Spur is not a spur?

[PatMoo]

Hi guys,

I'm hoping you can help me: I have a single socket in my living room which I plan to move and whilst I'm moving it, change it to a double. However, I had a rummage under the floorboards and noted there was a single cable serving the socket. So it's a spur, I thought. Since I'm running coax and network cables in the living room I'm getting a lot of floorboards up anyway, so I thought I'd wire the new double socket into the ring and simply remove the old spur.

This is where I get confused. I started tracing the cable serving the "spur" to find out which socket in the living room serves it and to my surprise, the cable disappears out of the living room and onto the landing. So then I took some boards up on the landing and discovered the cable then heads into my office. I traced it about 4m into the office (I'm reluctant to get any boards up in there because I've just a brand new floor laid!) before figuring it must be coming from downstairs - I redid the electrics in my office last year so I know it's not being served from a socket in there. My office is above the garage, though, which is where the fusebox is located.

Is it possible that this single socket is fed directly from the consumer unit with a single cable? If so, why would that be? Judging by the cable and the plaster around the socket, I think it's original, not a recent addition to the room. What I'd really like to know is: can I simply snip the cable off and terminate it in a junction box?

Thanks all, any help much appreciated...

 

[PrenticeBoyofDerry]

You can't just snip it and put it in JB if you are going to hide the JB under the floor as it must be left accessible. Ideally the circuit should be made dead and cable removed.
But you are wanting to use this circuit for alterations and addition of new double outlet, so seems pointless!
More investigatiuon is needed.
There is a chance that it is a radial served by the CU.
Best way to find out which circuit it belongs to would be to switch the MCBs or pull the fuse in you CU/fuse box.
When the socket goes dead you know which breaker is serving the socket and any other sockets that may be on the same circuit.
Once you have done this post back and inform us of the breaker/fuse size and the size (CSA) of the cable the breaker/fuse is protecting and the number of cables(line/live/reds if old colours) terminated at the fuse

 

[ericmark]

The question is:- Is it a spur or radial?
So what is the difference?
A radial is a wire protected by a fuse or MCB to the rating of the cable used at it's origin.
A spur is where the fuse protecting the cable is at the end of the run (In the plug for example) and is limited to 3 meters.

433.2.2 The device protecting a conductor against overload may be installed along the run of that conductor if the part of the run between the point where a change occurs (in cross-sectional area, method of installation, type of cable or conductor. or in environmental conditions) and the position of the protective device has neither branch circuits nor outlets for connection of current-using equipment and fulfils at least one of the following conditions:
(i) It is protected against fault current in accordance with the requirements stated in Section 434
(ii) Its length does not exceed 3 m, it is installed in such a manner as to reduce the risk of fault to a minimum, and it is installed in such a manner as to reduce to a minimum the risk of fire or danger to persons (see also
Regulation 434.2.1).

So step one is to find out which fuse/MCB/RCBO feeds the cable. Likely if 25A or less and the cable is 2.5 mm sq or more then it is a radial.

If the protection device is 32A then likely a spur (unless either mineral cable or over 2.5 mm sq).

Cable is rated according to how it is run, except with flex there is no such thing as 20A cable. So there is no fixed answer unless we know exactly what cable and how it is run.

However where it is found that a final ring has been broken and one can't repair it. Then to reduce the fuse/MCB size to 16, 20, or 25A according to cable type and run is a common way around the problem.

However if you intend to change things in the consumer unit do be aware that Part P will come in and it may be cheaper not to DIY.