Set Square wrote:

There is a limit (can't remember what it is!) to the permitted number of
outlets on a single ring - but you probably won't exceed that unless the
ring has already been extended.

The limit is actually based on maximum floor area (100m^2) served by the
circuit, rather than a number of sockets as such. However, while this
should not be exceeded, you should still design the circuit taking into
account likely loads. So in a kitchen you may decide that a ring of only
10m^2 is "full"

My understanding is that any such work now comes under the provisions of
Part P of the Building Regs - and that, legally, the work needs to be
certified by a qualified electrician - or by Building Control if they are
capable! Many competent DIY-ers choose to ignore this - particularly if
there's no obvious evidence as to *when* the work was carried out.

Adding a socket to an existing circuit counts as a "minor work" IIRC and
hence is not notifiable.

--
Cheers,

John.

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Christian McArdle wrote:

I suspect it is written like that so that the OP can continue to use his
system (with an RCD) without having the power disconnected by overzealous
contractors/maintenance people. It really isn't that unsafe, provided that
the circuit conductors passed their continuity tests with the expected
numbers.

Not wishing to alarm Grant any more, but one thing I have not seen
mentioned yet is performing an insulation resistance check on the
current circuit either. Since it sounds as if the place is wired with
"older" cables, that could be a another potential problem area.

--
Cheers,

John.

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Not wishing to alarm Grant any more, but one thing I have not seen
mentioned yet is performing an insulation resistance check on the
current circuit either. Since it sounds as if the place is wired with
"older" cables, that could be a another potential problem area.

Unlikely, though. PVC is pretty durable.

However, given that only one circuit was used for the entire house, it is
possible that it has been running close to design current at various times,
which may have degraded the insulation more than it might otherwise. Apart
from this, I'd expect PVC installed even 50 years ago to be in serviceable
condition.

Obviously, a periodic test should really involve an insulation test. And it
seems that the entire installation could benefit from one.

Christian.

P. R. Brady dropped a zero in his message. He was correct at first with
7/029 as the name but that is seven strands of 0.029 of an inch or 29
thousandths of an inch.

Chris.

Richard Conway wrote:
Christian McArdle wrote:
The only real chance of problems is if you sell the house and lie on the
form

Or potentially if somebody got injured or worse as a result of the work
and an investigation highlighted that the work was done illegally.

Don't they just call you up to investigate and fix the results, and claim
that it was just a freak accident?

John wrote:
"Grant" wrote in message
...

Hi,

I want to extend the ring mains in my (1930's) house to add two double
sockets to a room. I've got the floorboards up and know where the new
cable needs to go. However, the thing that's stopping me going ahead is
the fact that the existing cable appears to be ever so slightly thicker
than the 2.5mm^2 that I was going to use. It is also multi(6)-stranded
instead of single-stranded. Is this to be expected with older wiring (I
believe a rewiring was done in the 70's)? There is a 32A MCB at the fuse
box so I thought that 2.5mm^2 would do the job but having seen the
existing wire I now have doubts. I don't want to weaken the installation
by using wire that is too thin.

After a bit of Googling it seems that 4mm^2 cable might be used in a
radial installation but I disconnected the wire between two sockets in the
room and they both still worked - does this allow me to conclude that I
have a ring mains? Also, 4mm^2 cable doesn't seem to be available from
B&Q, etc. - the next size up is 6mm^2.

Maybe the fact that I'm having to ask these questions suggests that I
should get in an electrician?!



It sounds like 7/.029 cable which was the forerunner of 2.5 solid conductor
and ws usually tinned copper conductors.
A simple solution of just using 2.5mm T&E to extend it is possible but
ignores the ramifications of cicuit protective conductor sizing (earth
conductor) and fault currents. However I suspect most of the run of the mill
sparkys might do just that.
4mm cable is readily available from half decent suppliers and some
wholesalers might even be willing to cut lengths for you.
For a fuller answer we would need to know what earthing arrangements apply
to your installation and an idea of possible cable lengths involved. You
have already advised us that you have a 32A MCB but can you tell us if it a
type B or otherwise? If the protection is problematic it might be possible
to use a 32A RCBO but we need answers first



Hi,

I have checked the old wire, and yes, it has seven conductors in it (I
had previously indicated that I thought it had six).

I plan to replace 3 metres of the existing wire (there isn't very much
slack between the two sockets it currently joins) and add another length
across the room (2 metres) to a new socket. Then another 3 metres to
another socket, finally completing the ring with existing cable which I
will cut about 1.5 metres off.

The 32A MCB has "Type 2" written on it and the CU is an old brown
plastic Wylex one (other MCBs in the CU have "Type B" written on them).
Can I get an RCBO for this or is a new CU required?

Cheers,
Grant

The 32A MCB has "Type 2" written on it and the CU is an old brown
plastic Wylex one (other MCBs in the CU have "Type B" written on them).
Can I get an RCBO for this or is a new CU required?

Do they look like:

http://www.tlc-direct.co.uk/Main_Ind...d_1/index.html
http://www.tlc-direct.co.uk/Main_Ind...nge/index.html

or like:

http://www.tlc-direct.co.uk/Main_Ind...nge/index.html
http://www.tlc-direct.co.uk/Main_Ind...s_2/index.html


Christian.

Christian McArdle wrote:
The 32A MCB has "Type 2" written on it and the CU is an old brown
plastic Wylex one (other MCBs in the CU have "Type B" written on them).
Can I get an RCBO for this or is a new CU required?


Do they look like:

http://www.tlc-direct.co.uk/Main_Ind...d_1/index.html
http://www.tlc-direct.co.uk/Main_Ind...nge/index.html

or like:

http://www.tlc-direct.co.uk/Main_Ind...nge/index.html
http://www.tlc-direct.co.uk/Main_Ind...s_2/index.html


Christian.





Hi Christian,

They look like these:

http://www.tlc-direct.co.uk/Main_Ind...nge/index.html

Cheers,
Grant

Owain wrote:
Grant wrote:

My understanding is that any such work now comes under the
provisions of
Part P of the Building Regs

I'm in Scotland - I think the regs are different here aren't they?
Even stricter?


The Regs are completely different and there is no Part P in Scotland.

The Building Standards (Scotland) have always been stricter in that
electric wiring has always had to be done to a safe and proper standard.
IEE Wiring Regulations are deemed to be a safe and proper standard, but
an equivalent is also acceptable.

What will change / has changed is the classes of person who is allowed
to sign off a certificate. It used to be anyone could sign a
certificate, now it has to be someone registered. However that only
applies where a certificate is required i.e. for notifiable work. I
*think* that wiring is not on its own notifiable and so you don't need a
certificate. If you were building an extension, which is notifiable,
then you would need a certificate as part of getting a building warrant.

Unlike English Part P, I don't think council building control officers
will inspect wiring for you.

The best thing would be to check with Building Control at the local
council.

Owain


After having spoken to Edinburgh City Council they tell me that strictly
speaking I should get a Building Warrant but they have never seen one
just for adding sockets and wouldn't expect me to apply for one. They
suggested I get a competent person to so the work for my own piece of mind.

I also asked about mixing old & new cable (different core colours) and
they said that that was perfectly OK as well. I had thought that I
needed to add a label to the CU stating that there was a mix but
apparently not. Maybe just in other parts of the UK?

Cheers,
Grant

Grant wrote:

I also asked about mixing old & new cable (different core colours) and
they said that that was perfectly OK as well. I had thought that I
needed to add a label to the CU stating that there was a mix but
apparently not. Maybe just in other parts of the UK?

The label is called up in an ammendment to BS7671 - so if you are not
obliged to work to that then there may be no requirement for it. Having
said that it sounds like common sense to add it anyway (not as important
on socket circuits, but makes more difference if you are changing any
lighting circuits with two way switches, where the three core and earth
colours could be a tad confusing!)

--
Cheers,

John.

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They look like these:


http://www.tlc-direct.co.uk/Main_Ind...nge/index.html

OK, to my knowledge, you won't find an RCBO to fit that. You'll need a
standalone RCD installed after the existing MCB.

Something like:

http://www.tlc-direct.co.uk/Products...h2slash30.html

Installed in one of these:

http://www.tlc-direct.co.uk/Products/BHCT2.html

Christian.

Christian McArdle wrote:
They look like these:



http://www.tlc-direct.co.uk/Main_Ind...nge/index.html

OK, to my knowledge, you won't find an RCBO to fit that. You'll need a
standalone RCD installed after the existing MCB.

Something like:

http://www.tlc-direct.co.uk/Products...h2slash30.html

Installed in one of these:

http://www.tlc-direct.co.uk/Products/BHCT2.html

Christian.



Christian,

Many thanks (again!) for the information.

Cheers,
Grant