Hi,
Just about to re-wire the lighting circuit, with the Loop-in system, the
cable from switch to light has the live switch (which I know is the black
which usually has red tape attached) but ive also read of people using
another colour (Yellow and Blue I think) and Ive also noticed Twin Red core.
So whats the best combination to use?? I've also read that 1mm or 1.5mm
cable is used, is it common practice to use 1.5mm for the circuit cable and
1mm for the switching cable?
Thanks
DD

Derek Doormer wrote:

Just about to re-wire the lighting circuit, with the Loop-in system, the
cable from switch to light has the live switch (which I know is the black
which usually has red tape attached) but ive also read of people using
another colour (Yellow and Blue I think) and Ive also noticed Twin Red core.
So whats the best combination to use??

Most people use ordinary red & black for the switch 'drops', with, as
you say, red marking. Sleeving is much better than tape by the way:
easier to apply and doesn't fall off. T&E cable with two red cores is
available but never seems to have gained widespread acceptance -
probably because it sometimes helps to know which wire is the live feed
and which is the switched live. (If one of the red cores had a thin
white stripe or similar it might have caught on more.) There's also the
argument about only needing one type of cable of course.

The other colours (yellow & blue) only come into play with 2-way or
2-way and intermediate switching, where you need 3-core & earth cable
between the two-way ends (via any intermediate switches on the way). So
far as BS 7671 is concerned all cores are red - i.e. should be marked
with red sleeving. There's no fixed 'correct' use of the colours in the
3-core cable: I use red for the permanently live side, yellow between
the commons of the two-way switches and blue for the switched live side,
but many others seem to do it with the red & yellow the other way round.

You are now at liberty to use the new colours. The translation is as
follows:

Red ----- Brown
Yellow -- Black
Blue ---- Grey
Black --- Blue

I've also read that 1mm or 1.5mm cable is used, is it common practice
to use 1.5mm for the circuit cable and 1mm for the switching cable?

No, best to stick to one size throughout. 1mm^2 is almost always OK for
6A circuits. For 10A or 16A circuits you may need 1.5mm^2. Check your
cable installation conditions and grouping factors against the tables in
the OSG.

--
Andy

Derek Doormer wrote:
Hi,
Just about to re-wire the lighting circuit, with the Loop-in system, the
cable from switch to light has the live switch (which I know is the black
which usually has red tape attached) but ive also read of people using
another colour (Yellow and Blue I think) and Ive also noticed Twin Red core.
So whats the best combination to use??

Whatever you've got a 100m reel of. Most frequent is using the very same
cable throughout the lighting circuit: so, red-n-black in the "old"
style, brown-n-blue in the Modern colours. Best thing to identify the
switched-live with is a bit of red or brown (old/new) sleeving, rather
than tape - tape falls off, while sleeving stays on being trapped
between the sheath and the connection. Twin red's OK (some pedants would
argue it's "best"), but has the practical issue of needing testing to
identify which core's which (or swapping the two wires round which you
find your switch is "down" for "off"). The yellow-blue thing you're
thinking of is 3core+E - yellow, blue, red in the Olde colours, brown,
black, and grey in the New one - most often used domestically for 2- or
3-way switching, or for running both a permanent and a switched live to
e.g. a bathroom fan: not the best of things to wire simple 1-way switch
drops with.

......................................... I've also read that 1mm or 1.5mm
cable is used, is it common practice to use 1.5mm for the circuit cable and
1mm for the switching cable?

No, again it's most simple to use the same cabling throughout. While
1mmsq is "nearly always" OK, 1.5mmsq has better "headroom" when it runs
buried in or under insulation - as it often will in th'loft. The
difference in cost is usually two thirds of sod all, so if you're buying
fresh I'd go with the 1.5.

Stefek

In article ,
"Derek Doormer" writes:
Hi,
Just about to re-wire the lighting circuit, with the Loop-in system, the
cable from switch to light has the live switch (which I know is the black
which usually has red tape attached) but ive also read of people using
another colour (Yellow and Blue I think) and Ive also noticed Twin Red core.

Yellow and Blue are part of triple and earth, normally used for 2-way
switching, but not necessarily exclusively so. The twin red is intended
for the switch wire, but is rarely used in my experience. The red sleeving
is supposed to be put over the black to indicate it isn't a neutral wire.
Professional electricians seem to rarely bother with it, and I've seen it
put on the wrong wires too often to take any notice of it myself.

So whats the best combination to use??

I would suggest red and black T+E throughout with red sleeving (rather
than tape) used on the black switched live in switch drops.

I've also read that 1mm or 1.5mm
cable is used, is it common practice to use 1.5mm for the circuit cable and
1mm for the switching cable?

No. Normally you use the same for the whole circuit.
Unless the circuit is abnormally long, 1mm is fine.

Of course, you can rewire in new colours now instead,
but you should stick to one or the other.

--
Andrew Gabriel

In article ,
Andy Wade wrote:
T&E cable with two red cores is
available but never seems to have gained widespread acceptance -
probably because it sometimes helps to know which wire is the live feed
and which is the switched live.

And that it's simply an extra reel of cable to lug around. Most domestic
re-wires wouldn't use a full reel either which would make it out of favour
for DIY.

I've got some, though. ;-)

--
*Why is 'abbreviation' such a long word?

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

Cheers look forward to attempting it, 1st inspection indicates it should be
ok, as most cable are run through pretty big conduit and cables seem to move
freely, what I cant understand tho is the bloke before rewired most the
house (Even the lighting circuit) but the *ickhead rewired the lighting
circuit in 2 core with no earth!!! Presumably because he had some lying
around!
The switching cable for two way switches is annoying, looks like I only
need a few metres and buying that from one of the sheds will prolly work out
more than getting a whole reel!
Thanks for all the help, looks like new colours it is then, btw is all the
new harmonised colours in grey sheathing? cheers.
DD

"Andrew Gabriel" wrote in message
...
In article ,
"Derek Doormer" writes:
Hi,
Just about to re-wire the lighting circuit, with the Loop-in system, the
cable from switch to light has the live switch (which I know is the black
which usually has red tape attached) but ive also read of people using
another colour (Yellow and Blue I think) and Ive also noticed Twin Red
core.

Yellow and Blue are part of triple and earth, normally used for 2-way
switching, but not necessarily exclusively so. The twin red is intended
for the switch wire, but is rarely used in my experience. The red sleeving
is supposed to be put over the black to indicate it isn't a neutral wire.
Professional electricians seem to rarely bother with it, and I've seen it
put on the wrong wires too often to take any notice of it myself.

So whats the best combination to use??

I would suggest red and black T+E throughout with red sleeving (rather
than tape) used on the black switched live in switch drops.

I've also read that 1mm or 1.5mm
cable is used, is it common practice to use 1.5mm for the circuit cable
and
1mm for the switching cable?

No. Normally you use the same for the whole circuit.
Unless the circuit is abnormally long, 1mm is fine.

Of course, you can rewire in new colours now instead,
but you should stick to one or the other.

--
Andrew Gabriel

On Wed, 8 Dec 2004 19:48:36 -0000, "Derek Doormer"
strung together this:

what I cant understand tho is the bloke before rewired most the
house (Even the lighting circuit) but the *ickhead rewired the lighting
circuit in 2 core with no earth!!! Presumably because he had some lying
around!

Or more likely because it was rewired befor lighting circuits actually
had an earth.

The switching cable for two way switches is annoying, looks like I only
need a few metres and buying that from one of the sheds will prolly work out
more than getting a whole reel!

You can use two runs of T&E and use 3 of the cores for the two ways
instead of 3 core..

Thanks for all the help, looks like new colours it is then, btw is all the
new harmonised colours in grey sheathing? cheers.

Yes, as is the old coloured cable! Only way to tell is if the cores
are brown and blue as opposed to red and black. Some wholesalers book
out the new stuff with a H suffix but that isn't always the case.
--

SJW
A.C.S. Ltd
Please reply to group or use 'usenet' in email subject

In article ,
Derek Doormer wrote:
Cheers look forward to attempting it, 1st inspection indicates it should
be ok, as most cable are run through pretty big conduit and cables seem
to move freely, what I cant understand tho is the bloke before rewired
most the house (Even the lighting circuit) but the *ickhead rewired the
lighting circuit in 2 core with no earth!!! Presumably because he had
some lying around!

If he did have some 'lying around' it still makes it so old it should be
replaced. I've never seen PVC twin cable with no earth.

Are you *sure* it's not just had the earth cut off at termination points?
You'd need to strip back to be certain...

--
*Hard work has a future payoff. Laziness pays off NOW.

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

what I cant understand tho is the bloke before rewired most the
house (Even the lighting circuit) but the *ickhead rewired the lighting
circuit in 2 core with no earth!!! Presumably because he had some lying
around!

Or more likely because it was rewired befor lighting circuits actually
had an earth.

Or did it long enough ago that relying on the metallic conduit for earth
continuity was still an Acceptable Method (or was harking back to the
days when it was ;-)

Dave Plowman (News) wrote:


If he did have some 'lying around' it still makes it so old it should be
replaced. I've never seen PVC twin cable with no earth.


Last available in the '60's? - I'm old enough to remember it. :-(
--
Ian Edwards

Stefek Zaba wrote:

Or did it long enough ago that relying on the metallic conduit for earth
continuity was still an Acceptable Method (or was harking back to the
days when it was ;-)

It still is an Acceptable Method, provided that all joints are screwed
(no slip couplers allowed) [543-03-06] and that the earth terminal of
each wiring accessory is connected to an earth terminal in the
associated mounting box via a separate wire [543-02-07].

--
Andy

In article ,
Stefek Zaba wrote:
what I cant understand tho is the bloke before rewired most the
house (Even the lighting circuit) but the *ickhead rewired the lighting
circuit in 2 core with no earth!!! Presumably because he had some lying
around!

Or more likely because it was rewired befor lighting circuits actually
had an earth.

Or did it long enough ago that relying on the metallic conduit for earth
continuity was still an Acceptable Method (or was harking back to the
days when it was ;-)

To reiterate. I've seem 3/0.29 PVC with no earth, but never 1 or 1.5mm.

--
*Despite the cost of living, have you noticed how it remains so popular?

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

In article ,
Ian Edwards wrote:
If he did have some 'lying around' it still makes it so old it should
be replaced. I've never seen PVC twin cable with no earth.

Last available in the '60's? - I'm old enough to remember it. :-(

Yup. Should have said 1 or 1.5mm PVC twin cable with no earth. IMHO, TW&E
3/0.29 in PVC had become the norm long before metrication came along.
Although many simply cut off the ECC.

--
*A nest isn't empty until all their stuff is out of the attic

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

On Wed, 08 Dec 2004 23:24:05 +0000 (GMT), "Dave Plowman (News)"
strung together this:

To reiterate. I've seem 3/0.29 PVC with no earth, but never 1 or 1.5mm.

When you say reiterate do you mean it's already been 'iterated'
somewhere, or have I missed something?
--

SJW
A.C.S. Ltd
Please reply to group or use 'usenet' in email subject

In article ,
Lurch wrote:
When you say reiterate do you mean it's already been 'iterated'
somewhere, or have I missed something?

Yup.

--
*You are validating my inherent mistrust of strangers

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

In article ,
"Dave Plowman (News)" writes:
In article ,
Ian Edwards wrote:
If he did have some 'lying around' it still makes it so old it should
be replaced. I've never seen PVC twin cable with no earth.

Last available in the '60's? - I'm old enough to remember it. :-(

Yup. Should have said 1 or 1.5mm PVC twin cable with no earth. IMHO, TW&E
3/0.29 in PVC had become the norm long before metrication came along.
Although many simply cut off the ECC.

My parents house, which is somewhere in later half of 1950's,
is all PVC T&E. The earths in the lighting circuits were not
joined in the junction boxes though, they were all neatly
brought around the outside of the boxes and very tightly
twisted together in a 6" length. There are marks on the
twisted bundles which look like it was done with some tool
which did it tightly and crimped them, but without actually
leaving any crimp on the bundle.

--
Andrew Gabriel

Do you not need to earth the switching plate to the back metal box as well??
I am using chrome switches and thought it were good practice to connect it
to the mounting box?
"Andy Wade" wrote in message
...
Stefek Zaba wrote:

Or did it long enough ago that relying on the metallic conduit for earth
continuity was still an Acceptable Method (or was harking back to the
days when it was ;-)

It still is an Acceptable Method, provided that all joints are screwed (no
slip couplers allowed) [543-03-06] and that the earth terminal of each
wiring accessory is connected to an earth terminal in the associated
mounting box via a separate wire [543-02-07].

--
Andy

Have checked and cant find it anywhere, its grey sheathed with just red and
black inside theres no evidence of it being cut or pulled through!!
"Dave Plowman (News)" wrote in message
...
In article ,
Derek Doormer wrote:
Cheers look forward to attempting it, 1st inspection indicates it should
be ok, as most cable are run through pretty big conduit and cables seem
to move freely, what I cant understand tho is the bloke before rewired
most the house (Even the lighting circuit) but the *ickhead rewired the
lighting circuit in 2 core with no earth!!! Presumably because he had
some lying around!

If he did have some 'lying around' it still makes it so old it should be
replaced. I've never seen PVC twin cable with no earth.

Are you *sure* it's not just had the earth cut off at termination points?
You'd need to strip back to be certain...

--
*Hard work has a future payoff. Laziness pays off NOW.

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

Derek Doormer wrote:

Do you not need to earth the switching plate to the back metal box as well??
I am using chrome switches and thought it were good practice to connect it
to the mounting box?

Where the manufacturer provides an earth terminal to allow you to earth
accessible metal parts then, yes, it's essential good practice to use
it. This applies whether or not the incoming earth is provided by conduit.

--
Andy

Dave Plowman (News) wrote:
!

If he did have some 'lying around' it still makes it so old it should
be
replaced. I've never seen PVC twin cable with no earth.


But see Andy Wade's response to another thread about the life of PVC
T&E as follows:

"How about a technical justification for not replacing it? There's an
interesting article on cable life on the IEE web site - he
http://www.iee.org/Publish/WireRegs/...pdateApr04.pdf.

Basically the life is highly temperature dependent (Arrhenius equation,

etc.) If you take the equation in the IEE paper, with the constants
given for PVC, and massage it slightly to give the life directly in
years you get:


life in years = exp(15028/T - 40.678)


where T is the absolute (kelvin) conductor temperature of the cable.


Substituting some temperatures:


- at 70 deg. C (343 K) the life is 22.6 years (as per the paper);


- at 60 deg. C the life is 84 years;


- at 40 deg. C the life is 1,498 years!


70 deg. C corresponds, in principle, to operation at the full rated
current. Except for cables feeding space heating installations,
domestic wiring will spend the vast majority of its life at little more
than ambient temperature."

CRB