I have some old white-covered twin & earth mains cable with its pos & neg
insulated in red & black.

The red & black wires are both 7-strand, and each individual strand is
about 1mm thick. Where all 7 strands are tightly together, the total
thickness of each pos or neg 7-strand cable is approx 3mm (not including
the red/black insulation).

The earth wire is single-strand and approx 1.5mm thick.

The overall outside dimensions of the cable (the white outer covering) is:

13.5mm wide and 7.5mm thick.

Please tell me what this is in mm-squared terminilogy.

Many thanks indeeed...

Al

In article ,
AL_n wrote:

I have some old white-covered twin & earth mains cable with its pos & neg
insulated in red & black.

The red & black wires are both 7-strand, and each individual strand is
about 1mm thick. Where all 7 strands are tightly together, the total
thickness of each pos or neg 7-strand cable is approx 3mm (not including
the red/black insulation).

The earth wire is single-strand and approx 1.5mm thick.

The overall outside dimensions of the cable (the white outer covering) is:

13.5mm wide and 7.5mm thick.

It's probably 7/.044 which was rated at 36 A. 4.5mm is the metric
equivalent.

Please tell me what this is in mm-squared terminilogy.

Many thanks indeeed...

Al

--
Please note new email address:

charles wrote in
:

I have some old white-covered twin & earth mains cable with its pos &
neg insulated in red & black.

The red & black wires are both 7-strand, and each individual strand
is about 1mm thick. Where all 7 strands are tightly together, the
total thickness of each pos or neg 7-strand cable is approx 3mm (not
including the red/black insulation).

The earth wire is single-strand and approx 1.5mm thick.

The overall outside dimensions of the cable (the white outer
covering) is:

13.5mm wide and 7.5mm thick.

It's probably 7/.044 which was rated at 36 A. 4.5mm is the metric
equivalent.

Many thanks for that. Now for the dumb question! What is the max wattage of
electric shower I can use this for? Probably none, right?

Al

In article , AL_n
wrote:
charles wrote in
:

I have some old white-covered twin & earth mains cable with its pos &
neg insulated in red & black.

The red & black wires are both 7-strand, and each individual strand is
about 1mm thick. Where all 7 strands are tightly together, the total
thickness of each pos or neg 7-strand cable is approx 3mm (not
including the red/black insulation).

The earth wire is single-strand and approx 1.5mm thick.

The overall outside dimensions of the cable (the white outer covering)
is:

13.5mm wide and 7.5mm thick.

It's probably 7/.044 which was rated at 36 A. 4.5mm is the metric
equivalent.

Many thanks for that. Now for the dumb question! What is the max wattage
of electric shower I can use this for? Probably none, right?


do the maths - 8kW.

--
Please note new email address:

In article ,
AL_n wrote:
The red & black wires are both 7-strand, and each individual strand is
about 1mm thick. Where all 7 strands are tightly together, the total
thickness of each pos or neg 7-strand cable is approx 3mm (not including
the red/black insulation).

I'd say probably 7/0.29. That was the old equivalent of 2.5mm ring cable.
But 7/0.44" is also possible - you'd need to measure a strand more
carefully. The 0.29" etc is the diameter IIRC.

--
*Why is the time of day with the slowest traffic called rush hour?

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

charles wrote in
:

Many thanks for that. Now for the dumb question! What is the max wattage
of electric shower I can use this for? Probably none, right?


do the maths - 8kW.


Thanks; that's encouraging. I'm not challenging your math, but the TLC
cable calculator below says says I'd need 10mm cable for an 8kw shower.
(same for a 7kw one). Perhaps they factor in some overkill to cover
themselves and/or perhaps make more profit? The length of my cable run is
12metres.

Calculator I used is he

https://www.tlc-direct.co.uk/Technic...ltageDrop.html

TIA

Al

In article ,
AL_n wrote:
charles wrote in
:

Many thanks for that. Now for the dumb question! What is the max wattage
of electric shower I can use this for? Probably none, right?


do the maths - 8kW.


Thanks; that's encouraging. I'm not challenging your math, but the TLC
cable calculator below says says I'd need 10mm cable for an 8kw shower.
(same for a 7kw one). Perhaps they factor in some overkill to cover
themselves and/or perhaps make more profit? The length of my cable run
is 12metres.

Calculator I used is he

https://www.tlc-direct.co.uk/Technic...ltageDrop.html

You first need to make *absolutely* sure what the cable you have is. The
13.5mm overall width of the T&E says to me it's more likely 7/0.29. That
was a lot wider than 2.5mm TW&E.

Measure a strand with a digital caliper.

--
*Support bacteria - they're the only culture some people have *

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

Dave Plowman (News) wrote:
In article ,
AL_n wrote:
The red & black wires are both 7-strand, and each individual strand is
about 1mm thick. Where all 7 strands are tightly together, the total
thickness of each pos or neg 7-strand cable is approx 3mm (not including
the red/black insulation).

I'd say probably 7/0.29. That was the old equivalent of 2.5mm ring cable.
But 7/0.44" is also possible - you'd need to measure a strand more
carefully. The 0.29" etc is the diameter IIRC.

Erm 0.029" I think you mean.

The problem is the OP said about 1mm and 0.029" is under 3/4mm

Accurate measurements and simple calculation is needed.

"Bob Minchin" wrote in message ...

Dave Plowman (News) wrote:
In article ,
AL_n wrote:
The red & black wires are both 7-strand, and each individual strand is
about 1mm thick. Where all 7 strands are tightly together, the total
thickness of each pos or neg 7-strand cable is approx 3mm (not including
the red/black insulation).

I'd say probably 7/0.29. That was the old equivalent of 2.5mm ring cable.
But 7/0.44" is also possible - you'd need to measure a strand more
carefully. The 0.29" etc is the diameter IIRC.

Erm 0.029" I think you mean.

The problem is the OP said about 1mm and 0.029" is under 3/4mm

Accurate measurements and simple calculation is needed.


The only 7/ 029 I've worked with was TRS which in that era invariably was
black. O/P iirc is saying a white sheath.

Andrew

On 19/06/2015 19:17, Andrew Mawson wrote:

The only 7/ 029 I've worked with was TRS which in that era invariably
was black. O/P iirc is saying a white sheath.

I've come across plenty of PVC 7/029 in the past, but only grey.

--
Mike Clarke

In article ,
Dave Plowman (News) wrote:
In article ,
AL_n wrote:
charles wrote in
:

Many thanks for that. Now for the dumb question! What is the max wattage
of electric shower I can use this for? Probably none, right?


do the maths - 8kW.


Thanks; that's encouraging. I'm not challenging your math, but the TLC
cable calculator below says says I'd need 10mm cable for an 8kw shower.
(same for a 7kw one). Perhaps they factor in some overkill to cover
themselves and/or perhaps make more profit? The length of my cable run
is 12metres.

Calculator I used is he

https://www.tlc-direct.co.uk/Technic...ltageDrop.html

You first need to make *absolutely* sure what the cable you have is. The
13.5mm overall width of the T&E says to me it's more likely 7/0.29. That
was a lot wider than 2.5mm TW&E.

I don't have any 7/029 clips left (I do have 1/029 though), but 2.5mm clips
are only 10mm across. That's why I suspected 7/044. The stranmg diameter
also seem to agree with .044

--
Please note new email address:

In article , Andrew Mawson
wrote:
"Bob Minchin" wrote in message ...

Dave Plowman (News) wrote:
In article , AL_n
wrote:
The red & black wires are both 7-strand, and each individual strand
is about 1mm thick. Where all 7 strands are tightly together, the
total thickness of each pos or neg 7-strand cable is approx 3mm (not
including the red/black insulation).

I'd say probably 7/0.29. That was the old equivalent of 2.5mm ring
cable. But 7/0.44" is also possible - you'd need to measure a strand
more carefully. The 0.29" etc is the diameter IIRC.

Erm 0.029" I think you mean.

The problem is the OP said about 1mm and 0.029" is under 3/4mm

Accurate measurements and simple calculation is needed.


The only 7/ 029 I've worked with was TRS which in that era invariably was
black. O/P iirc is saying a white sheath.

No, there was PVC in Imperial sizes. I re-wired my house in in 1964 using
PVC.

--
Please note new email address:

In article ,
AL_n wrote:
charles wrote in
:

Many thanks for that. Now for the dumb question! What is the max wattage
of electric shower I can use this for? Probably none, right?


do the maths - 8kW.


Thanks; that's encouraging. I'm not challenging your math, but the TLC
cable calculator below says says I'd need 10mm cable for an 8kw shower.
(same for a 7kw one). Perhaps they factor in some overkill to cover
themselves and/or perhaps make more profit? The length of my cable run is
12metres.

Calculator I used is he

https://www.tlc-direct.co.uk/Technic...ltageDrop.html

12m is quite a long cable run for a shower, so yes, you might need a
thicker cable.

--
Please note new email address:

On Friday, 19 June 2015 16:16:51 UTC+1, AL_n wrote:
I have some old white-covered twin & earth mains cable with its pos & neg
insulated in red & black.

The red & black wires are both 7-strand, and each individual strand is
about 1mm thick. Where all 7 strands are tightly together, the total
thickness of each pos or neg 7-strand cable is approx 3mm (not including
the red/black insulation).

The earth wire is single-strand and approx 1.5mm thick.

The overall outside dimensions of the cable (the white outer covering) is:

13.5mm wide and 7.5mm thick.

Please tell me what this is in mm-squared terminilogy.

Many thanks indeeed...

Al


As the earth wire is single strand, it must be 7/029.
Rated at 20 amps, equivalent to 2.5mm these days.

Commonly used for wiring sockets, usually a ring main

On 19/06/2015 16:16, AL_n wrote:
I have some old white-covered twin & earth mains cable with its pos & neg
insulated in red & black.

The red & black wires are both 7-strand, and each individual strand is
about 1mm thick. Where all 7 strands are tightly together, the total
thickness of each pos or neg 7-strand cable is approx 3mm (not including
the red/black insulation).

The earth wire is single-strand and approx 1.5mm thick.

The overall outside dimensions of the cable (the white outer covering) is:

13.5mm wide and 7.5mm thick.

If you go from the overall size, and compare with the figures in the
last column of the table he

http://wiki.diyfaq.org.uk/index.php?...es#Cable_Sizes

That suggests something around the 6mm^2 mark, or its imperial equal.



--
Cheers,

John.

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

On 19/06/2015 20:49, harry wrote:
On Friday, 19 June 2015 16:16:51 UTC+1, AL_n wrote:
I have some old white-covered twin & earth mains cable with its pos & neg
insulated in red & black.

The red & black wires are both 7-strand, and each individual strand is
about 1mm thick. Where all 7 strands are tightly together, the total
thickness of each pos or neg 7-strand cable is approx 3mm (not including
the red/black insulation).

The earth wire is single-strand and approx 1.5mm thick.

The overall outside dimensions of the cable (the white outer covering) is:

13.5mm wide and 7.5mm thick.

Please tell me what this is in mm-squared terminilogy.

Many thanks indeeed...

Al


As the earth wire is single strand, it must be 7/029.
Rated at 20 amps, equivalent to 2.5mm these days.

While 7/.029" could be treated as roughly equal to 2.5mm^2 these days
(it actually a bit more), its inappropriate to describe it as "20 amps".
The rating will depend on the installation method.

The 14th edition quotes a "clipped direct" rating of 25A, which seems
rather conservative given that's less than the 27A quoted for 2.5mm^2 in
the same circumstances these days.

Commonly used for wiring sockets, usually a ring main



--
Cheers,

John.

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

On Friday, 19 June 2015 23:21:55 UTC+1, John Rumm wrote:
The 14th edition quotes a "clipped direct" rating of 25A, which seems
rather conservative given that's less than the 27A quoted for 2.5mm^2 in
the same circumstances these days.

But the 14th Edition would assume rewireable fuse, but the current edition assumes MCB and has an optional derating for rewireable fuse?

Owain

On 20/06/2015 00:42, wrote:
On Friday, 19 June 2015 23:21:55 UTC+1, John Rumm wrote:
The 14th edition quotes a "clipped direct" rating of 25A, which
seems rather conservative given that's less than the 27A quoted for
2.5mm^2 in the same circumstances these days.

But the 14th Edition would assume rewireable fuse, but the current
edition assumes MCB and has an optional derating for rewireable
fuse?

Indeed, there is a de-rating factor 0.725 allocated for re-wireable
fuses now. Hence my comment about 25A rating being conservative in a
modern setting - the 2.9mm^2 that 7/.029 is approximately in modern
money, would probably have a clipped direct rating of around 34A with
MCB protection.



--
Cheers,

John.

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

John Rumm wrote in
:

13.5mm wide and 7.5mm thick.

If you go from the overall size, and compare with the figures in the
last column of the table he

http://wiki.diyfaq.org.uk/index.php?...es#Cable_Sizes

That suggests something around the 6mm^2 mark, or its imperial equal.


I measured another piece of this cable. I am relying on a tape-measure, not
a micrometer; the OD appears to be to be possibly 7mm x 13.5mm, which is
close to the '6.8 x 13.1' stated as the OD of 6mm^ cable. However, would
the insulation thicknesses be the same in the 1970s/1980s as it is today?

Somewhere buried in my house, I have an imperial micrometer. If I can
somehow manage to find it, I'll be able to measure the exact thicknesses of
the copper wires.

6mm^ certainly does ring a mental bell. ISTR seeing a lot of it in the late
1980s. ISTR using it to run power to a Baby Belling (small) cooker back in
the early 1990s..

Anyway, assuming it is 6mm^, and I use a circuit breaker at the end of my
12m run, I would like to use it to feed a 7.5kw shower.

I have some vague recollection of hearing someone say it was frowned-upon
to connect two or three shorter lengths of this stuff together, when
feeding a high-wattage appliance. It that a hard-and-fast rule, or is it
okay to have a couple or more joints using those round, hard plastic 30A
junction boxes?


Thanks to all for the help.
Al

In article ,
Bob Minchin wrote:
I'd say probably 7/0.29. That was the old equivalent of 2.5mm ring cable.
But 7/0.44" is also possible - you'd need to measure a strand more
carefully. The 0.29" etc is the diameter IIRC.

Erm 0.029" I think you mean.

I did, sorry.

The problem is the OP said about 1mm and 0.029" is under 3/4mm

I'd rather an accurate measurement than 'about'

And the overall diameter of the conductor was said to be about 3mm, which
says 7/0.029 to me.

But I don't have any handy to check.

The only way is to measure a single stand *accurately*.

Accurate measurements and simple calculation is needed.

--
*The more people I meet, the more I like my dog.

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

In article ,
Andrew Mawson wrote:
The only 7/ 029 I've worked with was TRS which in that era invariably
was black. O/P iirc is saying a white sheath.

7/0.029 came in both grey and white PVC too. If it was older rubber, then
yes, black.

--
*If you can read this, thank a teecher

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

In article ,
charles wrote:
You first need to make *absolutely* sure what the cable you have is.
The 13.5mm overall width of the T&E says to me it's more likely
7/0.29. That was a lot wider than 2.5mm TW&E.

I don't have any 7/029 clips left (I do have 1/029 though), but 2.5mm
clips are only 10mm across.

7/0.029 TW&E was a lot wider than 2.5mm. At first glance it looked more
like the next size up in metric.


That's why I suspected 7/044. The stranmg
diameter also seem to agree with .044

--
*I must always remember that I'm unique, just like everyone else. *

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

In article ,
AL_n wrote:
I measured another piece of this cable. I am relying on a tape-measure,
not a micrometer; the OD appears to be to be possibly 7mm x 13.5mm,
which is close to the '6.8 x 13.1' stated as the OD of 6mm^ cable.
However, would the insulation thicknesses be the same in the
1970s/1980s as it is today?

Simply not the way to measure it. Imperial cable external dimensions were
much larger than the equivalent metric.

Imperial lighting TW&E 3/0.029 was approx the same outside size as 2.5mm
TW&E.

It's also far more likely to find 7/0.029 cable lying around. Larger stuff
in those days only likely used for an electric cooker - showers were rare
if they even existed.

--
*They told me I had type-A blood, but it was a Type-O.*

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

On 20/06/2015 10:19, AL_n wrote:
John Rumm wrote in
:

13.5mm wide and 7.5mm thick.

If you go from the overall size, and compare with the figures in the
last column of the table he

http://wiki.diyfaq.org.uk/index.php?...es#Cable_Sizes

That suggests something around the 6mm^2 mark, or its imperial equal.


I measured another piece of this cable. I am relying on a tape-measure, not
a micrometer; the OD appears to be to be possibly 7mm x 13.5mm, which is
close to the '6.8 x 13.1' stated as the OD of 6mm^ cable. However, would
the insulation thicknesses be the same in the 1970s/1980s as it is today?

For PVC they are likely to be similar - but the overall cable sheath
size was not standardised then or now - so its not a cast iron
guarantee. You will need to get a calliper on the conductors to be sure.

Somewhere buried in my house, I have an imperial micrometer. If I can
somehow manage to find it, I'll be able to measure the exact thicknesses of
the copper wires.

Yup, that's what you need to be certain.

6mm^ certainly does ring a mental bell. ISTR seeing a lot of it in the late
1980s. ISTR using it to run power to a Baby Belling (small) cooker back in
the early 1990s..

Yup, its commonly used for cookers, and used to be used for showers when
they were more modest in power than many modern ones.

Anyway, assuming it is 6mm^, and I use a circuit breaker at the end of my
12m run, I would like to use it to feed a 7.5kw shower.

You will need RCD protection now (17th edition rules) as well.

To check any cable for adequacy, run through the procedure described he

http://wiki.diyfaq.org.uk/index.php?...g_A_Cable_Size

I have some vague recollection of hearing someone say it was frowned-upon
to connect two or three shorter lengths of this stuff together, when
feeding a high-wattage appliance. It that a hard-and-fast rule, or is it
okay to have a couple or more joints using those round, hard plastic 30A
junction boxes?

With high current circuits, you have most risk of heating at the
termination points. So the more you have, the more "risk" if you like.
However if you do the job correctly and make the terminations tightly
(or better still crimp or solder them), there there is no problem
joining cables.

You will have difficulty getting 2 x 6mm^2 into many junction boxes, so
look for one of the high current ones designed for the application.

Something like:

https://www.tlc-direct.co.uk/Products/LB9065.html

may be a better bet.


--
Cheers,

John.

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

On 20/06/2015 10:19, AL_n wrote:
John Rumm wrote in
:

13.5mm wide and 7.5mm thick.

If you go from the overall size, and compare with the figures in the
last column of the table he

http://wiki.diyfaq.org.uk/index.php?...es#Cable_Sizes

That suggests something around the 6mm^2 mark, or its imperial equal.


I measured another piece of this cable. I am relying on a tape-measure, not
a micrometer; the OD appears to be to be possibly 7mm x 13.5mm, which is
close to the '6.8 x 13.1' stated as the OD of 6mm^ cable. However, would
the insulation thicknesses be the same in the 1970s/1980s as it is today?

Somewhere buried in my house, I have an imperial micrometer. If I can
somehow manage to find it, I'll be able to measure the exact thicknesses of
the copper wires.

6mm^ certainly does ring a mental bell. ISTR seeing a lot of it in the late
1980s. ISTR using it to run power to a Baby Belling (small) cooker back in
the early 1990s..

Anyway, assuming it is 6mm^, and I use a circuit breaker at the end of my
12m run, I would like to use it to feed a 7.5kw shower.

I have some vague recollection of hearing someone say it was frowned-upon
to connect two or three shorter lengths of this stuff together, when
feeding a high-wattage appliance. It that a hard-and-fast rule, or is it
okay to have a couple or more joints using those round, hard plastic 30A
junction boxes?


Thanks to all for the help.
Al

If you have some digital kitchen scales, you could always cut off a
fixed length of the 7 strands , weigh it (the copper) and work out the
crossectional area. About 20cms should give enough accuracy to
differentiate 2.5, 4 and 6mm^2 cores ( assuming 1g accuracy on scales).
Copper is 8.96 g cm^-3

On 19/06/15 17:54, AL_n wrote:
charles wrote in
:

I have some old white-covered twin & earth mains cable with its pos &
neg insulated in red & black.

The red & black wires are both 7-strand, and each individual strand
is about 1mm thick. Where all 7 strands are tightly together, the
total thickness of each pos or neg 7-strand cable is approx 3mm (not
including the red/black insulation).

The earth wire is single-strand and approx 1.5mm thick.

The overall outside dimensions of the cable (the white outer
covering) is:

13.5mm wide and 7.5mm thick.

It's probably 7/.044 which was rated at 36 A. 4.5mm is the metric
equivalent.

Many thanks for that. Now for the dumb question! What is the max wattage of
electric shower I can use this for? Probably none, right?

Al


My understanding is you should use the 'new colours' for new
installations. If you have the installation checked, and being a shower
you should, then you may have a problem.

I'm not trying to be officious, just helping you avoid potential issues.

We had a new kitchen installed several years back which required some
electrical work, including 'spurs' (new colours) etc. for the induction
hob, double oven and the like, and a new consumer unit. As the existing
wiring has the 'old colours' a there is a note warning that the
installation has 'mixed colours' and the whole installation was checked
under the dreaded 'part P' as part of the contract.

"Brian Reay" wrote in message
...


My understanding is you should use the 'new colours' for new
installations.


Correct.

If this is indeed a new installation then one wonders why the OP is asking
the question and is not just fitting 10mm T&E and fitting a higher rated
shower.


I suspect that some of the cable is already in place and the OP wants to
reuse it.


--
Adam

Another point, don't skimp on the shower itself.

We've had cheaper, 7kW or so, showers in the past than they were never
really that good. They worked but you couldn't get a 'hot' shower, and
they were prone to cutting out due to thinking they were too hot. They
were the better end of the 7kW range.

We now have a Mira Advance ATL and can't fault it*. It is 9kW and you
can have it as hot as you are likely to want, with a good flow rate.
They aren't cheap but, in my view, worth the money.

*Well, I saw we can't fault it, my wife doesn't like the blue LEDs but
she has a 'thing' about blue LEDs.

There may be other makes of course, I'm just going by our experience.

On 20/06/2015 14:52, Brian Reay wrote:
On 19/06/15 17:54, AL_n wrote:
charles wrote in
:

I have some old white-covered twin & earth mains cable with its pos &
neg insulated in red & black.

The red & black wires are both 7-strand, and each individual strand
is about 1mm thick. Where all 7 strands are tightly together, the
total thickness of each pos or neg 7-strand cable is approx 3mm (not
including the red/black insulation).

The earth wire is single-strand and approx 1.5mm thick.

The overall outside dimensions of the cable (the white outer
covering) is:

13.5mm wide and 7.5mm thick.

It's probably 7/.044 which was rated at 36 A. 4.5mm is the metric
equivalent.

Many thanks for that. Now for the dumb question! What is the max
wattage of
electric shower I can use this for? Probably none, right?

Al


My understanding is you should use the 'new colours' for new
installations. If you have the installation checked, and being a shower
you should, then you may have a problem.

There is no requirement to replace an existing cable though it its
adequate for the job.

I'm not trying to be officious, just helping you avoid potential issues.

In the real world its really a non issue IME. Conveyancing solicitors
etc long since lost interest in electrics.

We had a new kitchen installed several years back which required some
electrical work, including 'spurs' (new colours) etc. for the induction
hob, double oven and the like, and a new consumer unit. As the existing
wiring has the 'old colours' a there is a note warning that the
installation has 'mixed colours' and the whole installation was checked
under the dreaded 'part P' as part of the contract.

If worried, say you are happy for the purchaser to have inspection done
at their expense, under the understanding that there will be no price
reduction or remedial action taken regardless of the outcome! Its a
sellers market at the moment ;-)



--
Cheers,

John.

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

In article , Brian Reay wrote:
On 19/06/15 17:54, AL_n wrote:
charles wrote in
:

I have some old white-covered twin & earth mains cable with its pos &
neg insulated in red & black.

The red & black wires are both 7-strand, and each individual strand
is about 1mm thick. Where all 7 strands are tightly together, the
total thickness of each pos or neg 7-strand cable is approx 3mm (not
including the red/black insulation).

The earth wire is single-strand and approx 1.5mm thick.

The overall outside dimensions of the cable (the white outer
covering) is:

13.5mm wide and 7.5mm thick.

It's probably 7/.044 which was rated at 36 A. 4.5mm is the metric
equivalent.

Many thanks for that. Now for the dumb question! What is the max
wattage of electric shower I can use this for? Probably none, right?

Al


My understanding is you should use the 'new colours' for new
installations. If you have the installation checked, and being a shower
you should, then you may have a problem.

I understand that if you mark the ends with the new colours then it is
permissable to use cable to the old spec.

--
Please note new email address:

Robert wrote in news:cul7urFs2q1U1
@mid.individual.net:


If you have some digital kitchen scales, you could always cut off a
fixed length of the 7 strands , weigh it (the copper) and work out the
crossectional area. About 20cms should give enough accuracy to
differentiate 2.5, 4 and 6mm^2 cores ( assuming 1g accuracy on scales).
Copper is 8.96 g cm^-3

Thanks for the tip. I cut off 200mm off one of the 7-strand wires, and
after stripping, it weighs 11g (to the nearest g, I guess since it doesn't
register decimals). That was using an electronic letter scale. I checked
the reading on a second electronic letter scale, and got the same reading.

Unfortunately math is one of my worst subjects and I can't get my head
around the formula to calculate what I need to know. Can anyone tell me
what the cable is now?

Al

John Rumm wrote in news:qNKdnfS-
:

If worried, say you are happy for the purchaser to have inspection done
at their expense, under the understanding that there will be no price
reduction or remedial action taken regardless of the outcome! Its a
sellers market at the moment ;-)

I must remember that one; I like it!

Al

"ARW" wrote in news:mm3s4o$6m8$1@dont-
email.me:

I suspect that some of the cable is already in place and the OP wants to
reuse it.

Good deduction! Actually, the whole house is wired in matching white-
covered, red+black inner cables, so at least it'll all be cosistent.

Al

In article , says...
My understanding is you should use the 'new colours' for new
installations. If you have the installation checked, and being a shower
you should, then you may have a problem.

I'm not trying to be officious, just helping you avoid potential issues.


Provided the cable is sleeved with the correct colour at its
terminations, then it meets current regulations (514.3.2).

AL_n wrote:

I cut off 200mm off one of the 7-strand wires, and after stripping,
it weighs 11g Can anyone tell me what the cable is now?

Seems equivalent to 6mm^2

http://www.wolframalpha.com/input/?i=11+grams+%2F+200mm+%2F+density+of+copper

Andy Burns wrote in
o.uk:

I cut off 200mm off one of the 7-strand wires, and after stripping,
it weighs 11g Can anyone tell me what the cable is now?

Seems equivalent to 6mm^2

Many thanks!

Al

Brian Reay wrote in :

Another point, don't skimp on the shower itself.

We've had cheaper, 7kW or so, showers in the past than they were never
really that good. They worked but you couldn't get a 'hot' shower, and
they were prone to cutting out due to thinking they were too hot. They
were the better end of the 7kW range.

Thanks for the tip. I'll be sure to keep the guarantee, whatever I get.
Then if it gives me any gyp I can take it back. I feel sure that a 7.5Kw
will be adequate, as I always prefer a modest water flow from a shower.
That's partly because the shower will be over a bath with a shower curtain,
and I don't like any ovespray getting onto the floor etc.

Al

On Fri, 19 Jun 2015 19:59:55 +0100, charles wrote:

In article ,
AL_n wrote:
charles wrote in
:

Many thanks for that. Now for the dumb question! What is the max wattage
of electric shower I can use this for? Probably none, right?


do the maths - 8kW.


Thanks; that's encouraging. I'm not challenging your math, but the TLC
cable calculator below says says I'd need 10mm cable for an 8kw shower.
(same for a 7kw one). Perhaps they factor in some overkill to cover
themselves and/or perhaps make more profit? The length of my cable run is
12metres.

Calculator I used is he

https://www.tlc-direct.co.uk/Technic...ltageDrop.html

12m is quite a long cable run for a shower, so yes, you might need a
thicker cable.

Voltage drop for 240V is negligible. It's how well insulated the run is that matters, not the length.

--
Mary had a little lamb, it walked into a pylon. 10,000 volts went up its arse, and turned its wool to nylon.

On Sat, 20 Jun 2015 18:58:44 +0100, AL_n wrote:

"ARW" wrote in news:mm3s4o$6m8$1@dont-
email.me:

I suspect that some of the cable is already in place and the OP wants to
reuse it.

Good deduction! Actually, the whole house is wired in matching white-
covered, red+black inner cables, so at least it'll all be cosistent.

The only problem with having mixed colours is when you have 3 phase in the building. Black can be live or neutral. And I saw the consequences - 40 broken computers and a fair bit of a stink when they got 2 phase given to them. Fixed them all by replacing the capacitors though, which the insurance company didn't think of.

--
Love conquers all, except in tennis.

In article , Tough Guy no. 1265
wrote:
On Fri, 19 Jun 2015 19:59:55 +0100, charles
wrote:

In article , AL_n
wrote:
charles wrote in
:

Many thanks for that. Now for the dumb question! What is the max
wattage of electric shower I can use this for? Probably none, right?


do the maths - 8kW.


Thanks; that's encouraging. I'm not challenging your math, but the TLC
cable calculator below says says I'd need 10mm cable for an 8kw
shower. (same for a 7kw one). Perhaps they factor in some overkill to
cover themselves and/or perhaps make more profit? The length of my
cable run is 12metres.

Calculator I used is he

https://www.tlc-direct.co.uk/Technic...ltageDrop.html

12m is quite a long cable run for a shower, so yes, you might need a
thicker cable.

Voltage drop for 240V is negligible. It's how well insulated the run is
that matters, not the length.

The voltage drop will be the same for any voltage - it's dependant on
current. Insulation doesn't affect voltage drop.