Hi,

I am working my way round the house room by room, and have just started on
the sun lounge.

I have an arrangement of two sockets side by side in a fancy double wall
box.
One socket is a single 13 amp 3 pin, the other is a single round pin 3 pin
(like the old 5 amp IIRC).

The wiring is grey sheathed T&E 1mm or 1.5mm AFAICS and wired as a ring
i.e. two cables both wired into the socket.

The extension was built in the sixties or seventies (we think) and this
wiring will have been done then. The wiring in the rest of the house does
not use this scheme.

As far as I can tell this is not current(no pun intended)ly in use but
when I put my cheapo digital multimeter on the A/C setting it shows U/L
(overload) very briefly then settles down to showing about 9V between the
live pin and the neutral pin or the earth pin; earth and neutral are at
the same level. I assume that this is acceptable.

I am assuming that there is no connection to anything live, and wondering
what this may have been used for in the past.

I was considering replacing the wall box to allow me to fit a twin socket,
but looking at this the easiest thing to do would be to add another single
socket to replace the round pin socket. Probably as a spur depending on
the amount of free cable. Is there any benefit in doing this over using a
distribution board/extension lead?

Bit of a rambling post, but there you go.

Cheers

Dave R

David WE Roberts wrote:
Hi,

I am working my way round the house room by room, and have just started on
the sun lounge.

I have an arrangement of two sockets side by side in a fancy double wall
box.
One socket is a single 13 amp 3 pin, the other is a single round pin 3 pin
(like the old 5 amp IIRC).

The wiring is grey sheathed T&E 1mm or 1.5mm AFAICS and wired as a ring
i.e. two cables both wired into the socket.

The extension was built in the sixties or seventies (we think) and this
wiring will have been done then. The wiring in the rest of the house does
not use this scheme.

As far as I can tell this is not current(no pun intended)ly in use but
when I put my cheapo digital multimeter on the A/C setting it shows U/L
(overload) very briefly then settles down to showing about 9V between the
live pin and the neutral pin or the earth pin; earth and neutral are at
the same level. I assume that this is acceptable.

A digital voltmeter is probably the worst way of measuring these
voltages as they (digital meters) have such high input impedance any
coupled voltage is read. An moving coil type of meter would be better if
you can get hold of one to test the circuit. Failing that, a resistor
say 10k ohm or thereabouts connected across the digital meter terminals
would shunt the meter and give more meaningful measurements.


Steve

David WE Roberts wrote:

As far as I can tell this is not current(no pun intended)ly in use but
when I put my cheapo digital multimeter on the A/C setting it shows U/L
(overload) very briefly then settles down to showing about 9V between the
live pin and the neutral pin or the earth pin; earth and neutral are at
the same level. I assume that this is acceptable.

Its is probably telling you that the other end of the wires is not
connected to anything or at least switched off. Your meter is reading
the voltage on the wire induced by its proximity to other live wires.
The difficulty with a DVM here is it places so little load on the wire
that it does not discharge it easily.

I am assuming that there is no connection to anything live, and wondering
what this may have been used for in the past.

I was considering replacing the wall box to allow me to fit a twin socket,
but looking at this the easiest thing to do would be to add another single
socket to replace the round pin socket. Probably as a spur depending on
the amount of free cable. Is there any benefit in doing this over using a
distribution board/extension lead?

You would need to check the T&E cable size carefully first to make sure
it really is suitable.

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


--
Cheers,

John.

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

On 21 Oct, 16:30, David WE Roberts wrote:

I have an arrangement of two sockets side by side in a fancy double wall
box.
One socket is a single 13 amp 3 pin, the other is a single round pin 3 pin
(like the old 5 amp IIRC).

Round-pin sockets are commonly used for lighting (table or standard
lamp) switched from elsewhere. Does it become live when you turn on
the room light? Is there an extra wire inside the light switch? Or a
mystery switch somewhere that appears to do nothing?

The wiring is grey sheathed T&E 1mm or 1.5mm AFAICS and wired as a ring
i.e. two cables both wired into the socket.

You could try tracing the cable routes with a detector, though the
neigbouring 13A socket will probably confuse things. The presence of
two cables to the mystery socket suggests there is/was a second one
somewhere.

Chris

On Sun, 21 Oct 2007 16:42:49 +0100, John Rumm wrote:

David WE Roberts wrote:

As far as I can tell this is not current(no pun intended)ly in use but
when I put my cheapo digital multimeter on the A/C setting it shows U/L
(overload) very briefly then settles down to showing about 9V between the
live pin and the neutral pin or the earth pin; earth and neutral are at
the same level. I assume that this is acceptable.

Its is probably telling you that the other end of the wires is not
connected to anything or at least switched off. Your meter is reading
the voltage on the wire induced by its proximity to other live wires.
The difficulty with a DVM here is it places so little load on the wire
that it does not discharge it easily.
********
Good point - (following on from another post) I have one light switch
which doesn't seem to do anything.
I will check this and test the socket with the light switch on. If this is
a switched circuit then I will have to work out where it comes from then
decide if I can safely disconnect it or if I label it up and/or use it.
********
I am assuming that there is no connection to anything live, and
wondering what this may have been used for in the past.

I was considering replacing the wall box to allow me to fit a twin
socket, but looking at this the easiest thing to do would be to add
another single socket to replace the round pin socket. Probably as a
spur depending on the amount of free cable. Is there any benefit in
doing this over using a distribution board/extension lead?

You would need to check the T&E cable size carefully first to make sure
it really is suitable.

I'm not sure I explained myself correctly.
I was considering removing the current cabling to the round pin socket,
and connecting a second 13 Amp single socket to the one next to it.

To clarify - I have an extended double wall box which will take two
single sockets (and is too wide for a double socket).
One single socket is switched 13 Amp.
The other single socket is round pin (5 amp?)

I propose to replace the round pin socket with another single 13 Amp
socket and either link it into the ring or spur it off the other 13 Amp
socket depending on available cable length. Spur is the most likely. The
13 Amp ring is standard 2.5mm T&E. I do not plan to reuse the 1mm/1.5mm
cable currently connected to the round pin socket.

There are three sets of sockets in the extension. Two have a 13 Amp and a
round pin pair; the third also has a telephone socket.

Cheers

Dave R

David WE Roberts wrote:
snip
There are three sets of sockets in the extension. Two have a 13 Amp and a
round pin pair; the third also has a telephone socket.
/snip

I'm not sure, but I think the 'phone people may get antsy about that.

ISTR having an office with 3-sided poles to get wires from the false
ceiling to a usable level; the installers said that the 'phone people
didn't like their signals too close to the mains, and that was why the
three sides were phone, mains, data. OTOH, that was a long time ago,
*and* was a private exchange...

Andy

Andy Champ wrote:
OTOH, that was a long time ago, *and* was a private exchange...

Ooh! In the thread "Part P is not going away ?" Rumble just said "In
fact the signal cables may well be part of a fixed installation and if
they were, they would be subject to Regulation 528 (segregation,
separation, etc)" so perhaps I am onto something!

Andy

Andy Champ wrote:
Andy Champ wrote:
OTOH, that was a long time ago, *and* was a private exchange...

Ooh! In the thread "Part P is not going away ?" Rumble just said "In
fact the signal cables may well be part of a fixed installation and if
they were, they would be subject to Regulation 528 (segregation,
separation, etc)" so perhaps I am onto something!

Andy
It has ALWAYS been part of electric regs to segregate low voltage and
signal cables from mains, in seperate trunking (areas?) and if not, by
distance.

On Mon, 22 Oct 2007 02:54:15 +0100 someone who may be The Natural
Philosopher wrote this:-

It has ALWAYS been part of electric regs to segregate low voltage and
signal cables from mains, in seperate trunking (areas?) and if not, by
distance.

All the cables inside a house or commercial building are likely to
be low voltage, or extra-low voltage and when discussing the wiring
regulations people who are familiar with them tend to stick to the
correct terms.

Segregation in the regulations is largely considered in terms of
safety. There is no restriction on having low voltage and extra-low
voltage cables in the same enclosure, provided the extra low voltage
cables are insulated to the higher voltage, including barriers at
boxes, or separated by earthed metal. They can even be in the same
cable, with the appropriate precautions. There are some restrictions
on emergency lighting and fire alarm circuits, but these are to
enable them to continue working for as long as possible if other
cables have caught fire.

The regulations do draw attention to other standards on preventing
interference between such circuits.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

This is quite possible if your house uses a TN-S or IT supply where
the earth is remote from your neutral incomer. There will probably be
other properties on the same transformer and you could be reading
their volt drop in the neutral.

John

On Sun, 21 Oct 2007 09:39:32 -0700, chrisj.doran wrote:

On 21 Oct, 16:30, David WE Roberts wrote:

I have an arrangement of two sockets side by side in a fancy double wall
box.
One socket is a single 13 amp 3 pin, the other is a single round pin 3 pin
(like the old 5 amp IIRC).

Round-pin sockets are commonly used for lighting (table or standard
lamp) switched from elsewhere. Does it become live when you turn on
the room light? Is there an extra wire inside the light switch? Or a
mystery switch somewhere that appears to do nothing?

Spot on - finally got round to testing it and it is switched from the
mystery switch from a pair of switches on the wall.

I now have this urge to buy some round pin plugs and fit them to lamps
just so I can use it. I may however restrain myself (or be restrained by
my style consultant).

I was a little confused because the switch was connected to a completely
different cable (3 + E) which I usually associate with multiple switches
for one lighting circuit.

Now if I only knew what the disconnected 1.0mm T&E floating in the back of
the box used to do........

In article ,
David WE Roberts wrote:
I was a little confused because the switch was connected to a completely
different cable (3 + E) which I usually associate with multiple switches
for one lighting circuit.

Now if I only knew what the disconnected 1.0mm T&E floating in the back
of the box used to do........

Are there two table light circuits and multiple sockets? If so the extra
wire could be the second circuit - allows you to group things after
installation. It's exactly what I did when wiring this place.

--
*If a parsley farmer is sued, can they garnish his wages?

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