How to identify a wire in loft

G

gizmogary

Hi, first post here but have read alot and think there is alot of good info here and help.

I am wanting to put a socket in my loft, I have been up there loads and have identified most wires like the lighting and other power cables. So far I have not been able to fine a wire that is part of a ring that I can use to get a socket up there. I have however found a wire that I know carries power (because of its thickness) but I do not know whether it is a spur or part of the ring, I cannot trace the wire to both ends without ripping holes in the walls beneath the loft. I can tell that one end goes down into a small partition wall, joined by wires for a light switch, and all there is on this wall is a light switch and a single socket, checking the socket it is not a spur. The other end of the cable disappears down a void at the house wall. The house only has 1 ring for the sockets and i suspect that this wire could be bringing the ring from downstairs upstairs, and if so I can put a junction box in the loft and use this. But is there any way I can test this wire and see for sure if this is part of a ring or a spur from somewhere...

Sorry if that was long, wanted all info in there :)

thx :)
 
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Firstly identify and label the fuses/MCBs in your consumer unit.

Get one of the contactless voltage indicators. Like this
http://www.sparksdirect.co.uk/volt-stick-230-instant-voltage-tester-p-4620.html

Its then a simple job to turn off the circuits one by one and see when the voltstick stops showing that a voltage is present, or not.

NOTE:
In most houses there are only lighting circuits in the loft.
What do you need the socket for? 3KW fire or a TV amp?

NOTE2
DO NOT use the voltstick to determine that the circuit has been isolated if you are doing actual work on the wires. Check out the Safe Isolation section in the WIKI.
 
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I have however found a wire that I know carries power (because of its thickness)
They all carry power, from 1mm² upwards...


but I do not know whether it is a spur or part of the ring,
Or even if it's part of a socket circuit.


I cannot trace the wire to both ends without ripping holes in the walls beneath the loft.
Then you're going to struggle to know what it is.


checking the socket it is not a spur.
How can you tell?

What checks did you do?


The other end of the cable disappears down a void at the house wall. The house only has 1 ring for the sockets and i suspect that this wire could be bringing the ring from downstairs upstairs, and if so I can put a junction box in the loft and use this.
You must not make alterations on the basis of what you suspect, i.e. guesswork.


But is there any way I can test this wire and see for sure if this is part of a ring or a spur from somewhere...
Yes.

Get a low-ohm meter and a proper voltage indicator (e.g. a Martindale VI13700).

With all of the power turned off (confirmed by the voltage indicator) remove the ring final conductors from the CU and verify that it is a proper ring as per the tests here:

http://www.tlc-direct.co.uk/Book/8.4.2.htm

Then cut the cable, see if you lose ring continuity.
 
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G

gizmogary

I have however found a wire that I know carries power (because of its thickness)
They all carry power, from 1mm² upwards...
Sorry, I meant mains socket power rather than lighting power.

but I do not know whether it is a spur or part of the ring,
Or even if it's part of a socket circuit.
Nearly 99% sure it is socket circuit, all other lighting circuits use smaller wire and anything that is mains socket is the proper 2.5mm cable.


I cannot trace the wire to both ends without ripping holes in the walls beneath the loft.
Then you're going to struggle to know what it is.


checking the socket it is not a spur.
How can you tell?

What checks did you do?
Took the socket out, 2 sets of wires, just how a socket looks on a ring. If it was a spur I would have expected only 1 set of wires (1x live, neutral, earth)


The other end of the cable disappears down a void at the house wall. The house only has 1 ring for the sockets and i suspect that this wire could be bringing the ring from downstairs upstairs, and if so I can put a junction box in the loft and use this.
You must not make alterations on the basis of what you suspect, i.e. guesswork.
Obviously i'm not going to do anything until I really know what this cable is, that's why i'm here ;)


But is there any way I can test this wire and see for sure if this is part of a ring or a spur from somewhere...
Yes.

Get a low-ohm meter and a proper voltage indicator (e.g. a Martindale VI13700).

With all of the power turned off (confirmed by the voltage indicator) remove the ring final conductors from the CU and verify that it is a proper ring as per the tests here:

http://www.tlc-direct.co.uk/Book/8.4.2.htm

Then cut the cable, see if you lose ring continuity.

Thanks for all the help and suggestions/advice so far.
Been thinking more, and as a bit of a brutal test i thought of cutting power, cutting this cable, making the ends safe, turning power back on and seeing if i've lost anything other than this socket on the partition, if the ring loses continuity then this cable must be part of the ring and i can then put a junction box in... or go the way of getting a voltage indicator...

Thanks thought :)
 
G

gizmogary

do you have wooden floors??

Wooden chipboard stuff upstairs, concrete downstairs. Can't take boards up upstairs as they go under partition walls etc due to the way the house was built.
 
G

gizmogary

NOTE:
In most houses there are only lighting circuits in the loft.
What do you need the socket for? 3KW fire or a TV amp?

Wanted to stay away from running from lighting circuit if poss, not planning on running anything high watts/amps at the moment but may in the future.
 
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i thought of cutting power, cutting this cable, making the ends safe, turning power back on and seeing if i've lost anything
Do not do this. If it is a ring you will not loose anything (although I suppose that would prove something). Follow advice above.
 
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Nearly 99% sure it is socket circuit, all other lighting circuits use smaller wire and anything that is mains socket is the proper 2.5mm cable.

It could be many other circuits that you cannot / must not / should not connect to.

Could be the feed for the immersion heater, a radial circuit for an outbuilding, a separated feed for a specific appliance (eg hob/oven/freezer).

Its no good being 1% unsure. That is the way to disaster.
 
G

gizmogary

Totally agree where you're coming from. I know there is at least 1 socket looking cable that is actually a direct feed for the house alarm.

More investigation and testing needed.
 
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Do the same tests that I suggested, but instead of cutting the mystery cable disconnect it at that socket.
 

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