Breaking into a ring for a socket

[andyBenn2]

Hi
Would really appreciate some advice.
I am looking to add a socket in a ring for computer bits and pieces.
We had an extension build on the house, which has left 4 twin and earth cables running through a loft space right past where I want to add the socket. These are 2.5mm and come from the consumer unit which was replaced as part of the work.
Now the extension only has lighting and sockets so I presume that the 4 cables are 2 rings, one for each lighting and sockets, but there is no way to know which.
So if I am adding in a junction box to take the spur from does it matter if I use the lighting or socket ring as I have a 50/50 until I have cut the wire, and assume it makes no difference if which end of the ring I would be taking from ( that's actually too obvious to be asking)
Thanks
Andy

 

[Taylortwocities]

If it's a ring then - by definition - it doesn't have an end!

You must NOT use the lighting circuit for sockets.

What you must do is to absolutely 100% be sure that you have identified the correct circuit and that it is indeed a ring final and not lighting, heating, immersion or some other circuit.

Lighting and socket ring final circuits generally use different sized cable, so that would be the first step in identification/

From the loft you should be able to identify where the cables dive down the wall to sockets below. They should go down vertically to the socket location.

 

[andyBenn2]

Thanks for quick reply
Thought that it would probably be a no go for lighting supply just wasn't 100% as the wires are all 2.5 and so capable.
Sorry on the 'end' comment I meant which of the 2 ends of each of the 2 rings, which clearly doesn't matter, as long as it's the right ring.
Anyway the problem is that these 4 cables come through a crawl space into the extension, so I cannot see any take off from the 4 wires. They enter and leave as a bundle of 4.
Do electricians have a meter of some sort to detect the magnetic field in a wire so that you can pull the trip on the lighting ring and see which wires are is still live to get the socket ring.
Thanks
Andy

 

[ericmark]

Before doing any work we have to isolate and a MCB does not switch neutral so does not isolate so with domestic has to be main isolator although often we don't follow rules to letter so getting the wrong cable would not be a danger as it would be dead.

There are injectors which can put a signal down a wire but where cables are bunched together these are not 100%. The same applies to a voltage stick. So normally we would use a voltage stick to identify the cable but we would not rely on the reading we got we would isolate all once identified and then test once cut to verify correct one.

Google "Volt Stick" there are loads made around £10 to £15 but remember do not rely on result after using one.

 

[andyBenn2]

Got it, thanks again, great forum
Andy

 

[PrenticeBoyofDerry]

Would really appreciate some advice.

okay may repeat some info already given by respected forum memebers though.

I am looking to add a socket in a ring for computer bits and pieces.
We had an extension build on the house, which has left 4 twin and earth cables running through a loft space right past where I want to add the socket. These are 2.5mm and come from the consumer unit which was replaced as part of the work.
Now the extension only has lighting and sockets so I presume that the 4 cables are 2 rings, one for each lighting and sockets, but there is no way to know which.

Never presume, I would be surprised to find a lighting circuit on 2.5mm cable.
Using a little investigation and the correct testing equipment, can help in finding out what this cables power.
By using a good quality voltage pen/stick and switching circuits on and off, will go some way into confirm what circuits the cables are for.

So if I am adding in a junction box to take the spur from does it matter if I use the lighting or socket ring as I have a 50/50 until I have cut the wire, and assume it makes no difference if which end of the ring I would be taking from ( that's actually too obvious to be asking)

You cannot use the lighting circuit for sockets, as that will cause an overload issue. A standard junction box/boxes must be located so they can be easily accessed for maintenance, inspection and testing.
Also cable routing, needs to be position in permitted safe zones if the cable is to be buried within the fabric of the building.
Did the new CU have RCD protection for this socket circuit, as newly buried cable and socket outlets will now require this.

 

[andyBenn2]

Just to round this off.
I bought a voltage stick from maplin and with a little switching on and off located the socket supply and added in a junction box in the crawl space so easy to get to. It is on rcd.
Socket now Live and powering our computer etc rather than the trail of extension leads around the room.

Feeling very happy.
Thank you all again

 

[JBR]

Just to round this off.
I bought a voltage stick from maplin and with a little switching on and off located the socket supply and added in a junction box in the crawl space so easy to get to. It is on rcd.
Socket now Live and powering our computer etc rather than the trail of extension leads around the room.

Feeling very happy.
Thank you all again

Oh dear. Give it a few minutes and they'll all be here to tell you that voltage sticks are crap!

I bought one and find it useful.

 

[riveralt]

Just to round this off.
I bought a voltage stick from maplin

Oh dear. Give it a few minutes and they'll all be here to tell you that voltage sticks are crap!
I bought one and find it useful.

There is no problem in using these voltage detectors as long as you follow the safe isolation procedure.
I use one on a regular basis - no problems.

 

[PrenticeBoyofDerry]

Oh dear. Give it a few minutes and they'll all be here to tell you that voltage sticks are crap!
I bought one and find it useful.

I doubt they will!
They are very useful addition to the tool box and often help determine the cables of circuit, providing they are used correctly.
I wouldn't trust my life with one and would always carry out safe isolation procedures prior to cutting in to the cable and if there is any doubt, complete isolation of the installation would need to take place.

 

[EFLImpudence]

Feeling very happy.

On, no. I can't abide people being happy.

 

[PrenticeBoyofDerry]

Feeling very happy.

I hope "very happy" is not a name he uses for his thingy!
I know some get quite excited over their DIY accomplishments.

 

[ban-all-sheds]

Oh dear. Give it a few minutes and they'll all be here to tell you that voltage sticks are crap!

I bought one and find it useful.

For something like that yes.

As a device for proving dead so that you don't kill yourself, no.

 

[JohnW2]

They are very useful addition to the tool box and often help determine the cables of circuit, providing they are used correctly.

I agree.

I wouldn't trust my life with one and would always carry out safe isolation procedures prior to cutting in to the cable and if there is any doubt, complete isolation of the installation would need to take place.

Again, I agree. However, what you've said (and I agree with) effectively means that one always does have to adopt 'complete isolation of the installation' before cutting into a cable which has ben identified 'only' by use of a voltstick, doesn't it (since there will never be absolute certainty)?

Kind Regards, John