two wires to socket, but not part of ring?

[freeflyer]

Hi all, mid eighties built house, and currently have two sockets in the bedroom, and ideally i need three (or four is poss).

I checked one socket, three wires, so thats no good to take the spur from. I checked the other, two wires, great ! But when i disconnected the two lives from this socket and powered back up (just to check) all sockets in the house were still working. I know that this perhaps could also have been the first of two sockets on an existing spur, but not if all sockets in the house were okay after disconnection?

So, what can this two wire socket be part of?

 

[Spark123]

You don't appear to understand the concept of a ring - it is a basically loops of wire which start and ends at the consumer unit looping to each socket (installed on the ring*) on the way, so there is always two paths for current to flow. If you check the end to end resistance of the phase, neutral and earth using a multimeter set to ohms range at the socket - if it is on the ring you should see a low resistance.

* this excludes unfused spurs which is why you have 3 wires behind one socket.

You can add one accessory per spur from the ring, this may be a single or a double socket. Any more then you'll either need to install a fused spur unit and wire more sockets from that or divert the ring.

 

[freeflyer]

aha thanks, yes i understand what you mean now. Disconnecting the two lives will do nothing to the other sockets, as they are still being fed from one or the other side of the ring., ie all i've broken is the feed to this socket.

I was going from the following, which was written in a book i have to test a two wire socket is part of the ring...

"disonnect the two live cores from their terminal on the socket and seperate them. Restore power, and check whether other outlets on the circuit still have power.
If all outlets on the circuit are now dead, you know that the disconnected outlet is on the main circuit and you can connect your spur to it. If only one other out let is dead, you have found an intermediate outlet on a two outlet spur."

Now i see this doesnt make sense.

 

[Spark123]

If it is on the ring then yes you would see both the red wires are both live, it is better however to test with the power off testing the end to end resistance of the reds, the blacks and the earths. This also proves there are no breaks in the earth, the neutral and the live conductors.

 

[freeflyer]

okay thanks..

so, lets assume this is a standard socket on the ring. If i add a fused spur off this, can i then run a single intermediate socket, followed by a double on this spur?

Ie it goes - current socket > new fused spur parelleled off it > single socket > Double socket.

 

[Spark123]

Yes, as the both the sockets will be protected by the 13A fuse in the fused spur unit.

 

[freeflyer]

great stuff thanks for the help

 

[sparkyspike]

What was the book called? Sounds like it needs burning.

 

[BS3036]

What was the book called? Sounds like it needs burning.

disonnect the two live cores from their terminal on the socket and seperate them. Restore power, and check whether other outlets on the circuit still have power.
If all outlets on the circuit are now dead, you know that the disconnected outlet is on the main circuit and you can connect your spur to it.

Probably a typo, change 'w' to 't'.

 

[ban-all-sheds]

Seriuosly, freeflyer, what book is it?

 

[freeflyer]

its a general DIY book, useful sometimes, a lot of it is basic stuff but even so, you'd think they do their research correctly..

http://www.dorlingkindersley-uk.co....rSrchSql=diy/DIY_(2nd_edition)_Julian_Cassell


Spark123, with this resistance check between the two ends, i'm essentially just doing a continuity check, yes? and any resistance will just be from the wire itself running round the ring?

 

[Spark123]

Yes
Make sure everything is unplugged to avoid it giving false readings, the Live to Live end to end resistance should be the same as the neutral to neutral (as the cable is the same size), the earth to earth resistance should be slightly higher (about 1.67x higher) as the earth wire is slightly smaller.

 

[freeflyer]

good stuff thanx