired lighting circuits using 1.5mm (for robustness
and to keep voltage drop low) but left some switch drops in 1mm where it
is in good nick, has a CPC and meets the conditions for overload etc -
just to avoid having to channel the walls. And of course noted it on the
form.

On 29/12/2017 14:48, Robin wrote:
On 29/12/2017 14:14, wrote:


No, cable should be the same size throughout the circuit. 1mm is
actually adequate for most 6A lighting circuits in houses where the
cable length isn't too long.

Is that a "should" as in "best practice" rather than as in "must"?

I hope so as I've rewired lighting circuits using 1.5mm (for robustness
and to keep voltage drop low) but left some switch drops in 1mm where it
is in good nick, has a CPC and meets the conditions for overload etc -
just to avoid having to channel the walls. And of course noted it on the
form.



I would say that it is neither a "should" or "must".

eg if you have a 4mm 32A radial circuit what sized cable are you allowed
to used for an unfused spur powering one single or one double socket?
(app 15 of the regs is your clue).

--
Adam

On 29/12/2017 14:43, Andrew wrote:
On 29/12/2017 14:01, George Miles wrote:
Isn't the CPC wire size bigger in blue and brown?

It changed in about 1983-ish from 1mm to 1.5mm AFAIK, but
ARW or John Rumm will no doubt confirm this. Something
to do with guaranteeing that even a non-rcd protected
circuit would trip or blow its MCB or fuse in the
required minimum period (?40 msec).

So you'll probably be ok with an RCD/RCBO or maybe even just
an MCB, but not an old-fashioned fuse arrangement.


The RCD protection will be a requirement for any new sockets and for
all T&E cables for any circuit that are buried in a wall behind plaster.

In 6 months time the regs will have changed and will require all new
domestic lighting to be RCD protected.



--
Adam

Well if its just for practical purposes I'd say there is really no problem
but if you are going to change the protection method, you might come
unstuck against the twitty regulations.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"George Miles" wrote in message
...
Is it allowed to extend an old circuit using black and red wiring with new
blue and brown. (the grey cable, not the rubbery black stuff)

Isn't the CPC wire size bigger in blue and brown?

I have several circuits (sockets and lights) running from a 'submain'
fusebox,
I'd like to use them but powering each from a separate MCB and blue and
brown cable coming from the consumer units at the other end of the house.

Thus all fuses and trips will be in one location.

But is it allowed to mix different cables in one circuit?
And how would I calculate the maximum size of MCB per circuit?

And for lighting circuits can I run the main power line in 1.5mm and then
spurs to individual lights in 1mm squared?

Eventually I want to do full paperwork and testing and try to get it all
approved by the council under building regs.

George

In article ,
George Miles wrote:
Is it allowed to extend an old circuit using black and red wiring with
new blue and brown. (the grey cable, not the rubbery black stuff)

Just who is going to stop you? If worried, ad a label to the CU saying
both standards are in use.

Isn't the CPC wire size bigger in blue and brown?

No - the CPC size changed during red and black production times. But if it
is bigger than your existing CPC, no harm.

--
*How many roads must a man travel down before he admits he is lost? *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Dave Plowman (News) wrote:
In article ,
George Miles wrote:
Is it allowed to extend an old circuit using black and red wiring with
new blue and brown. (the grey cable, not the rubbery black stuff)

Just who is going to stop you? If worried, ad a label to the CU saying
both standards are in use.

you should, ideally, put new colour sleeves over the old colours where they
become visible.

Isn't the CPC wire size bigger in blue and brown?

No - the CPC size changed during red and black production times. But if it
is bigger than your existing CPC, no harm.

--
from KT24 in Surrey, England

On 29/12/2017 15:28, ARW wrote:
On 29/12/2017 14:48, Robin wrote:
On 29/12/2017 14:14, wrote:


No, cable should be the same size throughout the circuit. 1mm is
actually adequate for most 6A lighting circuits in houses where the
cable length isn't too long.

Is that a "should" as in "best practice" rather than as in "must"?

I hope so as I've rewired lighting circuits using 1.5mm (for
robustness and to keep voltage drop low) but left some switch drops in
1mm where it is in good nick, has a CPC and meets the conditions for
overload etc - just to avoid having to channel the walls. And of
course noted it on the form.



I would say that it is neither a "should" or "must".

eg if you have a 4mm 32A radial circuit what sized cable are you allowed
to used for an unfused spur powering one single or one double socket?
(app 15 of the regs is your clue).


D'oh!




--
Robin
reply-to address is (intended to be) valid

On 29/12/2017 14:01, George Miles wrote:
Is it allowed to extend an old circuit using black and red wiring with new blue and brown. (the grey cable, not the rubbery black stuff)

Isn't the CPC wire size bigger in blue and brown?

I have several circuits (sockets and lights) running from a 'submain' fusebox,
I'd like to use them but powering each from a separate MCB and blue and brown cable coming from the consumer units at the other end of the house.

Thus all fuses and trips will be in one location.

But is it allowed to mix different cables in one circuit?
And how would I calculate the maximum size of MCB per circuit?

And for lighting circuits can I run the main power line in 1.5mm and then spurs to individual lights in 1mm squared?

Eventually I want to do full paperwork and testing and try to get it all approved by the council under building regs.

George

I'll be doing the same in the foreseeable future and AFAICS (and from
what others have said) there is no problem.
How do you plan to extend the cables? There seems to be a lack of
agreement on whether insulated crimps are adequate for non-accessible
areas so I was wondering about using uninsulated crimps with solder
(belt'n'braces) and suitable HS sleeving ... but insulated crimps would
be less hassle ...

In message , charles
writes
In article ,
Dave Plowman (News) wrote:
In article ,
George Miles wrote:
Is it allowed to extend an old circuit using black and red wiring with
new blue and brown. (the grey cable, not the rubbery black stuff)

Just who is going to stop you? If worried, ad a label to the CU saying
both standards are in use.

you should, ideally, put new colour sleeves over the old colours where they
become visible.

Isn't the CPC wire size bigger in blue and brown?

No - the CPC size changed during red and black production times. But if it
is bigger than your existing CPC, no harm.

I have a fair bit of red and black on the scrap pile if you don't mind
white outer insulation:-)


--
Tim Lamb

On Fri, 29 Dec 2017 15:36:40 +0000, ARW wrote:

On 29/12/2017 14:43, Andrew wrote:
On 29/12/2017 14:01, George Miles wrote:
Isn't the CPC wire size bigger in blue and brown?

It changed in about 1983-ish from 1mm to 1.5mm AFAIK, but
ARW or John Rumm will no doubt confirm this. Something
to do with guaranteeing that even a non-rcd protected
circuit would trip or blow its MCB or fuse in the
required minimum period (?40 msec).

So you'll probably be ok with an RCD/RCBO or maybe even just
an MCB, but not an old-fashioned fuse arrangement.


The RCD protection will be a requirement for any new sockets and for
all T&E cables for any circuit that are buried in a wall behind plaster.

In 6 months time the regs will have changed and will require all new
domestic lighting to be RCD protected.

To what value? My board has 100mA to lights and a few other things, then
30mA to sockets, cooker etc.
I've always liked this because if the socket is tripped the lights will
probably stay on - if I've just had a shock I'd rather not be in darkness as
well!
--
Peter.
The gods will stay away
whilst religions hold sway

On 29/12/2017 14:01, George Miles wrote:

Is it allowed to extend an old circuit using black and red wiring
with new blue and brown. (the grey cable, not the rubbery black
stuff)

Yes. (it would have to be, you can't buy red/black new now)

Once you have an installation with multiple colour codes installed, you
should have a warning label at the CU highlighting this.

Isn't the CPC wire size bigger in blue and brown?

Not with any recent cable.

Very old red/black 2.5mm^2 T&E however did have 1.00mm^2 CPC rather than
the 1.5mm^2 of more recent cables.

I have several circuits (sockets and lights) running from a 'submain'
fusebox, I'd like to use them but powering each from a separate MCB
and blue and brown cable coming from the consumer units at the other
end of the house.

Thus all fuses and trips will be in one location.

So basically remove the intermediate fusebox, and extend each of the
circuits back to the main CU?

(you could probably re-use the sub main cable for one of the circuits)

But is it allowed to mix different cables in one circuit?

Different colours? Yes.

Different cable sizes? Yes but with the proviso that the circuit
protection is set to protect the smallest cable CSAs in the circuit.
Would also be wise to have a label on the CU indicating circuits with
smaller than apparent cable sizes.

And how
would I calculate the maximum size of MCB per circuit?

If they are wired in typical sizes for the circuit type (say 2.5mm^2 T&E
for sockets and 1 or 1.5mm^2 T&E for lighting, then normal 32 and 6A
MCBs would be appropriate).

And for lighting circuits can I run the main power line in 1.5mm and
then spurs to individual lights in 1mm squared?

If you want. Any particular reason why?

Eventually I want to do full paperwork and testing and try to get it
all approved by the council under building regs.




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 29/12/2017 14:43, Andrew wrote:
On 29/12/2017 14:01, George Miles wrote:
Isn't the CPC wire size bigger in blue and brown?

It changed in about 1983-ish from 1mm to 1.5mm AFAIK, but

The rule change was a bit before than I believe, but there could well
have meant some installations still being later than that.

ARW or John Rumm will no doubt confirm this. Something
to do with guaranteeing that even a non-rcd protected
circuit would trip or blow its MCB or fuse in the
required minimum period (?40 msec).

400 ms usually (TN systems)

There is a problem on the old 1mm^2 CPC cable when you have a spur on a
ring protected in particular by a BS 3036 re-wireable fuse.

The single 1mm^2 CPC is undersized to ensure a fault to earth is cleared
(you need about 1.25mm^2 - the ring itself with 2 x 1.00mm^2 is ok, but
the spur is vulnerable)

So you'll probably be ok with an RCD/RCBO or maybe even just
an MCB, but not an old-fashioned fuse arrangement.

The "instant" trip current required for a BS3036 fuse is something like
450A compared with 160A for the B32 MCB.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 29/12/2017 17:18, wrote:
On 29/12/2017 14:01, George Miles wrote:
Is it allowed to extend an old circuit using black and red wiring with
new blue and brown. (the grey cable, not the rubbery black stuff)

Isn't the CPC wire size bigger in blue and brown?

I have several circuits (sockets and lights) running from a 'submain'
fusebox,
I'd like to use them but powering each from a separate MCB and blue
and brown cable coming from the consumer units at the other end of the
house.

Thus all fuses and trips will be in one location.

But is it allowed to mix different cables in one circuit?
And how would I calculate the maximum size of MCB per circuit?

And for lighting circuits can I run the main power line in 1.5mm and
then spurs to individual lights in 1mm squared?

Eventually I want to do full paperwork and testing and try to get it
all approved by the council under building regs.

George

I'll be doing the same in the foreseeable future and AFAICS (and from
what others have said) there is no problem.
How do you plan to extend the cables? There seems to be a lack of
agreement on whether insulated crimps are adequate for non-accessible
areas so I was wondering about using uninsulated crimps with solder
(belt'n'braces) and suitable HS sleeving ... but insulated crimps would
be less hassle ...

Good quality insulated crimps are ok. You will still need some form of
enclose for them though - so either the joint being in a box of some
sort, or the whole cable protected with heat shrink at the join.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 29/12/2017 22:26, PeterC wrote:
On Fri, 29 Dec 2017 15:36:40 +0000, ARW wrote:

On 29/12/2017 14:43, Andrew wrote:
On 29/12/2017 14:01, George Miles wrote:
Isn't the CPC wire size bigger in blue and brown?

It changed in about 1983-ish from 1mm to 1.5mm AFAIK, but
ARW or John Rumm will no doubt confirm this. Something
to do with guaranteeing that even a non-rcd protected
circuit would trip or blow its MCB or fuse in the
required minimum period (?40 msec).

So you'll probably be ok with an RCD/RCBO or maybe even just
an MCB, but not an old-fashioned fuse arrangement.


The RCD protection will be a requirement for any new sockets and for
all T&E cables for any circuit that are buried in a wall behind plaster.

In 6 months time the regs will have changed and will require all new
domestic lighting to be RCD protected.

To what value? My board has 100mA to lights and a few other things, then
30mA to sockets, cooker etc.
I've always liked this because if the socket is tripped the lights will
probably stay on - if I've just had a shock I'd rather not be in darkness as
well!

I would expect 30mA (i.e. for shock protection rather than
infrastructure / fire protection).

However "all RCBO" installs are much more cost viable these days, and
even if just using the normal 17th style CU you would normally ensure
the power circuits in a given place are on the "other" RCD to the one
doing the lights.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Robin wrote:
No, cable should be the same size throughout the circuit. 1mm is
actually adequate for most 6A lighting circuits in houses where
the cable length isn't too long.

Is that a "should" as in "best practice" rather than as in "must"?

There's two overlapping requirements covering this.

You need to have a fused connection where cable sizes change, and a
circuit has to be fused to protect the smallest cable in the circuit.
So, if your whole circuit is fused to protect 1mm cable I would
accept a larger cable as a main feed to 1mm spurs. I have done this
where I typically have a larger cable running from the consumer unit
to a convient breakout point, where 1.5mm cable goes off to
individual lighting circuits.

I've used fuse-at-cable-change typically when spuring from a 32A ring
to provide a loft light where the lighting circuits are inaccessible
or there's a need to have a non-lighting light so you can see when
the lighting circuit is switched off. Similarly, I make sure there's
an upstairs socket within extension lead reach of downstairs and
vice versa.

jgh

On 29/12/2017 23:07, John Rumm wrote:
On 29/12/2017 17:18, wrote:
On 29/12/2017 14:01, George Miles wrote:
Is it allowed to extend an old circuit using black and red wiring with
new blue and brown. (the grey cable, not the rubbery black stuff)

Isn't the CPC wire size bigger in blue and brown?

I have several circuits (sockets and lights) running from a 'submain'
fusebox,
I'd like to use them but powering each from a separate MCB and blue
and brown cable coming from the consumer units at the other end of the
house.

Thus all fuses and trips will be in one location.

But is it allowed to mix different cables in one circuit?
And how would I calculate the maximum size of MCB per circuit?

And for lighting circuits can I run the main power line in 1.5mm and
then spurs to individual lights in 1mm squared?

Eventually I want to do full paperwork and testing and try to get it
all approved by the council under building regs.

George

I'll be doing the same in the foreseeable future and AFAICS (and from
what others have said) there is no problem.
How do you plan to extend the cables? There seems to be a lack of
agreement on whether insulated crimps are adequate for non-accessible
areas so I was wondering about using uninsulated crimps with solder
(belt'n'braces) and suitable HS sleevingÂ* ... but insulated crimps would
be less hassle ...

Good quality insulated crimps are ok. You will still need some form of
enclose for them though - so either the joint being in a box of some
sort, or the whole cable protected with heat shrink at the join.


But what defines "good quality" for crimps? I've used similar looking
crimps to these
https://www.screwfix.com/p/insulated...k-of-100/94616 in
the past (with a cycling crimp tool) but they've generally been in
(slightly) accessible locations and I've seen debate on the IET forum
about whether or not insulated crimps are reliable enough for
inaccessible locations.

On 29/12/2017 23:02, John Rumm wrote:
The single 1mm^2 CPC is undersized to ensure a fault to earth is cleared
(you need about 1.25mm^2 - the ring itself with 2 x 1.00mm^2 is ok, but
the spur is vulnerable)

When I moved into my present house, the vendors had taken all the fancy
brass sockets and switches (it was a while ago) and put back the
original 1976 white contract stuff.

But they had managed to snap the 1mm cpc in two of the sockets, which
were on a single ring (house less than 100 sq m), and badly connected
the live to a third, so that it had no cpc at all and the ring was
actually two spurs running from a 30 amp wylex rewireable fuse.

They also fitted a new kitchen and drilled right through the cooker
live wire, and then repaired it with a bit of choc block which
was hidden behind a fitted cabinet. I noticed the burn mark above
the fuse wire carrier, that had actually melted part of the metalwork
but it was 13 year before I removed the kitchen cabinet and found
the 'repair'.

In article ,
wrote:
But what defines "good quality" for crimps? I've used similar looking
crimps to these

Quite - I've seen some real rubbish on sale. Very thin metalwork. Which
simply can't grip as hard as thicker.

I only buy from TLC these days. But haven't bought any recently.

My hatred is based on their use in cars. They always give trouble -
eventually. And houses tend to have a rather longer life...

--
*Consciousness: That annoying time between naps.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman wrote:

wrote:

what defines "good quality" for crimps?

My hatred is based on their use in cars. They always give trouble -
eventually. And houses tend to have a rather longer life...

But encounter fewer pot-holes ...

On 30/12/2017 10:04, wrote:
On 29/12/2017 23:07, John Rumm wrote:

Good quality insulated crimps are ok. You will still need some form of
enclose for them though - so either the joint being in a box of some
sort, or the whole cable protected with heat shrink at the join.


But what defines "good quality" for crimps? I've used similar looking
crimps to these
https://www.screwfix.com/p/insulated...k-of-100/94616 in
the past (with a cycling crimp tool) but they've generally been in
(slightly) accessible locations and I've seen debate on the IET forum
about whether or not insulated crimps are reliable enough for
inaccessible locations.

Generally if having made a crimp, you can't pull the wire out then its a
good one... the crimp should grip hard enough to deform the wire a
little, forming a "gas tight" connection.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 30/12/2017 11:43, Dave Plowman (News) wrote:
In article ,
wrote:
But what defines "good quality" for crimps? I've used similar looking
crimps to these

Quite - I've seen some real rubbish on sale. Very thin metalwork. Which
simply can't grip as hard as thicker.

I only buy from TLC these days. But haven't bought any recently.

My hatred is based on their use in cars. They always give trouble -
eventually. And houses tend to have a rather longer life...


Are you sure its the crimped bit that causes problems and not the
connector bit they attach?

On 30/12/2017 12:10, John Rumm wrote:
On 30/12/2017 10:04, wrote:
On 29/12/2017 23:07, John Rumm wrote:

Good quality insulated crimps are ok. You will still need some form of
enclose for them though - so either the joint being in a box of some
sort, or the whole cable protected with heat shrink at the join.


But what defines "good quality" for crimps? I've used similar looking
crimps to these
https://www.screwfix.com/p/insulated...k-of-100/94616 in
the past (with a cycling crimp tool) but they've generally been in
(slightly) accessible locations and I've seen debate on the IET forum
about whether or not insulated crimps are reliable enough for
inaccessible locations.

Generally if having made a crimp, you can't pull the wire out then its a
good one... the crimp should grip hard enough to deform the wire a
little, forming a "gas tight" connection.



And don't make the mistake of thinking a ratcheting tool is always going
to make a good joint as an incorrectly adjusted one just makes a lot of
bad joints one after another.

In article ,
John Rumm wrote:
Generally if having made a crimp, you can't pull the wire out then its a
good one... the crimp should grip hard enough to deform the wire a
little, forming a "gas tight" connection.

It should. Now do a trial one using some scrap cable and cut off the
insulation. It will not be in contact all the way round the conductor, in
most cases.

Remember seeing a U-tube where various makes were run up to the full
rating of the cable, and even above. Most failed long before the cable.
Unlike a double screwed connector.

--
*I have plenty of talent and vision. I just don't care.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
dennis@home wrote:
My hatred is based on their use in cars. They always give trouble -
eventually. And houses tend to have a rather longer life...


Are you sure its the crimped bit that causes problems and not the
connector bit they attach?

Almost always the crimp. Could be worse because it is flex. Replacing with
a proper spade etc using the correct crimp tool sorts it. Of course no
connector lasts for ever. But a decent one a lot longer.

--
*Any connection between your reality and mine is purely coincidental

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
dennis@home wrote:
And don't make the mistake of thinking a ratcheting tool is always going
to make a good joint as an incorrectly adjusted one just makes a lot of
bad joints one after another.

I've got a few ratchet tools for those RBY terminals. None is adjustable.

--
*On the seventh day He brewed beer *

Dave Plowman London SW
To e-mail, change noise into sound.

On 30/12/2017 08:43, wrote:

You need to have a fused connection where cable sizes change, and a
circuit has to be fused to protect the smallest cable in the circuit.


Not true.

****ing great, send dennis off on one again.



--


Adam

On 30/12/2017 08:43, wrote:
Robin wrote:
No, cable should be the same size throughout the circuit. 1mm is
actually adequate for most 6A lighting circuits in houses where
the cable length isn't too long.

Is that a "should" as in "best practice" rather than as in "must"?

There's two overlapping requirements covering this.

You need to have a fused connection where cable sizes change,

While true for things like your example of taking a feed to run a light
fitting from a 32A socket circuit, its not universally true... For
example, an unfused 2.5mm^2 spur from a 4mm^2 radial protected by a B32
MCB.

and a
circuit has to be fused to protect the smallest cable in the circuit.

There is also some nuance in "protect" here. The fusing etc must provide
fault protection to the whole circuit, but may not be required to
provide overload protection to it all. (a spur from a ring circuit being
one example - the 32A MCB will provide fault protection for the single
run of 2.5mm^2 cable on the spur, but not overload protection. That job
is delegated to the design limitation on the spur of only feeding one
single or double socket).

So, if your whole circuit is fused to protect 1mm cable I would
accept a larger cable as a main feed to 1mm spurs. I have done this
where I typically have a larger cable running from the consumer unit
to a convient breakout point, where 1.5mm cable goes off to
individual lighting circuits.

With 6A lighting circuits, the cable sizes are over specified anyway
with regards to maximum operating current (for reasons of mechanical
durability, and limiting voltage drop).



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 30/12/2017 13:14, Dave Plowman (News) wrote:
In article ,
John Rumm wrote:
Generally if having made a crimp, you can't pull the wire out then its a
good one... the crimp should grip hard enough to deform the wire a
little, forming a "gas tight" connection.

It should. Now do a trial one using some scrap cable and cut off the
insulation. It will not be in contact all the way round the conductor, in
most cases.

Remember seeing a U-tube where various makes were run up to the full
rating of the cable, and even above. Most failed long before the cable.
Unlike a double screwed connector.

If its the one I am thinking of[1], none of the connectors failed at the
full rating of the cable. In fact they all survived well beyond a
significant overload - ultimately the cable failed before the connectors
- although that was a moot point since nothing had any insulation left
on it at that point (90A though a 2.5mm^2 wire)

[1]

https://www.youtube.com/watch?v=2uYD8e7idnY

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 30/12/2017 14:16, John Rumm wrote:
On 30/12/2017 08:43, wrote:
Robin wrote:
No, cable should be the same size throughout the circuit. 1mm is
actually adequate for most 6A lighting circuits in houses where
the cable length isn't too long.

Is that a "should" as in "best practice" rather than as in "must"?

There's two overlapping requirements covering this.

You need to have a fused connection where cable sizes change,

While true for things like your example of taking a feed to run a light
fitting from a 32A socket circuit, its not universally true...Â* For
example, an unfused 2.5mm^2 spur from a 4mm^2 radial protected by a B32
MCB.

and a
circuit has to be fused to protect the smallest cable in the circuit.

There is also some nuance in "protect" here. The fusing etc must provide
fault protection to the whole circuit, but may not be required to
provide overload protection to it all. (a spur from a ring circuit being
one example - the 32A MCB will provide fault protection for the single
run of 2.5mm^2 cable on the spur, but not overload protection. That job
is delegated to the design limitation on the spur of only feeding one
single or double socket).

I'm now more puzzled than before. I could look at the book but its not
to hand.

Earlier it was said "No, cable should be the same size throughout the
circuit. 1mm is actually adequate for most 6A lighting circuits in
houses where the cable length isn't too long."

I thought this wasn't true at the time. Can we confirm that as long as
the smallest conductor is still fault and overload protected by a MCB,
then all is well?

On Sat, 30 Dec 2017 00:51:54 +0000, John Rumm wrote:

The RCD protection will be a requirement for any new sockets and for
all T&E cables for any circuit that are buried in a wall behind plaster.

In 6 months time the regs will have changed and will require all new
domestic lighting to be RCD protected.

To what value? My board has 100mA to lights and a few other things, then
30mA to sockets, cooker etc.
I've always liked this because if the socket is tripped the lights will
probably stay on - if I've just had a shock I'd rather not be in darkness as
well!

I would expect 30mA (i.e. for shock protection rather than
infrastructure / fire protection).

However "all RCBO" installs are much more cost viable these days, and
even if just using the normal 17th style CU you would normally ensure
the power circuits in a given place are on the "other" RCD to the one
doing the lights.

RCBOs are OK for a new installation but probably wouldn't fit on the Wylex
board fitted c1992, judging by the space occupied by the MCBs.
I'd definitely go for 100mA/30mA RCDs and then RCBOs in a new installation.
--
Peter.
The gods will stay away
whilst religions hold sway

On 30/12/2017 15:16, Fredxx wrote:
On 30/12/2017 14:16, John Rumm wrote:
On 30/12/2017 08:43, wrote:
Robin wrote:
No, cable should be the same size throughout the circuit. 1mm is
actually adequate for most 6A lighting circuits in houses where
the cable length isn't too long.

Is that a "should" as in "best practice" rather than as in "must"?

There's two overlapping requirements covering this.

You need to have a fused connection where cable sizes change,

While true for things like your example of taking a feed to run a
light fitting from a 32A socket circuit, its not universally true...
For example, an unfused 2.5mm^2 spur from a 4mm^2 radial protected by
a B32 MCB.

and a
circuit has to be fused to protect the smallest cable in the circuit.

There is also some nuance in "protect" here. The fusing etc must
provide fault protection to the whole circuit, but may not be required
to provide overload protection to it all. (a spur from a ring circuit
being one example - the 32A MCB will provide fault protection for the
single run of 2.5mm^2 cable on the spur, but not overload protection.
That job is delegated to the design limitation on the spur of only
feeding one single or double socket).

I'm now more puzzled than before. I could look at the book but its not
to hand.

Earlier it was said "No, cable should be the same size throughout the
circuit. 1mm is actually adequate for most 6A lighting circuits in
houses where the cable length isn't too long."

As a general principle you would normally have just one size of cable in
a circuit, but there are some exceptions as highlighted.

I thought this wasn't true at the time.

Which bit?

Can we confirm that as long as
the smallest conductor is still fault and overload protected by a MCB,
then all is well?

Yup generally. Fault protection in particular is the one critical, must
be done at the origin of the circuit, requirements.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 29/12/2017 22:26, PeterC wrote:
On Fri, 29 Dec 2017 15:36:40 +0000, ARW wrote:

On 29/12/2017 14:43, Andrew wrote:
On 29/12/2017 14:01, George Miles wrote:
Isn't the CPC wire size bigger in blue and brown?

It changed in about 1983-ish from 1mm to 1.5mm AFAIK, but
ARW or John Rumm will no doubt confirm this. Something
to do with guaranteeing that even a non-rcd protected
circuit would trip or blow its MCB or fuse in the
required minimum period (?40 msec).

So you'll probably be ok with an RCD/RCBO or maybe even just
an MCB, but not an old-fashioned fuse arrangement.


The RCD protection will be a requirement for any new sockets and for
all T&E cables for any circuit that are buried in a wall behind plaster.

In 6 months time the regs will have changed and will require all new
domestic lighting to be RCD protected.

To what value? My board has 100mA to lights and a few other things, then
30mA to sockets, cooker etc.
I've always liked this because if the socket is tripped the lights will
probably stay on - if I've just had a shock I'd rather not be in darkness as
well!

If you have a TT installation that is about right (assuming that the
100mA RCD is time delayed if in series with the 30mA RCD).

However it will soon be a requirement for lighting to have 30mA RCD
protection on new installations. Although this has pretty much been the
case since the 17th edition came out.

--
Adam

On Sat, 30 Dec 2017 21:39:10 +0000, ARW wrote:

In 6 months time the regs will have changed and will require all new
domestic lighting to be RCD protected.

To what value? My board has 100mA to lights and a few other things, then
30mA to sockets, cooker etc.
I've always liked this because if the socket is tripped the lights will
probably stay on - if I've just had a shock I'd rather not be in darkness as
well!

If you have a TT installation that is about right (assuming that the
100mA RCD is time delayed if in series with the 30mA RCD).

However it will soon be a requirement for lighting to have 30mA RCD
protection on new installations. Although this has pretty much been the
case since the 17th edition came out.

That's a pity - I've had an experience of enough of a shock to make me jump
back - in darkness (assuming that the lighting RCD tripped) I could have
suffered an injury on various edges etc.

I can't recall if my 2 RCDs are in series or not; I suppose if 2x30mA are in
parallel, then the lighting should stay on if there's a fault on the ring.
--
Peter.
The gods will stay away
whilst religions hold sway

On 29/12/2017 14:37, Andy Burns wrote:
wrote:

George MilesÂ* wrote:

Is it allowed to extend an old circuit using black and red wiring
with new
blue and brown.

Yes.

But you should put a warning sticker on your CU(s)

https://www.labelsonline.co.uk/electrical-labels/bs7671-cable-colour-harmonisation-labels

Which has always seemed a little superfluous in domestic premises with
single phase supplies.

Red - Brown
Black - Blue

There's no mistaking which is live or neutral in either case.

SteveW