Hi all,

We recently moved to a 70s house, where from the survey, and my inspection
pre sale, the electrical installation was in pretty good nick, if somewhat
limited in numbers of sockets.

Having now spent the last few months crawling around the innards of the
house I now have a much more comprehensive understanding of the electrical
installation, and one item that initially worried me was that the power
cables, and some of the lighting cables, are in PVC insulated copper coated
aluminium cable. However, despite the well documented problems in the US
with plain aluminium cable, this Cu/Al cable seems OK. The PCV is flexible,
showing no sign of cracking or leaching, and the copper wire surface is
bright, and showing no sign of adhering to the PVC. I've now replaced about
half of the rather tatty 13A sockets, and most of the light switches, and
none of the connections were showing signs of creep, oxidation, heating, and
other nasties, which accords with the comment in
http://wiki.diyfaq.org.uk/index.php?...c_Mains_Cables re this type
of cable.

The ring cable has seven strands for phase and neutral, with an overall
diameter of 2.3mm, and a single strand CPC of 1.3mm diameter, which in terms
of its performance looks to me like a composite of imperial copper 7/029
equivalent for phase/neutral, and the equivalent of 1mm metric copper CPC.
Lighting cable has three strands at 1.4mm overall, and a 1mm CPC. Given that
the rings are on the RCD side of the CU, and are fed via 30A MCBs, it seems
to me that the cable can continue in service where necessary (with
appropriate testing.)

I can't find any information on the current capacity and performance of
Cu/Al cables - does anyone have any thoughts or info here, as to whether my
assumptions as to their continued use are correct? The cables are marked
"Enfield-Standard Johnson and Phillips 600/1000V Copperclad" incidentally.

Which brings me on to my second query. I now need to join a number of
cables, and to do it neatly in a comparatively small space. The obvious
solution is to use crimps, and the seven stranded cables will just go neatly
into blue crimps. I would, of course, use a decent ratchet crimp tool. Given
all the above a properly made crimped joint looks as though it should be
fine, but wondered if the team has any experience here?

One last comment - the wiki section on crimping
http://wiki.diyfaq.org.uk/index.php?...Cable_crimping all looks very
sensible and well laid out. I have one query though - the photos show three
blue crimps for 2.5mm T&E, which looks right for phase and neutral, but I
would have thought a red crimp (despite the unfortunate colour) would be
better for the CPC. I would assume that crimps work best if matched fairly
well in size to the conductor concerned?

Thanks for your thoughts and comments,

Charles F

On 15 Dec, 08:23, "CJF" wrote:
Hi all,

We recently moved to a 70s house, where from the survey, and my inspection
pre sale, the electrical installation was in pretty good nick, if somewhat
limited in numbers of sockets.

Having now spent the last few months crawling around the innards of the
house I now have a much more comprehensive understanding of the electrical
installation, and one item that initially worried me was that the power
cables, and some of the lighting cables, are in PVC insulated copper coated
aluminium cable. However, despite the well documented problems in the US
with plain aluminium cable, this Cu/Al cable seems OK. The PCV is flexible,
showing no sign of cracking or leaching, and the copper wire surface is
bright, and showing no sign of adhering to the PVC. I've now replaced about
half of the rather tatty 13A sockets, and most of the light switches, and
none of the connections were showing signs of creep, oxidation, heating, and
other nasties, which accords with the comment inhttp://wiki.diyfaq.org.uk/index.php?title=Historic_Mains_Cablesre this type
of cable.

The ring cable has seven strands for phase and neutral, with an overall
diameter of 2.3mm, and a single strand CPC of 1.3mm diameter, which in terms
of its performance looks to me like a composite of imperial copper 7/029
equivalent for phase/neutral, and the equivalent of 1mm metric copper CPC.
Lighting cable has three strands at 1.4mm overall, and a 1mm CPC. Given that
the rings are on the RCD side of the CU, and are fed via 30A MCBs, it seems
to me that the cable can continue in service where necessary (with
appropriate testing.)

I can't find any information on the current capacity and performance of
Cu/Al cables - does anyone have any thoughts or info here, as to whether my
assumptions as to their continued use are correct? The cables are marked
"Enfield-Standard Johnson and Phillips 600/1000V Copperclad" incidentally.

Which brings me on to my second query. I now need to join a number of
cables, and to do it neatly in a comparatively small space. The obvious
solution is to use crimps, and the seven stranded cables will just go neatly
into blue crimps. I would, of course, use a decent ratchet crimp tool. Given
all the above a properly made crimped joint looks as though it should be
fine, but wondered if the team has any experience here?

One last comment - the wiki section on crimpinghttp://wiki.diyfaq.org.uk/index.php?title=Cable_crimpingall looks very
sensible and well laid out. I have one query though - the photos show three
blue crimps for 2.5mm T&E, which looks right for phase and neutral, but I
would have thought a red crimp (despite the unfortunate colour) would be
better for the CPC. I would assume that crimps work best if matched fairly
well in size to the conductor concerned?

Thanks for your thoughts and comments,

Charles F

I remember the copperclad conductors being introduced. The copper was
electroplated onto the aluminium during manufacture and overcame the
problem of oxidation within the joints. The rule of thumb was to use a
size up on the copper equivalent to compensate for resistance
variation.
As long as the electrician kept in mid the relative softness of the
underlying material and didn't screw down so hard that the cable wa
fractured it worked fine and from your findings is still doing so.
I would be a bit dubious about using crimp conectors on the smaller
sizes due to the work hardening of the aluminium substrate. You could
of course use screw terminals and solder these if not accessible after
installation. The solder will bond well to the copper coating but use
non corosive flux.

Hi,

Agree with above, also see:

http://en.wikipedia.org/wiki/Aluminium_wire

cheers,
Pete.

CJF wrote:

One last comment - the wiki section on crimping
http://wiki.diyfaq.org.uk/index.php?...Cable_crimping all looks very
sensible and well laid out. I have one query though - the photos show three
blue crimps for 2.5mm T&E, which looks right for phase and neutral, but I
would have thought a red crimp (despite the unfortunate colour) would be
better for the CPC. I would assume that crimps work best if matched fairly
well in size to the conductor concerned?

Blue are certainly acceptable, and I expect that red are probably ok as
well.

The crimps in question:

http://wiki.diyfaq.org.uk/index.php?...table_cri mps

have acceptable cable CSAs of 0.25 to 1.65mm^2 on red, and 1.04 to
2.63mm^2 on blue. So the 1.5mm^2 CPC of a 2.5mm^2 T&E would be ok in
either.

The continuous current rating of the red ones is less - at 19A, but I
would anticipate* that their fault current withstand time ought to be
adequate to clear any likely earth fault.

* but don't have figures to hand to confirm - hence why I did not use
one in the photo.


--
Cheers,

John.

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

"John Rumm" wrote in message
...
CJF wrote:

One last comment - the wiki section on crimping
http://wiki.diyfaq.org.uk/index.php?...Cable_crimping all looks very
sensible and well laid out. I have one query though - the photos show
three
blue crimps for 2.5mm T&E, which looks right for phase and neutral, but
I
would have thought a red crimp (despite the unfortunate colour) would be
better for the CPC. I would assume that crimps work best if matched
fairly
well in size to the conductor concerned?

Blue are certainly acceptable, and I expect that red are probably ok as
well.

The crimps in question:


http://wiki.diyfaq.org.uk/index.php?...t_suitable_cri
mps

have acceptable cable CSAs of 0.25 to 1.65mm^2 on red, and 1.04 to
2.63mm^2 on blue. So the 1.5mm^2 CPC of a 2.5mm^2 T&E would be ok in
either.

The continuous current rating of the red ones is less - at 19A, but I
would anticipate* that their fault current withstand time ought to be
adequate to clear any likely earth fault.

* but don't have figures to hand to confirm - hence why I did not use
one in the photo.


--
Cheers,

John.


Good point - I hadn't taken into account that the max current on the blue
crimps was higher, and since blue and red crimps cover both 1.5mm and (just)
the older 1mm CPCs in 2.5mm T&E, the blue ones therefore seem a better bet.

Charles F

CJF wrote:
"John Rumm" wrote in message
...
CJF wrote:

One last comment - the wiki section on crimping
http://wiki.diyfaq.org.uk/index.php?...Cable_crimping all looks very
sensible and well laid out. I have one query though - the photos show
three
blue crimps for 2.5mm T&E, which looks right for phase and neutral, but
I
would have thought a red crimp (despite the unfortunate colour) would be
better for the CPC. I would assume that crimps work best if matched
fairly
well in size to the conductor concerned?
Blue are certainly acceptable, and I expect that red are probably ok as
well.

The crimps in question:


http://wiki.diyfaq.org.uk/index.php?...t_suitable_cri
mps
have acceptable cable CSAs of 0.25 to 1.65mm^2 on red, and 1.04 to
2.63mm^2 on blue. So the 1.5mm^2 CPC of a 2.5mm^2 T&E would be ok in
either.

The continuous current rating of the red ones is less - at 19A, but I
would anticipate* that their fault current withstand time ought to be
adequate to clear any likely earth fault.

* but don't have figures to hand to confirm - hence why I did not use
one in the photo.


--
Cheers,

John.


Good point - I hadn't taken into account that the max current on the blue
crimps was higher, and since blue and red crimps cover both 1.5mm and (just)
the older 1mm CPCs in 2.5mm T&E, the blue ones therefore seem a better bet.

You can tell from the earlier photo that has two blues and one red, that
initially I was going to use a red on the earth, but then realised I did
not know for sure that its current capacity would be adequate under
fault conditions. ;-)

With older T&E that has 1.00mm CPC, then there would be no downside of
using red, and they would probably offer a better mechanical fit.

--
Cheers,

John.

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

In article , CJF charles.fear
writes

I have one query though - the photos show three
blue crimps for 2.5mm T&E, which looks right for phase and neutral, but I
would have thought a red crimp (despite the unfortunate colour) would be
better for the CPC. I would assume that crimps work best if matched fairly
well in size to the conductor concerned?

I'd consider using blue crimps and overlapping the two CPCs (instead of
butting them up end to end) within the crimp to maximise the contact
area of the two jointed wires.

--
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